Patent ID: 6686074
Filing Date: 2004-02-03
Classification: B41M,B42D,C09K,G07D,Y10S,Y10T

Abstract:
A secured document comprising a composition capable of anti-Stokes fluorescence comprising(a) a gadolinium oxysulfide selected from the group consisting of (1) a composition of the formula (Gd(1-x-y)YbxTmy)2O2S; and (2) a composition of the formula (Gd(1-x-y)2O2S:YbxTmy, wherein x and y are numbers greater than 0, wherein the wavelength of the emitted electromagnetic radiation is shorter than the wavelength of the absorbed electromagnetic radiation, and wherein the concentrations of Yb and Tm are adjusted to achieve concentration quenching of anti-Stokes luminescence.