The Secretary of State for Defence in Her Britannic Majesty's Government

The Secretary of State for Defence in Her Majesty'3 S Government of the

Jennifer Constant

George W Gray

Edward P Raynes

Damien Gerard McDonnell

Kenneth J Toyne

David Lacey

Adam Jackson

Richard M Scrowston

Lawrence Kam Chan

Madeline J Bradshaw

Amarjit Kaur Samra

Victoria Brimmell

Ibrahim G Shenouda

Ian A Shanks

Neil Carr

Hilal M Abdullah

Optically active compounds of formula (I), where X has a structure (II) and B is C.sub.1-12 alkyl, a chiral group or a group having a general structure (III), where R and R' are H, C.sub.1-12 alkyl, alkoxy, alkylcarbonyloxy, or alkoxycarbonyl, each ring (IV) and (V) is the same or different, A and D are single bonds or bridging groups, each a and d is 0 or 1; Z, Z' are CN, Cl, F, Br or CF.sub.3 ; provided when Z is CN or Cl, then when B is alkyl X-Y is not (VI) or (VII). Ferroelectric smectic liquid crystal mixtures containing these compounds are also described. ##STR1##

Chiral liquid crystal compounds

This invention relates to novel chiral cyano-containing compounds suitable for use in ferroelectric smectic liquid crystal mixtures.

A novel method of preparing thermochromic liquid crystal mixtures is provided in which mixtures which show an injected smectic phase at lower temperatures than their thermochromic cholesteric phase are prepared, and by following the envelope of the injected smectic - cholesteric transition on the phase diagram a series of thermochromic compositions containing the same components but having a series of working temperature ranges are obtained. Novel thermochromic liquid crystal mixtures prepared using the method are also provided.

Thermochromic liquid crystal materials and devices

Liquid crystal compositions are described which comprise a mixture of compounds and which includes at least one additive compound characterized in that the composition includes one or more additive compounds of Formula I as follows: ##STR1## wherein R.sub.1 represents an alkyl group, R.sub.2 represents an alkyl or alkoxy group or hydrogen and ##STR2## represents a 1,4-disubstituted bicyclo(2,2,2)octane ring. The preparation and properties of novel compounds of Formula I are also described. These liquid crystal compositions are useful in display devices such as digital calculators and word displays.

Liquid crystal materials containing substituted bicyclo(2,2,2)octanes

A liquid crystal material which comprises a mixture of compounds includes at least one low viscosity additive compound of Formula (I) as follows:

Liquid crystal materials

A liquid crystal guest-host display device includes a dye dissolved in the liquid crystal material. The invention is characterized in that the dye comprises three colored dye compounds mixed together to provide gray in the absence of an applied electric field. The compounds may be Sudan Black, Sudan Red and .beta.-carotene. The liquid crystal material preferably includes at least one 4'-alkyl- or -alkoxy-4'-cyanobiphenyl compound.

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Jennifer Constant