SECURITY DOCUMENT WITH A MAGNETIC FLUID

摘要

The invention relates to a security element comprising an optical image that can be modified by an external magnetic field. According to the invention, the security element (30) comprises a plurality of microcapsules (40) containing a suspension of a carrier liquid (42) and magnetic nanoparticles that reversibly form a photonic crystal (56, 58) in an external magnetic field of a magnet (60) in the microcapsules (40).