Introduce

Pearlescent effect pigments consist of a substrate having a laminar (layered) structure of high aspect ratio (surface

dimension/thickness). The interference colors are derived from coating TiO2 onto these high aspect ratio substrates in very specific thicknesses. Due to the difference in refractive index (speed of light through a medium) between

the oxide and substate layer, incoming wavelengths of white light, hitting the coated flakes, are separated into very specific reflection and transmission components. For example, a thin layer of TiO2 results in a white “pearlescent” effect, whereas a thick layer of TiO2 results in a green reflection component with a corresponding red transmission component or “iridescent” effect. By fine tuning the thickness of TiO2 all colors of the spectrum are possible. As the light continues to pass through the film it is further reflected off nearby flakes in a similar manner, which when seen by an observer, gives a sense of depth to the formulation in which they are used.

In a similar manner, varying thicknesses of Fe2O3 by itself, or in combination with TiO2, result in non-metallic metallic effects with a “pearlescent luster”. However, due to the absorption color component of Fe2O3 an observer perceives a “metallic” luster instead. Thin layers of Fe2O3 result in shades of gold and as they become thicker progress through bronze, copper, and russet color effects. In addition, various colors can be imparted by using various colorants (organic pigments/inorganic pigments, etc.).