Patent ID: 7719733

Claim:
A diffractive security element with a half-tone image comprising surface portions occupied with microscopically fine surface structures enclosed in a layer composite which includes at least a transparent embossing layer, a protective lacquer layer and a reflection layer with the microscopically fine surface structures, which is embedded between the embossing layer and the protective lacquer layer, wherein the surface portions with the first microscopically fine surface structures form background fields and surface portions with a second microscopically fine surface structure which differs from the first microscopically fine surface structures in at least one structural parameter form image element patterns and the surface of the half-tone image is divided into a plurality of image elements which are composed of the surface portions of the image element pattern and the background field and which are smaller than 1 mm at least in one dimension, wherein the image element patterns in the image elements are of the same size, pattern strips extend with a line pattern of a width of 15 μm to 300 μm at least over a part of the surface of the half-tone image and partially cover the background fields and image element patterns, the line pattern is formed from surface strips with pattern structures and with line widths in the range of 5 μm to 50 μm, wherein the line patterns include letters, texts, line elements and pictograms and the pattern structures differ from the first and second microscopically fine surface structures in at least one structural parameter, the line width of the surface strips in the background fields is constant and the surface brightness of the image elements is controlled by means of the line width of the surface strips on the image element pattern in such a way that the surface proportion of the image element pattern not covered by the line pattern is determined in accordance with the surface brightness of the image original of the half-tone image at the location of the image element and having regard to the surface brightness of the adjacent image elements, wherein the spatial frequency of linear diffraction gratings in the pattern structures is selected from the range of 800 lines/mm to 2000 lines/mm.