JPH0819075B2 - Optically active cyanobiphenyl compound - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a specific optically active compound, and more particularly to a cyanobiphenyl compound having an asymmetric carbon atom-containing alkoxy group.

Liquid crystals have been applied as various electro-optical elements and have been put to practical use for displays such as watches and calculators. Most of the currently practically used liquid crystal display devices utilize the dielectric alignment effect of twisted nematic liquid crystals and cholesteric liquid crystals. However, recently, other types of liquid crystal display methods have been actively developed, and STN methods and cholesteric / nematic phase transition type display methods are also used.

The liquid crystal compositions used in these liquid crystal display devices are adjusted to have respective helical pitches by introducing an optically active substituent into a nematic liquid crystal or by adding an optically active substance. For example, a Schiff base type liquid crystal made of p-alkoxybenzaldehyde and (+)-p-amino-2-methylbutylbenzene is known. Further, as the optically active substance to be added, 4-
(2-Methylbutyloxy) -4'-cyanobiphenyl is known, but since this compound has a long twist pitch of cholesteric liquid crystal, it has a drawback that a large amount of compound is required to obtain desired physical properties. there were.

The present inventors have found that the crystal-liquid crystal phase transition temperature useful as a component of the liquid crystal mixture for a display device is low, and when giving a cholesteric phase, the liquid crystal-isotropic liquid phase transition temperature is high and the helical pitch is short. As a result of extensive studies to find a compound, when a novel optically active cyanobiphenyl compound represented by the following formula (I) has a remarkably low crystal-liquid crystal phase transition temperature and the compound gives a cholesteric phase, Since the liquid crystal-isotropic liquid phase transition temperature is high, it has been found that the compound is extremely suitable for use for the above purpose.

Hereinafter, the present invention having the above gist will be described in more detail.

The compound represented by the general formula (I) is, for example, 4-
It can be easily prepared by a well-known etherification reaction in which a halide or tosylate of hydroxy-4′-cyanobiphenyl and an optically active alcohol is reacted in the presence of an alkali compound.

Next, the present invention will be described with reference to examples. However, the present invention is not limited by the following examples.

Example 1 Synthesis of (R)-(4-cyano-4 ′-(6-chloro-3-methylhexyloxy) biphenyl 0.45 g of 55% sodium hydride and 10 ml of dimethylformamide were taken, and 4- () was cooled with ice. 4'-cyanophenyl)
A solution of 1.50 g of phenol and 3 ml of dimethylformamide was added dropwise, and the mixture was stirred at room temperature for 1 hour. Then (R) -6-
Chloro-3-methylhexanol ([α] _D = + 0.63 °
A solution of 2.58 g of p-toluenesulfonic acid ester (27 ° C., C = 1, chloroform solution) and 3 ml of dimethylformamide was added dropwise, and the mixture was stirred at 80 ° C. for 2 hours. After cooling the reaction solution
It was poured into 200 ml of ice water and extracted with diethyl ether.
After drying, the residue obtained by removing the solvent was purified using a silica gel column using n-hexane / diethyl ether (85/15) as a developing solvent to obtain (R) -4-cyano-4′-.
(6-chloro-3-methylhexyloxy) biphenyl 2.
Obtained 85 g.

As a result of infrared spectroscopic analysis, the obtained product had the following characteristic absorptions and was confirmed to be the target product.

2930cm ^-1 (s), 2880cm ^-1 (m), 2220cm ^-1 (s), 1600cm ^-1 (vs), 1
^{490cm -1 (vs), 1250cm -1} (vs), 1180cm -1 (s), 820cm -1 (vs), 5
60cm ^-1 (w), 530cm ^-1 The (m), the following optical rotation of the resulting product.

[Α] _D = + 5.31 ° (27 ° C., C = 1, CHCl ₃ solution) As a result of observing the phase morphology of this compound with a polarization microscope, the following phase transitions were confirmed.

This compound is a nematic liquid crystal ZLI-15 manufactured by Merck.
Pitch was measured in a Kano wedge-shaped cell by mixing 10% with 65, and the results are shown in the table below.

As a comparative example, C-15 manufactured by BDH was used. Pitch (μm) 30 ℃ 40 ℃ 50 ℃ 60 ℃ The above compound 2.1 2.2 2.2 2.4 C-15 7.2 7.6 8.0 8.5 by BDH The above compound has a shorter helical bitch than the C-15 of the comparative example, and moreover the temperature dissimilarity. It is clear that there are few.

Claims (1)

[Claims] 1. An optically active cyanobiphenyl compound represented by the following formula (I):