A method for dyeing keratin fibers, wherein a composition is applied to said fibers which contains, in a suitable dyeing medium, at least one coupler having formula (I) ##STR1## wherein R.sub.1 is hydrogen or alkyl; R.sub.2 and R.sub.3 are hydrogen, alkyl, COOR', where R' is alkyl or hydrogen; R.sub.4 is hydrogen, hydroxyalkyl, alkyl, polyhydroxyalkyl or acetyl or aminoalkyl wherein the amine may be mono- or disubstituted by alkyl; Z.sub.1 and Z.sub.2 are hydrogen, alkyl, hydroxy, halogen, alkoxy or a salt thereof; at least one precursor of an oxidation hair dye; and at least one oxidizing agent, the pH of the composition applied to the fibers being less than 7.
一种染色角蛋白纤维的方法,其中将含有至少一种具有以下式(I)的
偶联剂的组合物施加到所述纤维中,其中R.sub.1为氢或烷基;R.sub.2和R.sub.3为氢、烷基、COOR',其中R'为烷基或氢;R.sub.4为氢、羟基烷基、烷基、多羟基烷基或乙酰基或
氨基烷基,其中胺基可以被烷基单取代或双取代;Z.sub.1和Z.sub.2为氢、烷基、羟基、卤素、烷氧基或其盐;至少一种氧化染发剂的前体;和至少一种氧化剂,施加到纤维上的组合物的pH值小于7。