JPH0157107B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel liquid crystal compound having a large positive dielectric anisotropy value and a liquid crystal composition containing the same. Liquid crystal display elements utilize the optical anisotropy and dielectric anisotropy of liquid crystal materials, and display methods include TN type (twisted nematic type), DS type (dynamic scattering type), and guest/host type. There are various types of liquid crystals, such as type, DAP type, and White-Taylor type, and each type requires different properties of the liquid crystal material used. For example, depending on the type of display element,
As a liquid crystal material, a material having a positive dielectric anisotropy Δε is required, a material having a negative dielectric anisotropy is required, or a material having an intermediate value is suitable. However, in any case, the liquid crystal material used must exhibit a liquid crystal phase over as wide a temperature range as possible and be stable against moisture, heat, air, light, etc. At present, there is no single compound that satisfies all of these conditions, and the current state of affairs is to mix several types of liquid crystal compounds and non-liquid crystal compounds to obtain compounds that can withstand practical use. Recently, there has been an increasing demand for liquid crystal display elements that can be driven particularly at low voltages, and in order to meet such demands, liquid crystal compositions with a large Δε are usually required. In general, a liquid crystal composition with an arbitrary △ε value is △ε
It is obtained by appropriately mixing a compound with a positive value and a compound with a negative value. Therefore, in order to obtain a liquid crystal composition with a large Δε value, it is sufficient to use a component with a Δε value as large as possible. It must be something that expands the range or at least does not narrow it down. In order to meet these objectives, the present inventors have already developed the general formula (In the above formula, R represents an alkyl group or an alkoxy group having 1 to 10 carbon atoms,

【formula】

He invented a 3-chloro-4-cyanophenyl ester of carboxylic acid represented by the following formula ([Formula] represents a benzene ring or a cyclohexane ring) and filed a patent application (Japanese Patent Application No. 39166/1983). However, recent demands for improved performance of liquid crystal display elements have become more sophisticated, and compounds with lower viscosity and stability against heat, light, air, and water are required. The compounds of the present invention meet these requirements. That is, the present invention is based on the general formula (In the above formula, R represents an alkyl group having 2 to 5 carbon atoms) 3-fluoro-4-cyano-1-
This is a liquid crystal composition characterized by containing [trans-4-(4-trans-substituted cyclohexyl)cyclohexyl]benzene and at least one kind thereof. The compound of the present invention has a large dielectric anisotropy value of about +30, has a relatively low viscosity, is stable against heat, light, air, and water, and exhibits a liquid crystal phase over a wide temperature range. It is suitable as a component constituting a liquid crystal composition having a large Δε value, low viscosity, and a wide liquid crystal temperature range. Next, a method for producing the compound of the present invention will be described. First, 3-[trans-4-(trans-4-substituted cyclohexyl)cyclohexyl]fluorobenzene (a compound known in JP-A-57-75939) is reacted with acetyl chloride in carbon disulfide in the presence of aluminum chloride, An acetylated product was obtained. This is then reacted with sodium hypobromite in dioxane to give a carboxylic acid compound, which is reacted with thionyl chloride in toluene to give an acid chloride compound. This is reacted with aqueous ammonia to form an acid amide compound, and then dehydrated with thionyl chloride to obtain the desired 3-fluoro-4-cyano-1-[trans-4-(trans-4-substituted cyclohexyl)cyclohexyl]benzene. Ta. The above is expressed as a chemical formula as follows. Hereinafter, the compounds of the present invention will be explained in more detail with reference to Examples. Example 1 [Production of 3-fluoro-4-cyano-1-[trans-4-(trans-4-propylcyclohexyl)cyclohexyl]benzene] 3-[trans-4-(trans-4-propylcyclohexyl)cyclohexyl] 5 g of fluorobenzene was dissolved in 50 ml of carbon disulfide, 4 g of aluminum chloride was added, and 3 g of acetyl chloride was added dropwise at below 5° C. with stirring. After dropping, reduce the temperature to 35℃
After 2 hours, cold hydrochloric acid was added and the resulting precipitate was washed with ice water. It was recrystallized from a mixed solvent of acetone and toluene to produce 4-[trans-4-
(Trans-4-propylcyclohexyl)cyclohexyl]-2-fluoroacetophenone was obtained. Next, suspend 0.7 g of this material in 50 ml of dioxane and keep it below 10°C. Sodium hypobromite prepared by adding 1.6 g of bromine to 2 g of sodium chloride and 30 ml of ice water was added dropwise thereto with stirring.
After dropping the entire amount, the temperature was raised to 35°C and stirring was continued for 5 hours. After cooling, the mixture was made acidic with 6N hydrochloric acid, and the precipitate deposited was filtered and washed with water. This is 4-[trans-4-
(trans-4-propylcyclohexyl)cyclohexyl]-2-fluorobenzoic acid. This was recrystallized from acetic acid, 0.6 g of the dried product was dissolved in 20 ml of toluene, 2 g of thionyl chloride was added, and 3
Refluxed for an hour. After excess thionyl chloride was distilled off under reduced pressure, the residual oil was poured into aqueous ammonia, and the resulting precipitate was filtered, washed with water, and further recrystallized from toluene. This is 4-[trans-4-(trans-4-propylcyclohexyl)cyclohexyl]-2-fluorobenzoic acid amide. 0.4 g of this product was dissolved in 10 ml of dimethylformamide and 10 ml of toluene, 2 g of thionyl chloride was added, and the mixture was refluxed for 4 hours. After cooling, add cold water and separate and extract with 50 ml of toluene. After washing the oil layer with water until it became neutral, toluene was distilled off under reduced pressure, and the remaining oil was recrystallized from a mixed solvent of toluene and acetone. The obtained crystalline substance is the target 3-fluoro-4-cyano-1
-[Trans-4-propylcyclohexyl)cyclohexyl]benzene. Yield 0.1g. Crystal - smectic point 53.8℃, smectic - nematic point 89.8℃, nematick - clear point 207℃. 3-[Trans-4-] by the same operation as above.
(trans-4-propylcyclohexyl)cyclohexyl] instead of the corresponding 3-[trans-4-(trans-4
-substituted cyclohexyl) cyclohexyl] using fluorobenzene to obtain the desired 3-fluoro-4-
Cyano-1-[Trans-4-(Trans-4-
Substituted cyclohexyl)cyclohexyl]benzene can be produced. 3-fluoro-4-cyano-1-[trans-
4-(trans-4-butylcyclohexyl)cyclohexyl]benzene, crystalline nematic point (C-N point) 35.6℃, nematic clearing point (N-
Point I) 202℃. Example 2 (Usage example) Trans-4-propyl-(4'-cyanophenyl)cyclohexane 28% Trans-4-pentyl-(4'-cyanophenyl)cyclohexane 42% Trans-4-heptyl-(4'-cyanophenyl)cyclohexane The NI point of a liquid crystal composition having a composition of 30% is 52°C, and Δε is +10.5. This liquid crystal composition has a cell thickness of 10 μm.
When sealed in a TN cell (twisted nematic cell), the operating threshold voltage is 1.53V and the saturation voltage is 2.12V.
It was hot. The viscosity was 23 cp at 20°C. To 90 parts of this liquid crystal composition, the 3-
Fluoro-4-cyano-1- [trans-4-
(trans-4-propylcyclohexyl)cyclohexyl] The N-I point of a liquid crystal composition to which 10 parts of benzene was added was 66°C, and Δε was +12.5. When this was made into a TN cell similar to the above, The threshold voltage is 1.40V, the saturation voltage is reduced to 1.90V, and the viscosity is
Although it rose to 29 cp, this level does not pose any practical problem. As described above, by using the compound of the present invention, the operating voltage of the display element could be lowered, and the operating temperature range could also be expanded.

Claims (1)

[Claims] 1. General formula (In the above formula, R represents an alkyl group having 2 to 5 carbon atoms) 3-fluoro-4-cyano-1-
[trans-4-(trans-4-substituted cyclohexyl)cyclohexyl]benzene. 2 General formula (In the above formula, R represents an alkyl group having 2 to 5 carbon atoms) 3-fluoro-4-cyano-1-
[trans-4-(trans-4-substituted cyclohexyl)cyclohexyl]benzene at least 1
A liquid crystal composition characterized by containing seeds.