Patent ID: 10882352

Abstract:
A method for embossing optically diffracting microstructures in a thin foil, such as used to pack at least one of the list comprising food, chocolate, chewing gum, gifts, jewellery, clothes, tobacco products, pharmaceutical products, the embossing being produced with an embossing rollers set-up comprising at least one cylindrical embossing roller and a cambered counter roller. The method comprises confining the at least one cylindrical embossing roller and the cambered counter roller in a single roller stand of relatively small outer dimensions designed to withstand a pressure for the at least one cylindrical embossing roller and the cambered counter roller; using on a surface of a first one of the at least one cylindrical embossing rollers at least one raised embossing element adapted for microstructure embossing, whereby one of the at least one raised embossing elements comprises a platform distant at a height in a range between 5 m and 30 m above a surrounding surface of the first cylindrical embossing roller adjacent to it, and a pattern engraved on top of the platform (5), whereby the pattern comprises the optically diffracting microstructures with periodicity of gratings in the range smaller than 30 μm that produce from a diffuse or directed source of light in the visible wavelength range diffraction images with high contrast and high luminosity in a defined observation angle; and adjusting the pressure for the at least one cylindrical embossing roller on the thin foil in a range less than 80 bar relative to a platform area of approximately 100 mm2.