Organic pigments are insoluble organic matter, usually added to the substrate in a highly dispersed state to color the substrate. The fundamental difference between them and dyes is that dyes can be dissolved in the dyeing medium used, while pigments are neither soluble in the medium in which they are used nor in the substrate to be colored.
Many pigments and dyes are consistent in chemical structure, and different methods of use can make them convert into each other. For example, some vat dyes and sulphurized vat dyes can be used as fiber dyes if they are reduced to leuco bodies; if they are not reduced, they can be used as pigments for high-grade inks.
Organic pigments are widely used in inks, paints, coatings, raw pulp coloring of synthetic fibers, as well as fabric coating printing, plastics, rubber, and leather coloring, among which the largest amount of pigments are used in inks. The output of organic pigments accounts for about a quarter of the total output of dyes.
There are two types of dyes made from organic compounds: natural and artificial, such as indigo and Haichang blue. Corresponding to them are inorganic dyes, such as mineral dyes.
Pure natural organic dyes are mainly plant dyes. According to the chemical composition, it can be divided into seven types: carotenoids, anthraquinones, naphthoquinones, flavonoids, curcumin, indigo, and chlorophyll.
