Process for dyeing keratin materials using a direct dye and an aliphatic ammonium salt, and composition comprising same

A process for dyeing keratin fibers, comprising applying to the keratin fibers a direct dye composition comprising:

• a) at least one direct dye;
• and
• b) at least one tetra(C1-C8)alkylammonium salt of formula (A), optical, geometrical, or tautomeric isomers thereof, solvates thereof, or mixtures thereof:
• wherein in formula (A):
• R1, R2, R3, and R4, independently of each other, are chosen from a linear or branched, saturated or unsaturated (C1-C8) hydrocarbon-based groups, which may be optionally substituted with one or more radicals chosen from hydroxyl, amino, (di)(C1-C6)alkylamino, carboxy, carboxylate, carbamide, (C1-C4)alkoxy, —SO3H, sulfonate, and/or aryl;
• and
• Y− represents an anionic counterion;
• wherein when one of the hydrocarbon-based groups of R1, R2, R3, or R4 is substituted with a carboxylate or sulfonate group, Y− is absent to ensure the electrical neutrality of the at least one tetra(C1-C8)alkylammonium salt of formula (A);
• and
• wherein the tetra(C1-C8)alkylammonium salt is present in an amount ranging from 1% to 99.5% by weight, relative to the total weight of the composition,
• wherein the process does not comprise mixing the composition with an oxidizing composition.