Patent ID: 7102823

Claim:
A diffractive security element having an optical waveguide comprising a transparent dielectric integrated into a layer composite and embedded between a transparent base layer to be illuminated and a protective layer, wherein the dielectric differs in refractive index from the plastic material of the adjoining layers and in surface portions bears closely against an optically effective structure of an interface in relation to the base layer, and wherein in the waveguide the transparent dielectric is of uniform layer thickness (s) and is of a value of the refractive index of at least 2, the waveguide is modulated by means of the optically effective structures and the optically effective structure as a base structure has a zero order diffraction grating with a diffraction grating vector, a period length (d) from the range of between 100 and 500 nm and a profile depth (t) from the range of between 20 nm and 1 μm, the waveguide is of a minimum length (L) of at least between 10 and 20 period lengths (d) of the zero order diffraction grating, and in at least one of the surface portions, the profile depth (t) and the layer thickness (s) for modulation of the waveguide are in a predetermined ratio of either t≈3s, s≈t or s≈2t.