Patent No. U.S. 7,169,223 B1
Merck Patent GmbH has obtained a patent for effect pigments having a color flop comprised of SiO2 flakes having a uniform layer thickness of 520 to 560 nm which are coated with one or more metal oxide layers, wherein the thickness of the one or more metal oxide layers is 15 to 40 nm, and wherein the color flop runs through all four quadrants of the a,b color coordinate system (CIELAB L,a,b system).