Base and Coupler
The oxidation dye pair is divided into Base and a Coupler. The condensed Base Coupler pair is coloured. This is because the electron clouds on the molecules effectively combines and gets delocalised in new molecular setup. The intense colour is the result of an intense interaction between light and a delocalised electron cloud.
The Base (ortho-or para-derivatives) yields the deep shades and becomes the basis of the colouring formulation. While the Couplers if taken separately yields colouring through oxidation that is only feeble.
- Aminophenols (amino naphthols)
- Phenols or naphthols
Oxidation dyes falls under two categories, namely oxidation base (primary intermediate) and coupler (secondary intermediate). For generating colour using these types, it is essential to use at least one type of each and mix it with a perfect oxidant under alkaline conditions. This would ensure the best results. Oxidation dyes often depends on a solution of dye intermediates like p-phenylenediamine for achieving the perfect colours. Another important ingredient is hydrogen peroxide. Typically a higher volume of peroxide in the dye has been seen to give a lighter and faster result.