Security element comprising micro- and macrostructures

#This application is a National Phase application of International Application No. PCT/EP2003/03482, filed on Apr. 3, 2003, which claims priority based on German Patent Application No. 102 16 562.9, filed on Apr 5, 2002, which are incorporated herein by reference.

#The invention relates to a security element.

#Such security elements comprise a thin layer composite of plastic material, wherein at least relief structures from the group consisting of diffraction structures, light-scattering structures and flat mirror surfaces are embedded into the layer composite. The security elements which are cut out of the thin layer composite are stuck on to articles for verifying the authenticity of the articles.

#Embodiments of the invention are described in greater detail hereinafter and illustrated in the drawing in which:

#FIG. 1 is a cross-sectional view of a security element,

#FIG. 2 shows a plan view of the security element,

#Referring to FIG. 1, reference 1 denotes a layer composite, 2 a security element, 3 a substrate, 4 a cover layer, 5 a shaping layer, 6 a protective layer, 7 an adhesive layer, 8 a reflecting interface, 9 an optically effective structure and 10 a transparent location in the reflecting interface 8. The layer composite 1 comprises a plurality of layer portions of various plastic layers which are applied successively to a carrier film (not shown here) and in the specified sequence typically comprises the cover layer 4, the shaping layer 5, the protective layer 6 and the adhesive layer 7. The cover layer 4 and the shaping layer 5 are transparent in relation to incident light 11. If the protective layer 6 and the adhesive layer 7 are also transparent, indicia (not shown here) which are applied to the surface of the substrate 3 can be perceived through the transparent location 10. In an embodiment the cover layer 4 itself serves as a carrier film while in another embodiment a carrier film serves for applying the thin layer composite 1 to the substrate 3 and is thereafter removed from the layer composite 1, as is described for example in above-mentioned GB 2 129 739 A.

#The common contact surface between the shaping layer 5 and the protective layer 6 is the interface 8. The optically effective structures 9 are shaped into the shaping layer 5 with a structure height HSt of an optically variable pattern. As the protective layer 6 fills the valleys of the optically effective structures 9, the interface 8 is of the same shape as the optically effective structures 9. In order to achieve a high level of effectiveness in respect of the optically effective structures 9 the interface 8 is provided with a metal coating, preferably comprising the elements from Table 5 of above-mentioned U.S. Pat. No. 4,856,857, in particular aluminum, silver, gold, copper, chromium, tantalum and so forth which as a reflection layer separates the shaping layer 5 and the protective layer 6. The electrical conductivity of the metal coating affords a high level of reflection capability in relation to visible incident light 11 at the interface 8. However, instead of the metal coating, one or more layers of one of the known transparent inorganic dielectrics which are listed for example in Tables 1 and 4 of above-mentioned U.S. Pat. No. 4,856,857 are also suitable, or the reflection layer has a multi-layer interference layer such as for example a double-layer metal-dielectric combination or a metal-dielectric-metal combination. In an embodiment the reflection layer is structured, that is to say it covers the interface 8 only partially and in predetermined zones of the interface 8.

#The layer composite 1 is produced as a plastic laminate in the form of a long film web with a plurality of mutually juxtaposed copies of the optically variable pattern. The security elements 2 are for example cut out of the film web and joined to a substrate 3 by means of the adhesive layer 7. The substrate 3 which is mostly in the form of a document, a banknote, a bank card, a pass or identity card or another important or valuable article is provided with the security element 2 in order to verify the authenticity of the article.