Security element with subwavelength diffraction grating

摘要

The present invention relates to a security element for producing valuable documents such as banknotes, checks and the like. This comprises a dielectric substrate (1) and a plurality of first gratings having a first grating gap (4) extending in the longitudinal direction and arranged in a first plane (L1) and positioned between them. A first periodic linear lattice structure (2) consisting of a web (3) embedded in a substrate (1) and a second lattice gap (8) extending longitudinally and positioned between them And a second linear lattice structure (6) of the same period (d) embedded in the substrate (1), comprising a second lattice web (7). The second linear lattice structure (6) is positioned above the first linear lattice structure (2) in the second plane (L2) parallel to the first plane (L1). The two linear lattice structures (6) are formed in an inverted state with respect to the first linear lattice structure (2). Thereby, in the plan view of the first plane (L1), the second lattice web (7) is above the first lattice gap (4) and the second lattice gap (8) is It is on the lattice web (3). The security element (S) generates a color effect when looking at the transmission (T), and the lattice web (3) of the first linear lattice structure (2) and the second linear lattice structure (6) Each of the lattice webs (7) is formed of a double layer composed of a layer of high refractive index material (3a, 7a) and a layer of metal material (3b, 7b).