Patent ID: 7238424

Claim:
A dichroic pigment flake comprising: a plurality of thin film layers forming an optical interference structure with a m th -order reflectivity peak, where m is an integer greater than 1, the m th -order reflectivity peak having a first reflectivity at a first viewing angle and a second reflectivity at a second viewing angle, the first reflectivity and the second reflectivity being expressed as a percentage of total reflectivity, wherein the first reflectivity is less than the second reflectivity by at least 20%, wherein the plurality of thin-film layers are arranged as (aH bL) n aH wherein n is an integer and a and b are multipliers, H representing thin-film layers of high-index material having a relative index of refraction not less than 2.0 and a quarter-wave optical thickness at a center wavelength λ400 nm to 2200 nm, and L representing thin-film layers of low-index material having a relative index of refraction not greater than 1.6 and the quarter-wave optical thickness at the wavelength, and wherein a ratio a:b is an integer ratio between 1:4 and 4:1.