Provided is a composition containing a compound of formula (1), and a polymerizable liquid crystal compound or a liquid crystalline polymer compound. n represents 1 or 2; Ar.sup.1, Ar.sup.2, and Ar.sup.3 each represent a 1,4-phenylene group or a divalent sulfur-containing aromatic heterocyclic group; At least one of Art and Ar.sup.2 has a fluorine atom; R.sup.1 represents a single bond or a group selected from —OC(═O)—, —C(═O)O—, —C≡C—, —CH═CH—, —CH═N—, —N═N—, and —N═CH—; R.sup.2 represents an alkylamino group or an alkoxy group; R.sup.3 represents a group selected from an alkanediyl group, an alkanediyloxy group, an alkanediyloxycarbonyl group, and an alkanediylcarbonyloxy group; and R.sup.4 represents a polymerizable group or a hydrogen atom.

R.sup.4—R.sup.3—Ar.sup.1—(—R.sup.1—Ar.sup.2—).sub.n—N═N—Ar—R.sup.2   (1)

Disclosed is an azo compound represented by Formula (I)

##STR00001##

in which R.sup.1 is hydrogen or methyl, R.sup.2 is hydrogen or methyl, and R.sup.3 is hydrogen, an unsubstituted linear alkyl group of from 1 to 4 carbon atoms, or an unsubstituted branched alkyl group of from 1 to 9 carbon atoms. This disclosure also provides a black dye composition including the azo compound represented by Formula (I).

Disclosed is an azo compound represented by Formula (I), ##STR00001##
in which R.sup.1 is hydrogen or methyl, R.sup.2 is hydrogen or methyl, and R.sup.3 is hydrogen, an unsubstituted linear alkyl group of from 1 to 4 carbon atoms, or an unsubstituted branched alkyl group of from 1 to 4 carbon atoms. This disclosure also provides a black dye composition including the azo compound represented by Formula (I).

A composition contains a compound of formula (1), and a polymerizable liquid crystal compound or a liquid crystalline polymer compound. n represents 1 or 2; Ar.sup.1, Ar.sup.2, and Ar.sup.3 each represent a 1,4-phenylene group or a divalent sulfur-containing aromatic heterocyclic group; At least one of Ar.sup.1 and Ar.sup.2 has a fluorine atom; R.sup.1 represents a single bond or a group selected from OC(?O), C(?O)O, C?C, CH?CH, CH?N, N?N, and N?CH; R.sup.2 represents an alkylamino group or an alkoxy group; R.sup.3 represents a group selected from an alkanediyl group, an alkanediyloxy group, an alkanediyloxycarbonyl group, and an alkanediylcarbonyloxy group; and R.sup.4 represents a polymerizable group or a hydrogen atom.
R.sup.4R.sup.3Ar.sup.1(R.sup.1Ar.sup.2).sub.nN?NAr.sup.3R.sup.2(1)

A mono-azo dichroic dye compound represented by the following Chemical Formula 1, a composition for polarizing plate, a polarizing plate, and an optical device. ##STR00001## In Chemical Formula 1, Z represents any one selected from the group consisting of CN, COOR.sub.11, indanone and 1,3-dioxoindane, wherein R.sub.11 is any one selected from the group consisting of alkyl groups, aryl groups, and substituted or non-substituted heteroaryl groups. The mono-azo dichroic dye compound shows excellent dichroic properties, and has excellent heat resistance and photo-resistance, and thus may be used advantageously for a dye-based polarizing plate.