Liquid crystal coupled dichroic dyes

A liquid crystal coupled dichroic dye composition comprising a dichroic dye moiety coupled to one or two nematogenic or smectogenic liquid crystal moieties by a flexible spacer group having at least four atoms linked in a linear fashion wherein the liquid crystal coupled dichroic dye composition has the general formulae:

• A--X--Y--Z--B (I)
• or
• B--Z--Y--X--A--X--Y--Z--B (II)
• wherein A is a nonionic dichroic dye moiety such that the liquid crystal coupled dichroic dye has an absorption maximum between 400 and 2000 nm and an extinction coefficient of greater than 2,000;
• X and Z are independently:
• ##STR14## or a covalent bond linkage, wherein R.sub.1 is hydrogen, a methyl group, or an ethyl group;
• Y is a linear or branched C.sub.2 to C.sub.12 alkyl group which is uninterrupted or interrupted by one or more of --O--, --S-- or --NR.sub.1 --;
• B is a liquid crystal moiety having the general formula:
• --D--W--D--R.sub.2, (III)
• --D--W--D--D--R.sub.2, or (IV)
• --D--D--W--D--R.sub.2 (V)
• wherein D is a 1,4-disubstituted benzene ring, a 1,4-disubstituted cyclohexane ring, or a 2,5-disubstituted pyrimidine ring, W is ##STR15## or a covalent bond linkage, provided that W is not a covalent bond linkage when B comprises three rings, R.sub.2 is a C.sub.1 to C.sub.12 alkyl group, C.sub.5 to C.sub.7 cycloalkyl group, C.sub.1 to C.sub.12 alkoxy group, C.sub.1 to C.sub.12 alkoxycarbonyl group, nitrile group, nitro group or NR.sub.3 R.sub.4 wherein R.sub.3 and R.sub.4 are hydrogen or C.sub.1 to C.sub.12 alkyl groups;
• and X--Y--Z comprises at least four linearly linked atoms.