Patent No. U.S. 6,517,627 B1
Nittetsu Mining Co., Ltd. and Katsuto Nakatsuka have obtained a patent for an additive pigment powder comprising three pigments, having the three primary colors of light (red, green, and blue), wherein each of the pigments is comprised of a base material having plural metal oxide films differing in refractive index and having a predetermined thickness based on Fresnel interference. The three primary colors of light reflect visible light only with a specified wavelength range and intensity corresponding to red, green or blue. Each of the pigments has a box-shaped spectral distribution in a specific wavelength range and a desired bright intermediate color can be developed by mixing these pigment particles in an appropriate proportion.