Illuminated fountains

Abstract

Hard nitrides of group IVb metals can display not only gold-yellow, but also other fashionable colors as bronze, brown, violet, dark-blue and almost black by small variations of their stoichiometrical composition. The interest in this type of coatings for millinery goods such as watch cases, bracelets, lighters, jewels etc., is growing. The exact reproduction of tints remains delicate because of the extreme sensitivity of the human eye for small color differences. This fact limits the number of deposition methods available for decorative purposes to those where precise control of deposition parameters is possible. After a short review of the historical development of these coatings, their optical properties and other quality requirements, factors influencing color and various possibilities of process monitoring in reactive plasma-assisted physical deposition methods are discussed.