Patent No. U.S. 6,521,036 B1
SICPA has obtained a patent for optically variable pigments having a color shift between two distinct predetermined colors. The optically variable pigment is comprised of a multilayer thin-film interference stack having first and second substantially parallel planar surfaces. The multilayer stack includes an opaque reflecting layer having first and second substantially planar surfaces that are parallel to the first and second parallel planar surfaces of the multilayer stack and at least one sequence disposed on one of the first and second surfaces of the opaque reflecting layer. Each sequence is comprised of a dielectric layer with an index of refraction of 1.65 or less and a semi-transparent partially reflecting layer with the dielectric layer of said sequence being first disposed on the totally reflecting layer, wherein the totally reflecting layer is made of a corrosion-resistant aluminum alloy by physical vapor deposition.