Liquid crystal-base composition for an electro-optical device

A liquid crystal guest-host composition containing a liquid crystalline host and a guest pleochroic colouring agent for use in an electro-optical device, wherein said colouring agent is an anthraquinone compound represented by the general formula (I):

• ##STR14## in which R.sub.1 is an amino group which can be alkylated or acylated, an alkoxy group or a hydroxy group;
• R.sub.2, R.sub.3 and R.sub.4 which are identical or different are each a hydrogen atom, an amino group which can be alkylated or acylated, a substituted or unsubstituted an alkoxy group, a hydroxy group, a nitro group, a halogen atom or a cyano group;
• A is selected from the group consisting of ##STR15## in which X is a hydrogen atom, a halogen atom, a mercaptan group, a cyano group, a cyclic, branched or straight alkyl chain, an alkoxyalkyl chain, a hydroxyalkyl chain, a pyridyl group, a benzyl group, a phenyl group, a para-alkylphenylene group, a para-alkoxyphenylene group, a para-cyanophenylene group, with at most 10 C atoms, or a group selected from OR', SR', OOCR', OOC--C.sub.6 H.sub.4 --R', SOC--C.sub.6 H.sub.4 --R', NHR', NHCOR', OCOOR' and OCOO--C.sub.6 H.sub.4 --R', in which R' is a hydrogen atom, a cyclic, branched or straight alkyl chain, an ethoxycarbonylalkyl chain, a cyanoalkyl chain or a phenyl group, with at most 10 C atoms, and n is an integer of from 3 to 7, and Y is a hydrogen atom or a side chain having the same definition as A.