JPH0256346B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel liquid crystal material exhibiting a liquid crystal phase over a wide temperature range and having negative dielectric anisotropy, and a liquid crystal composition containing the same.

Display elements using liquid crystals have come to be widely used in watches, calculators, etc. This liquid crystal display element utilizes the properties of optical anisotropy and dielectric anisotropy of liquid crystal materials, and there are three liquid crystal phases: nematic liquid crystal phase, smectic liquid crystal phase, and cholesteric liquid crystal phase, among which nematic liquid crystal is used. The one that has been put into practical use is the most widely used. In other words, there are TN (twisted nematic) types, DS (dynamic scattering) types, guest-host types, DAP types, dual-frequency method types, etc., and the properties required of the liquid crystal materials used for each type are different. Ru. But in any case,
It is desirable that the liquid crystal substances used in these display elements exhibit a liquid crystal phase over as wide a range as possible in nature, but at present there is no single substance that satisfies such conditions, and several types of liquid crystal substances or Currently, materials that can be put to practical use are obtained by mixing non-liquid crystal materials. In addition, these substances are susceptible to moisture, light,
Of course, it must be stable against heat, air, etc., and in addition, the threshold voltage and saturation voltage required to drive the display element must be as low as possible, and the viscosity must be increased to increase response speed. It is desirable that it be as low as possible. Incidentally, in order to display positive color in a liquid crystal display device, a liquid crystal composition having a negative dielectric anisotropy value is required, but many of the compounds having a negative dielectric anisotropy value known so far are The liquid crystal temperature range was narrow, the viscosity was high, and the stability was poor. However, the compound of the present invention has a Δε of about -2, has low viscosity, exhibits a liquid crystal phase, and has good compatibility with other liquid crystals. It can also be added to liquid crystal compositions with positive dielectric anisotropy values for use in dual frequency methods. Furthermore, even when used in a TN type, the drive voltage value can be lowered.

That is, the compound of the present invention has the general formula (In the above formula, R and R' represent an alkyl group having 1 to 10 carbon atoms) 2-cyano-4-substituted-1-[trans-4-(trans-4-substituted-cyclohexyl)cyclohexyl]benzene and a liquid crystal composition containing the same.

Next, a method for producing the compound of the present invention will be described.

First, 4-substituted-[trans-4-(trans-4-substituted-cyclohexyl)cyclohexyl]benzene shown in JP-A-57-165328 was iodized with iodine and periodic acid in an acetic acid solvent, and then dimethyl Cyanation with cuprous cyanide in formamide yields the desired 2-cyano-4-substituted-1-
[trans-4-(trans-4-substituted-cyclohexyl)cyclohexyl]benzene is obtained.

The above is expressed as a chemical formula as follows.

Hereinafter, the method for producing and using the compound of the present invention will be explained in more detail with reference to Examples.

Example 1 [2-cyano-4-methyl-1-[trans-
4-(trans-4-butylcyclohexyl)
Production of cyclohexyl]benzene] First, 3.12 g (0.01 mol) of 4-methyl-1-[trans-4-(trans-4-butylcyclohexyl)cyclohexyl]benzene was added to 50 ml of acetic acid and 5 ml of water.
ml and add 1 ml of concentrated sulfuric acid. This includes iodine
1.01g (0.004 gram atom) and 0.45g periodic acid
(0.002 mol) and refluxed for 6 hours. After cooling, water
Add 300ml and filter the precipitate under reduced pressure. Wash the filtered material with 500 ml of cold water and recrystallize it with 100 ml of acetone.
Dissolve 0.4 g (0.9 mmol) of the obtained crystals in 30 ml of dimethylformamide and add 0.25 g of cuprous cyanide.
(1.3 mmol) and refluxed for 6 hours. After cooling, add 50 ml of ammonia water (28%) and extract with 50 ml of toluene. The toluene layer is washed with water until the washing liquid becomes neutral, and then the toluene is distilled off under reduced pressure to produce new toluene.
Recrystallize in 20ml. The obtained crystals are the target 2-cyano-4-methyl-1-[trans-4-(trans-4-butylcyclohexyl)cyclohexyl]benzene. Yield 0.2g, melting point 93.0-94.9
℃, nematic clearing point (N-I point) 75.2℃. This product was confirmed to be the desired compound by IR and NMR.

Other compounds of formula () can also be produced in the same manner.

Example 2 (Use example 1) Ester-based nematic liquid crystal composition Rixon
The N-I point of FN-45 (manufactured by Chitsuso Co., Ltd.) is 63℃, △ε
is -0.9, and the viscosity at 20°C is 19 cp. A guest-host cell was created by adding 1% of commercially available dye G-224 manufactured by Merck & Co. into the mixture, and the threshold voltage was measured.
It was 3.80V.

A liquid crystal composition prepared by adding 10 parts of 2-cyano-4-methyl-1-[trans-4-(trans-4-butylcyclohexyl)cyclohexyl]benzene shown in Example 1 of the present invention to 90 parts of Rixon FN-45 above. The N-I point of the product is 64°C, Δε is -1.0, and the viscosity at 20°C is 23 cp. A guest-host cell was made with 1% of the dye G-224 added as before, and its threshold voltage was measured and found to be 3.3V.

Example 3 (Use Example 2) Trans-4-propyl-(4'-cyanophenyl)cyclohexane 24% Trans-4-pentyl-(4'-cyanophenyl)cyclohexane 36% Trans-4-heptyl-(4'-cyanophenyl) The nematic temperature range of a liquid crystal composition consisting of 25% cyclohexane and 15% trans-4-pentyl-(4″-cyanobiphenyl)cyclohexane is from −10 to
The temperature was 71.9°C, the viscosity at 20°C was 28 cp, the threshold voltage was 1.8V, and the saturation voltage was 2.5V, which was sealed in a 10 μm thick TN cell with a transparent electrode. 85 parts of this was added to 2-cyano-4-methyl-1-[trans-4-(trans-4-butylcyclohexyl)cyclohexyl] shown in Example 1 of the present invention.
Nematic composition of liquid crystal composition containing 15 parts of benzene
The clearing point was 67.1℃. The threshold voltage sealed in the above cell was 1.6V, and the saturation voltage was 2.1V, indicating that it can be driven at a lower voltage.

Claims (1)

[Claims] 1. General formula (In the above formula, R and R' represent an alkyl group having 1 to 10 carbon atoms) 2-cyano-4-substituted-1-[trans-4-(trans-4-substituted-cyclohexyl)cyclohexyl]benzene . 2 General formula (In the above formula, R and R' represent an alkyl group having 1 to 10 carbon atoms) 2-cyano-4-substituted-1-[trans-4-(trans-4-substituted-cyclohexyl)cyclohexyl]benzene A liquid crystal composition characterized by containing at least one type of.