Method and device for embossing relief structures

A method of embossing individually light-reflecting areas on a foil material by a pair of rollers including a first roller and a second roller, the first roller and second roller having, at respective surfaces at least in a perimeter, a plurality of polyhedron-shaped positive projections and a plurality of negative projections complementary to the positive projections, the perimeter having at least one positive projection, the plurality of positive projections are arranged according to a two-dimensional grid, each one of the plurality of positive projections extending over an individual height from a base side of the positive projection at the surface of the first roller to a top side of the positive projection in a direction away from a rotation axis of the first roller, and each negative projection extending from the surface of the second roller to a bottom side of the negative projection in a direction towards the rotation axis of the second roller, the plurality of polyhedron-shaped positive projections joining with corresponding negative projections at an embossing location of the foil material, enabling a homogeneously jointed embossed polyhedron-like shape in the foil, the method comprising:

• feeding a foil material into a roller nip between the pair of rollers;
• adjusting an orientation and a shape of each of the positive projections, in the two-dimensional grid;
• and
• embossing the foil material to provide a plurality of light-reflecting areas on the foil material, the light reflecting areas configured to reflect light in line with a table of reflectivity values for the two-dimensional grid, according to an orientation and shape of each of the plurality of light-reflecting areas for which the orientation and the shape of a corresponding positive projection is adjusted, to thereby enable a perception of the reflected light on a wide viewing angle covered by reflected light from the light-reflecting areas,
• wherein at least one positive projection of the plurality of polyhedron-shaped positive projections comprises a height and/or tilting angle with respect to a planar surface tangent to the surface of the first roller at the center of the base area of the positive projection, which differs from the height and/or tilting angle of at least one of the other positive projections of the plurality of polyhedron-shaped positive projections, and the plurality of negative projections complementary in depth and/or tilting angle to the plurality of positive projections.