OPTICALLY EFFECTIVE SURFACE RELIEF MICROSTRUCTURES AND METHOD OF MAKING THEM

• Main Author: Stalder, Martin
• Format: Patent
• Language: English; French; German
• Published: 01.08.2018
• Subjects: BOOK COVERS; BOOKBINDING; CHECKING-DEVICES; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDEDFOR; FILES; HANDLING OF COINS OR OF PAPER CURRENCY OR SIMILAR VALUABLEPAPERS, e.g. TESTING, SORTING BY DENOMINATIONS, COUNTING,DISPENSING, CHANGING OR DEPOSITING; LOOSE LEAVES; MOVABLE-STRIP WRITING OR READING APPARATUS; OPTICAL ELEMENTS, SYSTEMS, OR APPARATUS; OPTICS; PERFORMING OPERATIONS; PHYSICS; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITYFEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOTOTHERWISE PROVIDED FOR; SPECIAL PRINTED MATTER; TRANSPORTING

The present invention relates to an element comprising a surface area with an anisotropic optically effective surface relief microstructure (12), which has a surface modulation of transitions from top regions (13) to bottom regions (14) and from bottom regions (14) to top (13) regions. The element is obtained by first generating a mask with a microstructure comprising first and second zones, wherein the microstructure of the mask has in a first lateral direction in average at least one transition from said first to said second zone or vice versa within every 20 micrometer and the lateral arrangement of the transitions is non-periodic in this direction. Due to anisotropic scattering, the surface relief microstructures of the elements of the invention are suitable to display images with a positive-negative image flip, which advantageously have a distinct and saturated color appearance but at the same time do not show any rainbow colors.