Pearlescent silica flake pigments

Improved color strength and very high luster are produced by the combination of precise thickness silica flake substrate materials, selected for their interference chro-matidty, and by deposition of titania or iron oxide coating layers of the precise thickness required to generate the same interference color. These pearlescent pigments show stronger chromatidty L a b -values than can be produced with mica-based designs. 

Pearlescent Pigment on Mica Pearlescent Pigment on Silica Flakes... 

In practice, platelet crystals are synthesized with a layer thickness d calculated to produce the desired interference colors (iridescence). Most pearlescent pigments now consist of at least three layers of two materials with different refractive indices. Thin flakes (thickness ca. 500 nm) of a material with a low refractive index (mica, silica, alumina, glass) are coated with a highly refractive metal oxide (Ti 2, FejOj, layer thickness ca. 50-150 nm). This results in particles with four... 

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