JPS59144749A - Schiff base having megative dielectric anisotropy - Google Patents

Abstract

NEW MATERIAL:The compound of formula I (R is 1-10C alkyl). EXAMPLE:2-Cyanobenzylidene-2-cyano-4-pentylaniline. USE:A liquid crystal composition having negative dielectric anisotropy and stable to moisture, air, heat, light, etc. PREPARATION:The compound of formula I can be prepared by heating 2-cyano benzaldehyde of formula II and 2-cyano-4-alkylaniline of formula III in toluene in the presence of a catalytic amount of p-toluene-sulfonic acid.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a novel liquid crystal compound having negative dielectric anisotropy,
and a liquid crystal composition containing the same.

Liquid crystal display elements utilize the optical anisotropy and dielectric anisotropy of liquid crystal materials, but depending on the display format, TN
It is divided into various types such as type (twisted nematic type), DS type (dynamic scattering type), guest-host type, and DAP type.
The properties of liquid crystal materials suitable for each use vary. However, all liquid crystal materials have in common that they need to be stable against moisture, air, heat, light, etc., and they are also required to exhibit a liquid crystal phase over as wide a temperature range as possible, centered around room temperature. ing. However, at present, there is no single compound that satisfies these conditions, and the current situation is to use liquid crystal compositions obtained by mixing several types of liquid crystal compounds and non-liquid crystal compounds.

Recently, guest display, which is a color LCD display method, has been
Host-type liquid crystal display devices have started to attract attention. Although this uses a mixture of liquid crystal and dye, a liquid crystal having a positive dielectric anisotropy of 3% lJ and a negative dielectric anisotropy is used.

Therefore, there is a need for liquid crystal compounds or liquid crystalline compounds having various properties, good compatibility, and negative dielectric anisotropy that can be used as constituent components of liquid crystals. Here, the seven-component compound and QJ
Although it does not exhibit a liquid crystal phase by itself, it can be used in combination with a liquid crystal compound of [10] to form a constituent component of a liquid crystal composition.
It is a useful compound in

An object of the present invention is to provide a novel liquid crystal compound suitable for such uses.

That is, the present invention relates to 2'-cyanobenzylidene-2-cyano-4-alkylaniline, which is represented by the general formula ← (in which R represents an alkyl group having 1 to 10 carbon atoms), and It is a liquid crystal composition containing at least one of them.

Although the compound of the present invention does not exhibit a liquid crystal phase, it exhibits a dielectric anisotropy value of about -5, so it can be used for guest-host type display devices by mixing with other nematic liquid crystals. A usable liquid crystal composition having negative dielectric anisotropy can be obtained. Furthermore, by combining it with one having a positive dielectric anisotropy value, it can be used in a dual frequency method type display element.

The method for producing the compound of the present invention is as follows: 2-cyanobenzaldehyde and 2-cyano-4-alkylaniline are heated in toluene with a catalytic amount of p-toluenesulfonic acid to obtain the desired compound. The chemical formula is (1) (R in the above formula is the same as above) The compound of the present invention will be explained in more detail with reference to Examples below.

Example 1 [Production of 2-cyanobenzylidene-2-7ano-4-pentylaniline] 2-cyanobenzaldehyde 2.30 ? (17,6
mmoz) 2-cyano 4-pentylaniline 3
．． 30,? (17,6 mn, o/ ) was placed in a flask and dissolved in toluene somz. This p-
) Add about 20 ml of luenesulfonic acid and add 3 ml of luenesulfonic acid while stirring.
The mixture was heated to reflux for an hour. Next, when toluene is distilled off under reduced pressure, an oily substance remains, which is recrystallized with ethanol.
3.36# of 2'-anopenzylidene-2-7ano-4-pentylaniline, which is the target product, was obtained (yield: 63
．． 4 yen). The melting point of this thing is 85.1-8! 5.6℃
Met.

Similarly, from 2-7anobenzaldehyde and 2-cyano-4-hebutylaniline, 2'-cyanobenzylidene-2-cyano-4-hebutylaniline (melting point 85.9
-86.4°C) was produced.

Example 2 (Usage Example) Ester-based nematic liquid crystal composition Rikunn 5-4- (L Engineering The viscosity at 9.20°C is 1.8.5 Cp. A guest-host cell was prepared by adding one dose of commercially available dye G-224 manufactured by Merck & Co. to this mixture and sealing it in a cell.The threshold voltage of the cell was measured and found to be 3.80V.

Next, the compounds of the present invention, 5 parts of 2'-cyanobenzylidene-2-cyano-4-pentylaniline, 9 parts of 2'-cyanobenzylidene-2-cyano-4-heptylaniline, 5 parts of 2'-cyanobenzylidene-2-cyano-4-heptylaniline,
A liquid crystal composition was prepared consisting of 90 parts of FN-4 and 90 parts of the above FN-4. Its N-work setting 34.2 ℃Δeke-1,02,
The viscosity at 20°C is 3 B.
When a host type liquid crystal cell was made and its threshold voltage was measured, it was found to be significantly lower than 3.60V.

that's all 6-

Claims (2)

[Claims] (1) 2-cyanobenzylidene-2-cyano- represented by the general formula (in the above formula, R represents an alkyl group having 1 to 10 carbon atoms)
4-alkylaniline. (2) 2-cyanobenzylidene-2-cyano- represented by the general formula (in the above formula, R represents an alkyl group having 1 to 10 carbon atoms)
A liquid crystal composition containing at least one package of 4-alkylaniline.