Mainly used for polyester. They are nonionic in nature. These dyes are characterized by their high degree of dispersion and especially suitable for dyeing and printing of polyester in various form either alone or as a mixture with other fibers.

Naphthol dyes are insoluble azo dyestuffs that are produced on the fibre by applying a Naphthol to the fibre and then combining it with a diazotized base or salt at low temperature. Azoic combinations are still the only class of dye that can produce very deep orange, red, scarlet and Bordeaux shades of excellent light and washing fastness.