Chiral cyclohexyl compounds

Details Chiral cyclohexyl compounds Chiral cyclohexyl compounds

1997-01-16

1998-12-29

Kelly, C. H.

Compositions

Liquid crystal compositions

Containing nonsteryl liquid crystalline compound of...

25229961, 25229966, 568835, 558431, C09K 1930, C09K 1934, C09K 1912, C07C 2920

Patent

active

058536132

DESCRIPTION:

BRIEF SUMMARY
This application is based on PCT/GB95/01538, filed Jun. 29, 1995 and GB 9412709.9, filed Jun. 29, 1994.
This invention relates to novel chiral compounds suitable for use in liquid crystal mixtures and their inclusion in liquid crystal devices.
Liquid crystals can exist in various phases. In essence there are three different classes of liquid crystalline material, each possessing a characteristic molecular arrangement. These classes are nematic, cholesteric and smectic. A wide range of smectic phases exists, for example smectic A and smectic C. Some liquid crystal materials possess a number of liquid crystal phases on varying the temperature, others have just one phase. For example, a liquid crystal material may show the following phases on being cooled from the isotropic phase:--isotropic--nematic--smectic A--smectic C--solid. If a material is described as being smectic A then it means that the material possesses a smectic A phase over a usefull working temperature range.
Most liquid crystal devices incorporate a mixture of materials selected to give desired operating characteristics. The present invention provides liquid crystal materials suitable for incorporating in a wide variety of mixtures to provide the desired characteristics suitable for use in a number of devices.
U.S. Pat. No. 4,846,998 discloses liquid crystal compounds comprising cyclohexane derivatives.
WO 86/05485 discloses liquid crystal compounds comprising cyclohexane derivatives. The cyclohexane may be substituted such that a chiral centre is present however the nature of the synthetic procedures described is such that only racemic mixtures are described. Mol. Cryst. Liq. Cryst. 1990, vol. 191, pp259-67 also discusses liquid crystal compounds comprising cyclohexane derivatives--this document is limited to use of a methyl substituent on the cyclohexane and there appears to be no discussion of stereochemistry.
According to this invention there are provided compounds having a general Formula I: ##STR1## wherein A, B, C, D are independently selected from any of phenyl, pyridine, pyrimidine, cyclohexyl, substituted phenyl and at least one of the cyclohexyl groups: ##STR2## must be present: wherein X may be any one of OH, OR.sub.3, R.sub.3, CH.sub.2 OR.sub.3 F, Cl, OCF.sub.3, CF.sub.3, CH.sub.2 F, CHF.sub.2, CN, may contain a chiral centre; may contain a chiral centre or R.sub.2 is H; ##STR3## wherein Y may be individually selected from F, Cl or CN and y may be 1-4; X.sub.1, X.sub.2 and X.sub.3 are linking groups and are independently selected from single bond, CH.sub.2 O, OCH.sub.2, COO, OCO, CH.sub.2 CH.sub.2 ;
Preferably those groups A, B, C, D which are not given by the cyclohexyl groups: ##STR4## are phenyl or substituted phenyl; Preferably X is selected from any one of OH, OR.sub.3, R.sub.3, F, CF.sub.3, CH.sub.2 F, CHF.sub.2, CN, wherein R.sub.3 is a methyl group or an ethyl group; alkyl or alkoxy or H; single bond, CH.sub.2 O or OCH.sub.2 ;
Compounds of Formula I can be included in a material, the material being a mixture of compounds.
The materials of this aspect of the invention may be used in many of the known forms of liquid crystal display devices, for example chiral smectic electro-optic devices. Such a device may comprise a layer of liquid crystal material contained between two spaced cell walls bearing electrode structures and surface treated to align liquid crystal material molecules. The liquid crystal mixtures may have many applications including in ferroelectric, thermochromic and electroclinic devices.
Ferroelectric smectic liquid crystal materials, which can be produced by mixing an archiral host and a chiral dopant, use the ferroelectric properties of the tilted chiral smectic C, F, G, H, I, J and K phases. The chiral smectic C phase is denoted S.sub.C * with the asterisk denoting chirality. The S.sub.C phase is generally considered to be the most useful as it is the least viscous. Ferroelectric smectic liquid crystal materials should ideally possess the following characteristics: low viscosity, controllable spontaneous

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Chemical Abstracts 117:181967 & JP 04069352. (1995).
Chemical Abstracts 114:133345 & Mol. Cryst. Liq. Cryst (1990). 191, 259-67.
Chemical Abstracts 112:169628 & Zh.Org.Khim.(1989), 25 (11), 2399-402.
Chemical Abstracts 107:166170 & Zh. Orl. Khim. (1987), 23(6), 1268-73.
Molecular Crystals and Liquid Crystals vol. 191, (1990) pp. 259-267 Karamysheva "Liquid crystalline phenylcyclohexanes with a lateral methyl substituent".

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