Patent ID: 7189268

Claim:
A method of dyeing fibres of living human hair, which comprises contacting the fibres with a dye of the formula wherein R 1 and R 2 are each independently of the other hydrogen, C 1 –C 4 alkyl, halogen or nitro, R 3 and R 4 are each independently of the other unsubstituted C 1 –C 4 alkyl or C 1 –C 4 alkyl substituted by OH, C 1 –C 4 alkoxy, halogen, CN or by phenyl, X 1 and X 2 are each independently of the other hydrogen, C 1 –C 4 alkyl, C 1 –C 4 alkoxy or halogen, R 5 is hydrogen or C 1 –C 4 alkyl, R 6 is C 5 –C 8 cycloalkyl each unsubstituted or substituted by OH, C 1 –C 4 alkoxy, halogen, CN or phenyl, or R 6 is C 1 –C 4 alkyl substituted by phenyl or by C 5 –C 8 cycloalkyl, or wherein R 5 and R 6 together with the nitrogen atom linking them form a piperazine ring, which is substituted, at the nitrogen atom that is not bonded to the phenyl group, by phenyl, or which is quaternised at that nitrogen atom by two penyl groups, the phenyl mentioned as substituents of the nitrogen atom of the piperazine ring being unsubstituted or substituted by OH, C 1 –C 4 alkoxy, halogen, CN or phenyl, and wherein X − is an anion.