Special effect pigments based on the layer-substrate principle belong to the group of high-performance pigments. These pigments, with their special luster and interference characteristics, are very important for the generation of new and unique effects when used in automotive and industrial paints, plastics, printing inks, and cosmetic formulations. Color effects such as pearl luster are produced by light reflection, interference, and absorption. Coloration of application systems with special effect pigments fulfills the highest aesthetic requirements. On the other hand, some of these pigments were developed especially for functional applications (bright electroconductive pigments, pigments for laser marking of polymers, and pigments with special spectral characteristics). Most of the special effect pigments consist of nanostructured, optical metal oxide layers coated on thin mica platelets. They are produced by a complex multiple step process including mica preparation, controlled deposition of transparent metal oxides with high refractive indices (titanium and iron oxide) and calcination. The color of the pigments is determined by the thickness of the metal oxide layers. Besides mica, newly developed substrate materials of silica and alumina flakes can be used for achieving innovative optical effects. Coated with metal oxides, these materials can be used for generating strong angle-dependent (optically variable coatings) and high chroma crystal effects. Deposition techniques for the deposition of special effect pigments include wet chemical deposition, web coating, crystal growth techniques, and the CVD process.
Optical coatings for special effect pigments
Optische Beschichtung für Spezialeffektpigmente
2004
5 Seiten, 4 Bilder, 2 Quellen
Aufsatz (Konferenz)
Englisch
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