Azo dye properties
Azo dyes give bright, high intensity colours, much more so than the next most common dye class (anthraquinones). They have fair to good fastness properties, but not so good as the carbonyl and phthalocyanine classes. Their biggest advantage it their cost-effectiveness, which is due to the processes involved in manufacture.
The general formula for making an azo dye requires two organic compounds- a coupling component and a diazo component. Since these can be altered considerably, an enormous range of possible dyes are available, especially as the starting molecules are readily available and cheap. Furthermore, the simplicity of the reactions mean that the process can be scaled up or down very easily, which is always a key factor in the cost of chemicals. Energy requirements for the reaction are low, since most of the chemistry occurs at or below room temperature. The environmental impact is reduced by the fact that all reactions are carried out in water, which is easy and cheap to obtain, clean and dispose of. As other dye classes become less viable from either an environmental or economic reasons, azo dyes become ever more attractive options.