Display element based on the electroclinic effect

Claim 1

In an electroclinic effect display element containing a liquid crystal medium, the improvement wherein: said medium is a mixture of at least two chiral components and at least one non-chiral component, said medium has a compensated cholesteric phase above an optically active smectic A phase, wherein said medium is capable of exhibiting an electroclinic effect, and wherein said at least one non-chiral component is a compound of formula I ##STR12## wherein R 1 and R 2 are each independently an alkyl group with 5 to 15 C atoms wherein one or two non-adjacent CH 2 groups can also be replaced by --O--, --S--, --CO--O--, --O--CO-- and/or --CH═CH, ##STR13## is a 1,4-phenylene group optionally substituted by fluorine wherein in Formula I, at least one group ##STR14## is a 1,4-phenylene group which is substituted by fluorine, and n and m are each independently 1 or 2, and at least one of said chiral components is a compound of formula II ##STR15## wherein R 3 is an alkyl or alkenyl group each with 5 to 15 C atoms, optionally substituted by CN or at least one halogen atom wherein one or two non-adjacent CH 2 groups can be replaced by --O--, --CO--, --CO--O--, --O--CO--, --S-- and/or --C═C--, R 4 is an alkyl group with up to 8 C atoms wherein one CH 2 group can be replaced by --O--, --CO--O-- or --O--CO--, A 1 and A 2 are independently each an unsubstituted or mono- or polysubstituted 1,4-cyclohexylene group wherein one or two non-adjacent CH 2 groups may be replaced by --O--and/or --S--, a 1,4-bicyclo[2,2,2]octylene group, or a 1,4-phenylene group optionally substituted by fluorine, and wherein one or two CH groups may be replaced by N, X is CN, Cl, F, Br, CH 3 or CF 3 , Y is H or CH 3 , Z 1 is --CO--O--, --O--CO--, --CH 2 CH 2 --, --CHCN--CH 2 --, --CH 2 --CHCN--, --CH═CH--, --C═C--, --OCH 2 --, --CH 2 O--, --CH═N--, --N═CH--, --N═N--, --N═NO-- or a single bond, is 1, 2, or 3, and is an alkylene or alkenylene group with 1 to 7 C atoms wherein one CH 2 group can be replaced by --O--, --CO--O-- or --O--CO--, with the proviso that X, Y and R 4 are different groups.