US 2007/0183045 A1Published application

Diffractive security element comprising a half-tone picture

AssigneeOVD Kinegram AG

InventorsAndreas Schilling, Wayne Tompkin

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Abstract

A diffractive security element has a half-tone image comprising diffractive structures in a reflection layer, which are embedded in a layer composite between a transparent embossing layer and a protective lacquer layer. The half-tone image is divided into image elements of at least one dimension less than 1 mm, wherein the surface of each image element is divided up into a background field and an image element pattern. The proportion of the image element pattern to the surface of the image element determines the surface brightness of the half-tone image at the location of the image element. The background field has a first diffractive structure from which the image element pattern differs by its light-modifying effect. Pattern strips of a width of up to 0.3 mm additionally extend over the surface of the half-tone image. The pattern strips occupy a small proportion of the surface of the background fields and/or the image element patterns and produce coloured strips on the half-tone image.

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 surface structures, which is embedded between the embossing layer and the protective lacquer layer, wherein the surface portions with the first surface structures form background fields and the surface portions with the surface structure which differs from the first 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 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.

Abstract

Claims17