Patent ID: 7083655

Claim:
Hair dye composition comprising at least one azo dye represented by the formula (1) A—N=N—B (1) where A is selected from the following groups (A-1) to (A-18) and (A-20) to (A-25) which are monovalent hetero-ring groups binding via symbol * to the azo group: wherein; R 21 to R 42 and R 45 to R 50 independently represent hydrogen atom, halogen atom, alkyl group, aryl group, hetero-ring group, cyano group, hydroxyl group, nitro group, alkoxy group, aryloxy group, amino group (including anilino group), acylamino group, aminocarbonylamino group, alkoxycarbonylamino group, alkylsulfonylamino group, arylsulfonylamino group, alkylthio group, arylthio group, hetero-ring thio group, sulfamoyl group, alkylsulfonyl group, arylsulfonyl group, acyl group, alkoxycarbonyl group, and carbamoyl group; or wherein, groups adjacent to each other as represented by R 21 to R 42 and R 45 to R 50 can bind together to form a saturated or unsaturated 5- or 6-membered ring structure, “a, p, q, r, s” represent an integer of 0 to 4, “b, c” represent an integer of 0 to 6, “d, e, f, g, t, u” represent an integer of 0 to 3, “h, i, j, k, l, o” represent an integer of 0 to 2, “m” represent an integer of 0 to 1, wherein 2 or more groups represented by R 21 to R 42 and R 45 to R 50 in the same molecule can be the same or different to each other, and wherein when R 21 to R 42 and R 45 to R 50 in the formulas (A-1) to (A-18) and (A-20) to (A-25) are groups with a possibility of additional substitution, R 21 to R 42 and R 45 to R 50 can further contain a substituent and the substituents are the same as listed as R 21 to R 42 and R 45 to R 50 and B=heterocyclic, aromatic or alkyl group containing a dissociative proton and, which is free of carboxy (—CO 2 H) or sulfo groups (—SO 3 H) or quaternary ammonium groups; and wherein a pKa of the dye is in the range of 1.5 to 9.0.