Patent ID: 8083264

Claim:
A document, comprising: a paper substrate having an average surface roughness of at least about 0.5 microns, and selected from the group consisting of white paper that includes one or more optical brighteners and paper having a color other than white, wherein the paper substrate includes encoded information printed thereon, wherein the encoded information is printed with an ink comprised of light absorbing material that absorbs light only at wavelengths below 350 nm, and wherein the light absorbing material that absorbs light only at wavelengths below 350 nm is not colored and the ink is not fluorescent and does not emit any color when irradiated with light at wavelengths below 350 nm, and wherein the light absorbing material comprises nanoparticles having an average particle size of 300 nm or less selected from the group consisting of zinc oxide, silica, alumina, titania and mixtures thereof, or comprises an organic material selected from the group consisting of hydroxybenzophenones, hydroxybenzotriazoles, oxanilides, triazines, and mixtures thereof.