| abstract |
The invention provides carboxylate compounds of the following formula (A):n n wherein R is a group selected from C₃-C₂₀ alkyl, C₃-C₂₀ alkoxy and halogenated C₃-C₂₀ alkyl, X and Y are each, independently, a group selected from: -COO-,-OCO-, -CH₂CH₂-. CH₂O-, OCH₂-, -S-S-,n n andn n or a single bond, A and B are each, independently, a group selected fromn n andn n and R * is an optically active group of 4 to 20 carbon atoms, the group containing at least one asymmetric carbon atom and being optionally substituted by one or more halogen atoms, and m and n are each an integer of 0 to 2; with the proviso that both m and n are not 0 at the same time. n The compounds are employed in liquid crystal compositions. A liquid crystal element containing such a composition, a process for the preparation of the element and a method of light modulation involving use of the element are also disclosed. |