INFORMATION CARD Russian patent published in 1998 - IPC

FIELD: protection of securities, certificates, credit, check and other information cards against copying and forgery. SUBSTANCE: information card has backing and microrelief made in the form of diffraction grating with triangular or trapezoidal profiles of slits. Inclination angle of their side changes periodically along surface of backing in direction of alternation of slits. Spacing of diffraction grating lies within range 04.-10.0 μ and changes with same period as that of change of inclination angle of side of slits. Period of change of inclination angle of sides lies within range 0.25-100.0 mm and range of inclination angle of sides amounts to not less than two degrees. Microrelief may be made both on backing and on metallized light reflecting layer and covered by transparent layer. Scattering of directed white light by microrelief makes it possible to view dark, light and color iridescent stripes periodically repeating on surface of information card. EFFECT: improved efficiency of protection. 3 cl, 2 dwg