Patent ID: 7005507

Claim:
An azo dye of formula wherein R 1 is 2-trifluoromethyl-4-nitrophenyl, 2-cyano-4-nitrophenyl, 2-cyano-4-nitro-6-bromophenyl, 2-trifluoromethyl-4-chlorophenyl, 3,5-dicyano-4-methyl-2-thienyl or 2-cyano-4-nitro-1-naphthyl, R 2 is phenyl, benzyl or 2-phenylethyl and R 3 is phenyl, benzyl or 2-phenylethyl, with the proviso that either R 2 is phenyl and R 3 is benzyl or 2-phenylethyl or R 3 is phenyl and R 2 is benzyl or 2-phenylethyl.