US Patent 7238424 All-dielectric optically variable pigments

The light transmitted and reflected by all-dielectric optically variable pigments varies according to viewing angle. The color travel of an all-dielectric optically variable pigment depends on amplitude changes and wavelength shifts in reflectance peaks of the pigment. The width and center wavelength of reflectance peaks can be controlled by selecting the ratio of thicknesses between high-index and low-index layers in a thin film stack. Reflectance peaks can regenerate or become suppressed and shift with tilt angle, thus providing a wide variety of color trajectories.