JPH0329058B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel liquid crystal material having weak positive dielectric anisotropy and a liquid crystal composition containing the same. Display elements using liquid crystals are 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. is the most widely put into practical use. Namely, they include TN (twisted nematic) type, DS type (dynamic scattering type), guest・
There are host type, DAP type, etc., and each type has different properties depending on the requirements of the liquid crystal material used. 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 the natural world.Currently, there is no single substance that satisfies such conditions, and several types of liquid crystal substances or non-liquid crystal substances are available. It is put into practical use by mixing liquid crystal materials. These substances include water, light,
It is required to be stable against hot air, etc.
Furthermore, it is desirable that the threshold voltage and saturation voltage required to drive the display element be as low as possible, and that the viscosity be as low as possible in order to increase the response speed. Furthermore, in order to widen the liquid crystal temperature range toward higher temperatures, it is necessary to use a liquid crystal substance with a high melting point as a component, but liquid crystal substances with a high melting point generally have a high viscosity, and therefore the liquid crystal composition containing it also has a high viscosity. As a result, the response speed of liquid crystal display elements that can be used at high temperatures, for example, up to about 80° C., particularly at low temperatures, has tended to become significantly slower. The present inventors discovered a liquid crystal substance that has low viscosity and makes it difficult for crystals to precipitate when added as a component of a composition, and thus arrived at the present invention. That is, the present invention is based on the general formula (In the above formula, R represents an alkyl group having 2 to 8 carbon atoms,

[Formula] and

[Formula] is Re

[Formula] or

[Formula] is shown,

[Formula] is

In the case of [formula]

【ceremony

[Formula]. ) and a liquid crystal composition containing the ester derivative having a 3-trifluoromethylphenyl group. The compounds of the present invention have a high clearing point, for example, one of the compounds of the present invention, trans-4-(trans-4'-propylcyclohexyl)cyclohexanecarboxylic acid-3-trifluoromethylphenyl ester, has a liquid crystal phase. It has a nematic clearing point of 44.8°C, and its addition as a component of the composition lowers the viscosity of the composition, resulting in a nematic clearing point of 44.8°C.
This can be done without lowering the clearing point too much. Further, although the dielectric anisotropy value of the compound of the present invention is about +1, it does not change the threshold voltage and saturation voltage of the composition so much. It also has good stability against moisture, heat, light, etc. Next, a method for producing the compound of the present invention will be described. The ester derivatives are reacted with 3-trifluoromethylphenol in the presence of the corresponding carboxylic acid chloride and pyridine to form the corresponding ester derivatives. Shown as a chemical formula, (In the above formula, R,

【formula】

[Formula] is the same as above) The compounds of the present invention will be explained in more detail with reference to Examples below. In each example, the crystal phase is C, the smectic phase is Sm,
The transparent phase is abbreviated as I, the melting point as mp, and the nematic phase as N. Example 1 [Production of 4-pentylbiphenyl-4'-carboxylic acid-3-trifluoromethylphenyl ester] 1.6 g of 3-trifluoromethylphenol was dissolved in 10 ml of pyridine, and while stirring well, 4-pentyl Biphenylyl-4'-carboxylic acid chloride
Added 2.9g. This reaction solution was left overnight, poured into 100 ml of water, and an oily substance was extracted with 100 ml of toluene.
The toluene layer was washed with 6N-HCl, then with 2N-NaOH, and then with water until it became neutral, filtered, and the toluene was distilled off under reduced pressure. The remaining crystals were recrystallized from ethanol to obtain the desired product, 4-pentylbiphenyl-4'-carboxylic acid-3-trifluoromethylphenyl ester. Yield 2.1g, yield 51%, C-Sm point 68.6℃,
The Sm-I point was 76.1°C. Examples 2 to 4 4-Pentylbiphenylyl in Example 1
The desired compound was obtained by carrying out the same procedure as in Example 1, using 0.01 mol of the corresponding carboxylic acid chloride in place of the 4'-carboxylic acid chloride. The results are shown in Table 1 together with Example 1.

[Table] Example 5 (Usage example) [4-pentyl-4'-cyanobiphenyl 51% (weight, same below) [4-heptyl-4'-cyanobiphenyl 32% [4-octyloxy-4'-cyanobiphenyl]
The N-I point of a liquid crystal mixture with a composition of 17% is 44℃, and the viscosity is
The dielectric anisotropy value was 40 cp and +12.4 at 20°C. When it is used in a twisted nematic cell, the threshold voltage is 1.65V and the saturation voltage is 2.31V. 90 parts by weight of this liquid crystal mixture is the N-1 point of the liquid crystal mixture to which Example 3 of the present invention and 10 parts by weight of trans-4-(trans-4'-heptylcyclohexyl)cyclohexanecarboxylic acid-3-trifluorophenyl ester are added. The temperature rose to 46°C, the dielectric anisotropy value was +11.2, and the viscosity was 39 cp at 20°C. Also, when using a twisted nematic cell, the threshold voltage was 1.60V, and the saturation voltage was slightly lower at 2.30V.

Claims (1)

[Claims] 1. General formula (In the above formula, R represents an alkyl group having 2 to 8 carbon atoms, and [formula] and [formula] represent [formula] or [formula], respectively, but if [formula] is [formula], then [formula] is [Formula]) An ester derivative having a 3-trifluoromethylphenyl group represented by: 2 General formula (In the above formula, R represents an alkyl group having 2 to 8 carbon atoms, and [formula] and [formula] represent [formula] or [formula], respectively, but if [formula] is [formula], then [formula] is [Formula].) A liquid crystal composition comprising at least one ester derivative having a 3-trifluoromethylphenyl group represented by the following formula.