Method of dyeing hair characterised by use of an azo dye containing a dissociative proton

摘要

A hair dyeing composition contains a specific dissociative azo dye (1) free of sulfo, carboxyl and quaternary ammonium groups. A hair dyeing composition contains a dissociative azo dye of formula (1). A-N=N-B (1) A : optionally substituted phenyl or naphthyl; and B : atomic group containing dissociative proton. A and B are free of sulfo, carboxyl and quaternary ammonium groups. Independent claims are also included for the following: (1) dyeing human or animal hair which involves applying a composition containing azo dye of formula (1) to the hair, rinsing the hair after completion of dyeing and drying; and (2) usage of azo dye for dyeing human or animal hair.