JPH0150692B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to novel chlorine-containing organic compounds exhibiting positive dielectric anisotropy and liquid crystal compositions containing them. Liquid crystal display elements, which have recently come into widespread use, take advantage of the properties of dielectric anisotropy and optical anisotropy of liquid crystal materials. , cholesteric liquid crystal phase, among which display elements that utilize nematic liquid crystal phase include TN type, DS type, guest-host type, DAP type, etc. Also, display elements that utilize smectic liquid crystal phase include memory type display elements, etc. However, in any case, it is desirable for liquid crystal materials used in display elements to exhibit a liquid crystal phase over as wide a natural temperature range as possible, but there is no single compound that satisfies these conditions. It has not been found yet, but by mixing various substances, they have achieved their goal by creating something that can be put to practical use. Of course, these substances must also be stable against moisture, light, heat, etc.
Furthermore, it is advantageous in all respects to have as low a threshold voltage and saturation voltage as possible for driving a display element, but this usually requires a material with a large absolute value of dielectric anisotropy. However, the present inventors have found that although the dielectric anisotropy is smaller than that of conventionally commonly used cyano group-containing substances, the threshold voltage and saturation voltage are not high, and the nematic temperature range, moisture, The present invention was achieved by finding a compound that is stable against light and heat. That is, the present invention is based on the general formula (In the above formula, R represents an alkyl group having 1 to 10 carbon atoms) trans-4-(4'-substituted phenyl)
-Cyclohexanecarboxylic acid 4''-chlorophenyl ester and a liquid crystal composition containing at least one thereof. Most of the compounds themselves exhibit a nematic liquid crystal phase, but when mixed with other liquid crystal substances, the threshold voltage can be increased. Nematic operation without increasing saturation voltage
The clearing point (N-I point) can be raised. For example, 4-(4′-bentylphenyl)-cyclohexanecarboxylic acid 4″-chlorophenyl ester is heated at 92.1°C.
It exhibits a nematic phase at temperatures ranging from 138.7°C to 138.7°C, and can be mixed with biphenyl-based, phenylcyclohexane-based, ester-based, and Schiff-based liquid crystal compounds to create various practical liquid crystal compositions. Next, a method for producing compound (1) of the present invention will be described. First, trans-4-(4′-substituted phenyl)-cyclohexanecarboxylic acid was converted into trans-4-(4′-substituted phenyl)-cyclohexanecarboxylic acid with thionyl chloride.
(4′-substituted phenyl)-cyclohexanecarbonyl chloride and reacted it with p-chlorophenol in pyridine to produce trans-4-(4′-substituted phenyl)-cyclohexanecarboxylic acid 4″-chlorophenyl ester. .This can be expressed as a chemical formula. (In the above formula, R is the same as above.) The present invention will be explained in more detail with reference to Examples below. Example 1 [Production of trans-4-(4'-propylphenyl)-cyclohexanecarboxylic acid 4''-chlorophenyl ester] Trans-4-(4'-propylphenyl)-cyclohexanecarboxylic acid 12.3 g (0.05 mol) ), add 50 ml of thionyl chloride and heat to 70-80℃ and reflux.2
Since the mixture becomes homogeneous in ~3 hours, excess thionyl chloride is distilled off under reduced pressure. The residual oil is trans-4-
(4'-substituted phenyl)-cyclohexanecarbonyl chloride (acid chloride). This is added to 6.5 g (0.05 mol) of p-chlorophenol dissolved in 30 ml of pyridine with vigorous stirring. Add 30ml of toluene, leave it overnight, then pour into 500ml of water to separate the liquid. That toluene layer
3 times with 6NHCl, once with water, 3 times with 2NNaOH aqueous solution
After washing twice, the solution is washed with water until it becomes neutral, and then toluene is distilled off under reduced pressure to precipitate crystals. This crystal is recrystallized with ethanol to obtain the desired trans-
7.5 g of 4-(4'-propylphenyl)-cyclohexanecarboxylic acid 4''-chlorophenyl ester was obtained (yield 42%).The C-N point of this was 123.5-124.5.
℃, the N-I point was 149.1℃. Examples 2 to 4 [Production of trans-4-(4′-substituted phenyl)-cyclohexanecarboxylic acid 4″-chlorophenyl ester] In place of trans-4-(4′-propylphenyl)-cyclohexanecarboxylic acid in Examples Trans-4-(4'-substituted phenyl)-cyclohexanecarboxylic acid shown in Table 1 was prepared in exactly the same manner except that 0.05 mol of trans-4-(4'-substituted phenyl)-cyclohexanecarboxylic acid having another alkyl group was used. Acid 4″-chlorophenyl ester was prepared. These physical property values are shown in Table 1.

[Table] Example 5 (Usage example) 4-bentyl-4'cyanobiphenyl 45% 4-heptyl-4'cyanobiphenyl 29% 4-octyloxy-4'-cyanobiphenyl
The liquid crystal mixture having a composition of 15% 4-pentyl-4'-cyanoterphenyl 11% has an N-I point of 63.3 DEG C. and a dielectric anisotropy of +12.4. The thickness of this liquid crystal mixture is coated with silicon and assembled with two substrates with rubbed tin oxide transparent electrodes.
When the liquid crystal cell was sealed in a 10 μm cell and its characteristics were measured at 25°C, the threshold voltage was 1.65V and the saturation voltage was 2.31V. Trans-4 of Example 3 was added to 90 parts of this liquid crystal mixture.
The liquid crystal mixture to which 10 parts of -(4'-pentylphenyl)-cyclohexanecarboxylic acid 4''-chlorophenyl ester was added had an N-I point of 70.8°C and a dielectric anisotropy of +
In 11.0, encapsulate this in the same cell as in the previous case,
When we measured the characteristics of the liquid crystal cell under the same conditions, we found that
The threshold voltage is 1.70V, and the saturation voltage is 2.40V, and although the dielectric anisotropy has become smaller, the increase is slight.

Claims (1)

[Claims] 1. General formula (In the above formula, R represents an alkyl group having 1 to 10 carbon atoms) trans-4-(4'-substituted phenyl)
-Cyclohexanecarboxylic acid 4″-chlorophenyl ester. 2 General formula (In the above formula, R represents an alkyl group having 1 to 10 carbon atoms) trans-4-(4'-substituted phenyl)
- A liquid crystal composition containing at least one type of cyclohexanecarboxylic acid 4''-chlorophenyl ester.