Method and device for embossing planar material

Abstract

A method for embossing a first grating in a planar material, by means of an embossing body and a counter embossing body, having each a hard surface, the first grating to be embossed comprising alternating substantially parallel and straight ridges and recesses, whereby the top surfaces of the ridges are intended to weaken a direct angular reflection of light by diffuse omnidirectional reflection, thereby producing a visible contrast between the ridges and the recesses. The method comprises on the embossing body providing a first plurality of obtuse pyramids intended to emboss the recesses of the first grating by exerting pressure on a first side of the planar material, the first plurality of obtuse pyramids forming first intermitted lines (row1, row2) corresponding to the intended recesses, and the pyramids in each subset corresponding to one of the first intermitted lines, being separated from each other by a determined distance that creates a gap in the line in such a manner that each gap from a line of pyramids may be connected to a corresponding gap from an adjacent line of pyramids by an imaginary line perpendicular to both of the adjacent lines; and roughening portions of the hard surface of the embossing body, the portions being located between adjacent lines of pyramids and intersecting at least one of the imaginary lines that connect one gap from one line to the corresponding gap from the adjacent line. On the counter embossing body, the method comprises providing a second plurality of obtuse pyramids intended to emboss the ridges of the first grating by exerting pressure on a second side of the planar material opposite to the first side, during embossing the obtuse summits of the pyramid pressing the planar material against a roughened portion of the hard surface of the embossing body, thereby satirizing the top surfaces of the ridges on the first side.