Dichroic azo dyes

A liquid crystal display comprising two substrates having disposed there between a guest-host composition comprising a liquid crystal host solvent and, as the guest, an arylazo or poly(arylazo) dichroic dye having at least one core radical selected from naphthyl or anthracyl and having at least one 2,3-dihydro-1,3-dialkyl perimidine substituent wherein the liquid crystal host solvent is a nematic or smectic liquid crystal and the dichroic dye has the general formula:

• Z--(X--N.sub.2).sub.n --A--N.sub.2 (--X--N.sub.2 --).sub.m --B
• wherein A is selected from the group consisting of a naphthyl radical (I), anthracyl radical (II) or anthracyl radical (III) and X is selected from the group consisting of a naphthyl radical (I), anthracyl radical (II), anthracyl radical (III) and phenyl radical (IV):
• ##STR14## wherein R.sup.1 and R.sup.2 are selected from the group consisting of --NO.sub.2, --CN, Br, Cl, F, --CO.sub.2 R.sup.3, --NR.sup.4 R.sup.5, --OR.sup.6 or R.sup.6 ;
• R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are selected from the group consisting of H and C.sub.1 to C.sub.10 alkyl groups;
• n and m are integers of 0 through 4;
• when n=0, Z is selected from the group consisting of --NO.sub.2, --CN, --CO.sub.2 R.sup.3, F, Cl, Br, R.sup.6, --OR.sup.6, --SO.sub.2, --CH.sub.3 SO.sub.2 --, CF.sub.3 SO.sub.2 --, C.sub.6 H.sub.5 SO.sub.2 --, --CF.sub.3, --C(O)CF.sub.3, 2,2-dicyanovinyl and 1,2,2-tricyanovinyl, and ##STR15## wherein R.sup.7 is selected from the group consisting of H and C.sub.1 to C.sub.10 alkyl groups, R.sup.8 and R.sup.9 are selected from the group consisting of H and C.sub.1 to C.sub.20 alkyl groups or form a C.sub.4 to C.sub.8 cycloaliphatic ring;
• when n is an integer of from 1 to 4, Z is as defined for z when n=0 or --NR.sup.4 R.sup.5 ;
• and B is ##STR16## wherein R.sup.10 is selected from the group consisting of C.sub.1 to C.sub.10 alkyl groups;
• R.sup.11 and R.sup.12 are selected from the group consisting of H and C.sub.1 to C.sub.20 alkyl groups or form a C.sub.4 to C.sub.8 cycloaliphatic ring.