Changing the shape and color of hair is an important field of modern cosmetics. The appearance of the hair can thus be adapted both to current trends and to the individual desire of the individual consumer. Consumers turn to color-changing agents for the fashionable coloring of hairstyles or to cover grey or even white hair with fashionable or natural color shades. In addition to a high coloring performance, these agents should have additional properties, such as increasing the volume of the hair.
Various coloring systems are known in the prior art in order to provide color-changing cosmetic agents, in particular for the skin or for keratin-containing fibers, such as human hair.
Oxidation dyes are used for permanent intense colorings having appropriate fastness properties. Such dyes usually include oxidation dye precursors, or what are known as developer components and coupler components. The developer components form the actual dyes under the influence of oxidizing agents or atmospheric oxygen with one another or with coupling to one or more coupler components. The oxidation dyes are indeed characterized by excellent, long-lasting color results. However, for naturally acting dyes, a mixture of a larger number of oxidation dye precursors has to be used; in many cases direct dyes are also used for providing color variations.
Dyes or toners which include what are known as direct dyes as coloring component are usually used for temporary colorings. Direct dyes are dye molecules which are drawn directly onto the substrate and do not require an oxidative process in order to form the color. These dyes include, for example, henna, which is already known from ancient times for coloring the body and hair. These dyes are generally much more sensitive to shampooing than oxidative dyes, and therefore a change in color or a visible loss of homogenous color, which is undesirable for many reasons, occurs much earlier.
Lastly, a further coloring method has drawn much attention. In this method, precursors of the natural hair colorant melanin are applied to the substrate, for example hair; these then form dyes similar to natural dyes within the scope of oxidative processes in the hair. In such a method, 5,6-dihydroxyindolin for example is used as dye precursor. In particular, with multiple application of agents comprising 5,6-dihydroxyindolin, it is possible to reinstate the natural hair color in individuals that have grey hair. The coloration can be provided here with atmospheric oxygen as sole oxidizing agent, such that it is possible to dispense with further oxidizing agents. In individuals having originally medium-blond to brown hair, 5,6-dihydroxyindolin can be used as the sole dye precursor. For use in individuals having originally red and in particular dark to black hair color, satisfactory results can be attained by contrast often only by co-use of further dye components, in particular specific oxidation dye precursors.
The dyes known in the prior art, however, do not always lead to the desired high coloring performance, in particular lightening performance, or have additional desired properties, such as improved care of the hair during the hair-coloring process.