| abstract |
The invention concerns the use of indoline derivatives of the formula (I), in which R?1, R?2, R?3, R?4 and R?5, independently of each other, may be hydrogen atoms or alkyl groups with 1 to 4 C-atoms, or R?4 and R?5 together with the oxygen atoms to which they are bound may be an alkylenedioxy group with 1 to 4 C-atoms, or salts of such indoline derivatives, as additives to hair-dyeing agents of the direct-dyeing or developer/coupler type, thus producing hair dyeings with excellent colour-fastness characteristics. |