JPH06256247A - 4-alkoxy-3,5-difluorobenzene derivative - Google Patents

Abstract

PURPOSE:To provide a low-viscosity new compound high in N-I point, useful as an electro-optical liquid crystal display material, esp. as a liquid crystal material for active matrices. CONSTITUTION:The compound of formula I (R<1> is 1-10C alkyl or alkenyl; L and M are each single bond or CH2CH2; R<2> is 1-10C alkyl), e.g. 1[trans-4-(trans-4- propylcyclohexyl)cyclohexyl]-3,5-difluoro-4-methoxybenzene. The compound of the formula I can be obtained by the following process: a 1-alkoxy-4- bromo-2,6-difluorobenzene of formula II is made to react with magnesium to form a Grignard reactive agent, which is then made to react with a 4-(trans- alkylcyclohexyl)cyclohexanone of formula III (R<a> is 1-7C alkyl) followed by dehydration, hydrogenation, and then resolution or isomerization. By adding this compound of the formula I to a liquid crystal composition, the upper limit temperature for the liquid crystal phase clan be raised without raising the viscosity and threshold voltage.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel compound which is a 4-alkoxy-3,5-difluorobenzene 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 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 It is important to note that the three are wide.

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, respectively.) As can be seen from this formula, in order to lower the threshold voltage. It is necessary to reduce the elastic constant of the liquid crystal material or increase the dielectric anisotropy.

However, a liquid crystal compound having a large dielectric anisotropy generally has a large polarity, and when added to a composition, it is quite difficult to obtain a high specific resistance value and a high voltage holding ratio. Therefore, a liquid crystal material having a small elastic constant is required for such purpose.

However, most of the bicyclic compounds having a small elastic constant have a tendency to significantly lower the maximum temperature of the liquid crystal phase of the composition by adding them.

On the other hand, in order to expand the temperature range of the liquid crystal phase of the liquid crystal composition to a high temperature range, it is necessary to add a compound having a high tricyclic or tetracyclic liquid crystal maximum temperature. However, many compounds having such a high maximum temperature have a large elastic constant, and when added to the composition, they tend to increase the threshold voltage.

Without lowering the maximum temperature of the liquid crystal phase,
As a compound capable of lowering the threshold voltage, a compound having a trifluorophenyl group is known. However, the maximum liquid crystal phase temperature of this compound is 1
Since it is not so high as 00 ° C. or less, it was difficult to greatly increase the liquid crystal phase maximum temperature of the composition. Moreover,
Since this compound has a relatively high melting point and has a smectic phase in the low temperature range of the nematic phase, adding a large amount of this compound causes a problem in the stability of the nematic phase in the low temperature range of the composition. Therefore, in reality, the amount added is considerably limited. Further, regardless of the driving method, it is further required that the viscosity of the liquid crystal material is low in order to achieve a high-speed response.

As described above, it is quite difficult to obtain a liquid crystal composition having a low viscosity, a high maximum temperature of a liquid crystal phase and a low threshold voltage.

[0012]

The problem to be solved by the present invention is to improve the liquid crystal of the composition by adding the compound in accordance with the above purpose without substantially increasing the viscosity and the threshold voltage of the composition. Provided is a compound that raises the maximum temperature of a phase, and a liquid crystal composition containing the compound, which has a low viscosity, a high maximum temperature of the liquid crystal phase, and a low threshold voltage. Especially.

[0013]

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

[0014]

[Chemical 2]

(In the formula, R ¹ represents a linear alkyl group having 1 to 10 carbon atoms or a linear alkenyl group, preferably a linear alkyl group having 1 to 10 carbon atoms, and particularly preferably Preferably, it represents a linear alkyl group having 1 to 5 carbon atoms, and L and M are each independently a single bond or -C.
H ₂ CH ₂ —, at least one of which represents a single bond, preferably both represent a single bond, and R ² represents a linear alkyl group having 1 to 10 carbon atoms, preferably 1 carbon atom. 5 represents a straight chain alkyl group, and the cyclohexane ring represents a trans configuration. ) Is provided.

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

[0017]

[Chemical 3]

(In the formula, each R ^a independently has 1 carbon atom.
Represents a straight-chain alkyl group having from 7 to 7 and R ^b has 2 carbon atoms.
~ 7 represents a straight-chain alkenyl group, and R ² has the same meaning as in formula (I). The compound represented by the formula () is preferable, and among these, the compound represented by the general formula (Ia) is particularly preferable.

The compounds represented by the general formulas (Ia) to (Id) can be produced, for example, as follows.

[0020]

[Chemical 4]

(In the formula, R ² has the same meaning as in formula (I), and X represents a chlorine atom, a bromine atom, an iodine atom or a leaving group such as a p-toluenesulfonyl group.)
First, 4-bromo-2,6-difluorophenol obtained by brominating commercially available 2,6-difluorophenol is reacted with a compound of the general formula (a) in the presence of a base,
1-alkoxy-4-bromo-2,6 of the general formula (II)
-Difluorobenzene can be obtained.

[0022]

[Chemical 5]

(In the formula, R ² has the same meaning as in formula (I), and R ^a has the above-mentioned meaning.)
The compound of the general formula (II) is reacted with magnesium to obtain a Grignard reaction agent,
Reaction with (trans-4-alkylcyclohexyl) cyclohexanone, followed by dehydration and hydrogenation, gives a mixture of isomers having different configurations of the central cyclohexane ring. These can be separated or isomerized with a base to obtain the compound of the general formula (Ia) of the present invention.

[0024]

[Chemical 6]

(In the formula, R ² has the same meaning as in the general formula (I), and R ^a and X have the aforementioned meanings.)
Here, in the general formula (Ia), 1- [trans-4- (trans-4-alkylcyclohexyl) cyclohexyl] -3,5-difluoro-4 in which R ² is a methyl group.
-Methoxybenzene is demethylated with hydrobromic acid or trimethylsilyl iodide to give 4- [trans-4- (trans-4-alkylcyclohexyl) cyclohexyl] -2,6-difluorophenol, which is treated with a base and You may alkylate similarly using the compound of the said General formula (a).

Further, instead of the compound of the general formula (III), the general formula (IV)

[0027]

[Chemical 7]

Using 4- (trans-4-alkylcyclohexyl) cyclohexaneethanal represented by the formula (wherein R ^a has the above-mentioned meaning) and using the compound of the general formula (Ib) in the same manner. You can

[0029]

[Chemical 8]

(In the formula, R ^a has the above-mentioned meaning and Ph represents a phenyl group.) Here, the compound of the general formula (IV) is, for example, as described above, the compound of the general formula (III) It can be easily obtained by reacting the Wittig reagent of formula (V) and then repeating the acid treatment step twice.

Further, by using 4- [2- (trans-4-alkylcyclohexyl) ethyl] cyclohexanone of the general formula (VI) instead of the compound of the general formula (III), the compound of the general formula (Ic) Can be obtained.

[0032]

[Chemical 9]

(In the formula, R ^a has the above-mentioned meaning.) Here, the compound of the general formula (VI) is, for example, as described above, trans-4-alkyl-1- (2-bromoethyl) cyclohexane is Grignard. It can be easily obtained by reacting this with a monoethylene acetal of cyclohexane-1,4-dione as a reactant, dehydration and hydrogenation, and then removing the acetal.

[0034]

[Chemical 10]

(In the formula, R ² has the same meaning as in the general formula (I).) Further, in place of the compound of the general formula (III), bicyclohexane-4 of the general formula (VII),
By similarly reacting with 4'-dione monoethylene acetal and finally removing the acetal, 4- [trans-4- (4-alkoxy-3,5-difluorophenyl) cyclohexyl of the general formula (VIII) is obtained. ] Cyclohexanone can be obtained.

[0036]

[Chemical 11]

(In the formula, n and m each independently represent an integer of 1 or more, but n + m ≦ 10, R ² has the same meaning as in formula (I), and Ph represents a phenyl group. .) Further, in the compound of the general formula (VIII),
By reacting the Wittig reagent of the general formula (V) n times as necessary, and further reacting with the Wittig reagent of the general formula (IX), a general formula (A) having a double bond at an arbitrary position of the terminal group ( The compound of Id) can be obtained.

When m ≧ 2, the obtained compounds are mainly cis isomers, but these compounds are isomerized to the trans isomers by an ordinary method such as light irradiation in the presence of a catalyst or a sensitizer. Is possible.

Table 1 shows typical examples of the compounds represented by the general formula (I) thus produced.

[0040]

[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 compound represented by the general formula (I) of the present invention is It is clear that it shows a nematic phase up to a high temperature range. Therefore, when it is added to a general-purpose host liquid crystal, its transition temperature can be raised to a high temperature range. Furthermore, since its melting point is extremely low and it does not show a smectic phase in a low temperature region, when a large amount of this compound is added, there is very little tendency for precipitation or appearance of a smectic phase. Moreover, as shown in the examples described later, there is almost no tendency to increase the threshold voltage or viscosity of the composition by addition.

Therefore, the compound represented by the general formula (I) of the present invention is suitable as a material of a field effect display cell such as a TN type or STN type in a state of a mixture with another nematic liquid crystal compound. Moreover, since a strong polar group such as a cyano group or an ester bond does not exist in the molecule, a large specific resistance value 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 further provides a liquid crystal composition containing at least one compound represented by the general formula (I) as a constituent. In the composition of the present invention, preferred representative examples of the nematic liquid crystal compound which can be used by mixing with the compound represented by the general formula (I) are, for example, 4-substituted benzoic acid 4-substituted phenyl ester and 4-substituted benzoic acid 4-substituted phenyl ester. 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 pyrimidine, 2- (4′-substituted biphenylyl) -5-substituted pyrimidine and the like can be mentioned.

The effects of the compounds of general formula (I) are, for example,
It is also clear from the following example. A matrix liquid crystal (A) currently widely used as a nematic liquid crystal material

[0045]

[Chemical 12]

(Wherein the cyclohexane ring represents the trans configuration and "%" means "% 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 viscosity of this composition at room temperature (20 ° C.) was 21.0 cP (centipoise).

A liquid crystal composition (M-1) comprising 80% by weight of the base liquid crystal (A) and 20% by weight of the compound (No. 1) in Table 1 was prepared. The maximum temperature of the nematic phase was 64 ° C. And rose considerably. Further, Δε was as small as 6.2. However, when V _th was similarly measured using this composition, it was 1.61 V, which was almost the same as that of the base liquid crystal (A), although Δε was reduced by nearly 10%. This is because the elastic constant (K) of the compound (No. 1) according to the present invention is 3 in consideration of the above formula.
It is considered that the ring compound is quite small. Furthermore, when the viscosity of the composition (M-1) at room temperature (20 ° C.) was measured, it was 20.7 cP, which was lower than that of the base liquid crystal (A). From this, (No.
It can be understood that the compound of 1) has a considerably low viscosity as a tricyclic compound.

On the other hand, instead of the compound of (No. 1), the compound of formula (R-
1)

[0049]

[Chemical 13]

A liquid crystal composition (N-1) comprising 20% by weight of the compound of 80% by weight and the same host liquid crystal (A) as 80% by weight was prepared. The compound of formula (R-1) has a structure similar to that of the compound of (No. 1) according to the present invention but does not have a fluorine atom, and the maximum temperature of the nematic phase is 200.2.
Although the temperature is very high at 18 ° C, it shows a smectic phase at 180.2 ° C or lower and the melting point is also very high at 175 ° C.

The maximum temperature of the nematic phase of the composition (N-1) was 79.7 ° C., which was considerably higher than that of the base liquid crystal (A). Further, Δε was 5.9, which was smaller than that of the base liquid crystal (A) and the composition (M-1). However, when V _th was measured in the same manner, it was 1.97 V, which was much higher than that of (M-1). From this, the elastic constant of the compound of formula (R-1) is as follows when compared with the compound of (No. 1):
Considered to be quite large. The viscosity of (N-1) at room temperature (20 ° C) was 23.6 cP, which was much higher than that of the base liquid crystal (A). Furthermore, when this (N-1) was left at room temperature, crystals were precipitated in a short time.

Next, instead of the compound (No. 1),
Formula (R-2) having a similar structure to the compound of (No. 1)

[0053]

[Chemical 14]

A liquid crystal composition (N-2) consisting of 20% by weight of the compound of the above and 80% by weight of the same base liquid crystal (A) was prepared. Here, the compound of formula (R-2) has a structure similar to the compound of (No. 1) according to the present invention, but has a trifluorophenyl group at the terminal, and the maximum temperature of the nematic phase is 93. It is considerably lower than the compound of 5 ° C and (No. 1), and the melting point is as high as 64 ° C.

The maximum temperature of the nematic phase of this composition (N-2) was 59.5 ° C., which was about 5 ° C. lower than that of (M-1), and Δε was as large as 7.3. From this, it can be understood that it is difficult to prepare a composition having a high maximum temperature of the nematic phase and a small Δε using the compound of the formula (R-2).

Next, among nematic liquid crystal materials, a host liquid crystal (B) particularly suitable for active matrix use.

[0057]

[Chemical 15]

(Wherein the cyclohexane ring represents the trans configuration) was prepared. This host liquid crystal (B) has 11
It exhibits a nematic phase at 6.7 ° C. or lower, Δε is 4.7, and the threshold voltage (V
_th ) was 2.43V.

70% by weight of this base liquid crystal (B) and (N
o. A liquid crystal composition (M-
When 2) was prepared, the maximum temperature of the nematic phase rose significantly to 125 ° C. Further, Δε was as small as 4.0. Similarly, when the threshold voltage was measured, 2.
55V and its rise was slight.

From the above, the compound represented by the general formula (I) raises the upper limit temperature of the liquid crystal phase without substantially increasing the viscosity and the threshold voltage (V _th ) of the host liquid crystal exhibiting the nematic liquid crystal phase. It is clear that it effectively raises.

[0061]

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, m represents a multiplet, and J represents a coupling constant. M ^{+ in} MS represents the parent peak.

"%" In the composition means "% by weight".

Example 1 1- [trans-4- (trans-4-propylcyclohexyl) cyclohexyl] -3,5-difluoro-4-methoxybenzene (N
o. Compound of 1) (1-a) Synthesis of 4-bromo-2,6-difluoroanisole

[0065]

[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 mixed solution, 27 g of bromine was added dropwise over 30 minutes. After the dropping was completed, an aqueous sodium hydrogen sulfite solution was added to decompose excess bromine, and the organic layer was separated. The organic layer was washed with water and then with saturated saline, and dehydrated and dried over anhydrous sodium sulfate.
The solvent was distilled off to obtain 28.6 g of crude crystals of 4-bromo-2,6-difluorophenol.

Next, 28.6 g of this 4-bromo-2,6-difluorophenol was dissolved in 150 ml of acetone, and 28 g of potassium carbonate was added to this solution. 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 the reaction solution to make it 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 brine, dehydrated and dried over anhydrous sodium sulfate, and the solvent was distilled off to give an oily 4
26.9 g of -bromo-2,6-difluoroanisole was obtained.

(1-b) 1- [trans-4- (trans-4-propylcyclohexyl) cyclohexyl]
Synthesis of -3,5-difluoro-4-methoxybenzene

[0069]

[Chemical 17]

4-bromo-2,6 obtained in the above (1-a)
26.9 g of difluoroanisole were dissolved in 140 ml of tetrahydrofuran (THF). TH this solution
It was added dropwise to 10 ml of F and 3.5 g of magnesium while gently maintaining the temperature at which 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 to the reaction mixture at 0.
It was added dropwise in 5 hours. After stirring for a further 3 hours, dilute hydrochloric acid was added and the reaction product was extracted with ethyl acetate. After evaporating the solvent of the extract, the residue 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 to room temperature, it was washed successively with saturated aqueous sodium hydrogen carbonate solution, water and saturated brine. After dehydration and drying with anhydrous sodium sulfate, the solvent was distilled off, and 1- [4- (trans-4-
Propylcyclohexyl) cyclohexen-1-yl]
39.6 g of crude crystals of -3,5-difluoro-4-methoxybenzene were obtained.

The total amount of this compound was 400 ml of ethyl acetate.
And palladium-carbon (4.0 g) were added, and catalytic reduction was carried out for 4 hours at room temperature under a hydrogen atmosphere at normal pressure. After the catalyst was filtered off, the solvent was distilled off to give a viscous oily substance 1-
[4- (trans-4-propylcyclohexyl) cyclohexyl] -3,5-difluoro-4-methoxybenzene was obtained. This was recrystallized from ethanol and purified to obtain 13.4 g of white crystals of 1- [trans-4- (trans-4-propylcyclohexyl) cyclohexyl] -3,5-difluoro-4-methoxybenzene. 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 ⁺ ).

Example 2 Synthesis of 1- [trans-4- (trans-4-propylcyclohexyl) cyclohexyl] -3,5-difluoro-4-propyloxybenzene (2-a) 2,6-difluoro- 4- [Trans-4
Synthesis of-(trans-4-propylcyclohexyl) cyclohexyl] phenol

[0073]

[Chemical 18]

1- [trans-4-obtained in Example 1
(Trans-4-propylcyclohexyl) cyclohexyl] -3,5-difluoro-4-methoxybenzene 2
7.2 g was dissolved in 560 ml acetic acid. 48 in this solution
800 ml of% 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 extract was washed with water until the aqueous layer became neutral, 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 2,6-difluoro-4- [trans-4- (trans-4-propylcyclohexyl) cyclohexyl].
18.4 g of phenol was obtained. (2-b) Synthesis of 1- [trans-4- (trans-4-propylcyclohexyl) cyclohexyl] -3,5-difluoro-4-propyloxybenzene

[0075]

[Chemical 19]

2.3 g of 2,6-difluoro-4- [trans-4- (trans-4-propylcyclohexyl) cyclohexyl] phenol obtained in (2-a) above.
Was dissolved in 5 ml of N, N-dimethylformamide (DMF), and this was added dropwise to 0.32 g of sodium hydride suspended in 40 ml of DMF. DMF10 was added to this solution.
1.31 g of propyl iodide dissolved in ml was added dropwise, and after completion of the addition, the mixture was heated under reflux for 8 hours. After cooling, add water,
The reaction product was extracted with toluene. After washing with water and saturated saline, the solvent was evaporated, the product was purified by silica gel column chromatography (hexane / toluene), and recrystallized from ethanol to give 1- [trans-4- (trans-4-. 2.55 g of white crystals of propylcyclohexyl) cyclohexyl] -3,5-difluoro-4-propyloxybenzene were obtained. Phase transition temperature: 55.5 ° C. (Cr → I), 158.5 ° C.
(N-I) MS: m / e = 378 (M ⁺ )

Example 3 Preparation of Liquid Crystal Composition (1) Base liquid crystal (A) having the following composition

[0078]

[Chemical 20]

(Wherein the cyclohexane ring represents the trans configuration) was prepared and showed a nematic (N) phase at 54.5 ° C. or lower. Further, the respective physical property values at 20 ° C. 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 Viscosity 21.0 cP

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

Maximum temperature of N phase (T _NI ) 64.0 ° C. Dielectric anisotropy (Δε) 6.2 Refractive index anisotropy (Δn) 0.094 Threshold voltage (V _th ) 1.61V Viscosity 20.7 cP

As described above, although the upper limit temperature (T _NI ) of the N phase has risen by about 10 ° C. and the dielectric anisotropy (Δε) has decreased on the contrary, the threshold voltage (V _th It is clear that) has hardly risen. Considering the above formula (1), the elastic constant (K) of the compound of (No. 1) is considered to be quite small. Furthermore, since the viscosity is rather low, it can be understood that the compound (No. 1) has a considerably low viscosity as a tricyclic compound. When this composition was left at a low temperature for a long time, no precipitation or the like was observed. Therefore, it is clear that the compound (No. 1) is also excellent in compatibility with conventional liquid crystal compounds.

Comparative Example 1 In Example 3, (No.
Instead of the compound of 1), a compound of formula (R-1) having a similar structure to the compound of (No. 1) but having no fluorine atom.

[0085]

[Chemical 21]

A liquid crystal composition (N-1) consisting of 20% of the compound of the formula (R-1) and 80% of the same host liquid crystal (A) was prepared using the compound of the formula (R-1). 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 ) 79.7 ° C. Dielectric anisotropy (Δε) 5.9 Refractive index anisotropy (Δn) 0.101 Threshold voltage (V _th ) 1.97 V Viscosity 23.6 cP

Thus, although the upper limit temperature (T _NI ) of the N phase is higher than that of (M-1), the threshold voltage (V _th )
Has a very high value as compared with the base liquid crystals (A) or (M-1). (N-1) dielectric anisotropy (Δε)
Is slightly smaller than (M-1), it is considered from the above formula (1) that the elastic constant of the compound of formula (R-1) is considerably larger than that of the compound of (No. 1). To be The viscosity of this composition at room temperature is 23.
Increased compared to 6 cP and (M-1). Furthermore, when the composition (N-1) was kept at 0 ° C., crystals were precipitated within 1 hour.

(Comparative Example 2) In Example 3, (No.
Instead of the compound of 1), it has a similar structure of (No. 1), but the terminal group is a trifluorophenyl group (R-
2)

[0090]

[Chemical formula 22]

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

Maximum temperature of N phase (T _NI ) 59.5 ° C. Dielectric anisotropy (Δε) 7.3 Refractive index anisotropy (Δn) 0.091 Thus,
The upper limit temperature (T _NI ) of the N phase is 5 degrees lower than that of (M-1), and the dielectric anisotropy (Δε) is also (M-1).
Clearly much larger.

Example 4 Preparation of Liquid Crystal Composition (2) Fluorine Base Liquid Crystal (B) Suitable for Active Matrix

[0094]

[Chemical formula 23]

(Wherein, the cyclohexane ring represents a trans configuration). This host liquid crystal (B) has 11
It showed a nematic (N) phase at 6.7 ° 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 ) 2.43V

A liquid crystal composition (M-2) comprising 70% of the base liquid crystal (B) and 30% of the compound (No. 1) obtained in Example 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 ) 125.0 ° C. Dielectric anisotropy (Δε) 4.0 Refractive index anisotropy (Δn) 0.092 Threshold voltage (V _th ) 2.55V

Thus, the upper limit temperature (T _NI ) of the N phase is 1
The threshold voltage has risen nearly 0 degrees, and the threshold voltage has hardly risen, although the dielectric anisotropy (Δε) has decreased.

The specific resistance value of this composition 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 at 98% or more. From the above results, (N
o. It can be understood that the addition of the compound of 1) can effectively increase the upper limit temperature of the nematic liquid crystal phase without substantially increasing the threshold voltage (V _th ) of the host liquid crystal.

[0101]

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. Therefore, it is also excellent in compatibility with the host liquid crystal that is currently widely used as a nematic liquid crystal. Moreover, by adding a small amount to the base liquid crystal, it is possible to effectively increase the upper limit temperature of the nematic liquid crystal phase without increasing the viscosity and the threshold voltage (V _th ). In addition, since there is no strong polar group in the molecule, a composition having a large specific resistance value 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 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, and R ² represents a linear alkyl group having 1 to 10 carbon atoms.). 2. The compound according to claim 1, wherein R ¹ is a linear alkyl group having 1 to 10 carbon atoms, and L and M are both single bonds. 3. A liquid crystal composition containing the compound represented by the general formula (I) according to claim 1.