The present invention relates to novel direct dyes and compositions comprising them for dyeing keratin fibers especially human hair. The novel dyes of the present invention have benzothiophene structure providing intensive and homogeneous dyeing on keratin fibers, especially human hair.

Disclosed is 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.

Provided are an azo dye composition including an azo dye compound represented by Formula (I) and a urea compound represented by Formula (II), and a method for producing an azo dye composition. R.sup.11, R.sup.12, R.sup.13 and R.sup.14 each independently represent a hydrogen atom, a halogen atom, or an aliphatic group; R.sup.15 represents an aliphatic group; R.sup.21 and R.sup.22 each independently represent a hydrogen atom, an aliphatic group, or an aromatic group; and n represents an integer from 0 to 2. ##STR00001##

A hair dye composition comprising the following components (A) and (B), in which the mass ratio of the component (B) to the component (A), (B)/(A), in a whole composition is 1 or more and 100 or less and the pH (25 C.) during application is 7.5 to 12: (A): one or more azo dyes selected from the group consisting of the following (A-1), (A-2) and (A-3)

##STR00001## (B): 2-amino-2-methylpropanol.

Provided are an azo dye composition including an azo dye compound represented by Formula (I) and a urea compound represented by Formula (II), and a method for producing an azo dye composition. R.sup.11, R.sup.12, R.sup.13 and R.sup.14 each independently represent a hydrogen atom, a halogen atom, or an aliphatic group; R.sup.15 represents an aliphatic group; R.sup.21 and R.sup.22 each independently represent a hydrogen atom, an aliphatic group, or an aromatic group; and n represents an integer from 0 to 2.

##STR00001##

The present disclosure provides a compound represented by the following formula (1).

##STR00001##

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.