Abstract: A method is described for generating patterns representing a halftone image, said method comprising the generation of a first set of patterns consisting of lines and curves dimensionally modulated so as to produce variations in tones reproducing the halftones of the image using an intaglio rendering technique. The method comprises the generation of a second set of patterns consisting of microstructures separate from the lines and curves of the first set of patterns, said microstructures being dimensionally modulated so as to produce variations in tones reproducing the halftones of the image. According to a first aspect of the invention, the microstructures consist of stochastic microstructures that can be likened to a grain. According to a second aspect of the invention, the microstructures consist of repetitive microstructures reproducing information that can be recognized by an observer, which repetitive microstructures comprise microletters and/or microsymbols.

Abstract: There is described process for producing security papers, in particular banknotes, comprising the step of sealing the surface of the security papers by applying a protective pattern on the surface of the security paper, which sealing comprising printing the security papers by intaglio printing using an intaglio printing plate with engraved areas such that at least 80% of the whole surface of each security paper is covered with embossed intaglio patterns produced by engraved areas of the intaglio printing plate which are inked or with a combination of embossed intaglio patterns and flat intaglio patterns, which flat intaglio patterns are produced by unengraved areas of the intaglio printing plate which are inked after wiping of the intaglio printing plate, at least a part of the embossed intaglio patterns and/or flat intaglio patterns being printed with a transparent or semi-transparent intaglio ink.

Abstract: A method is described for generating patterns representing a halftone image, said method comprising the generation of a first set of patterns consisting of lines and curves dimensionally modulated so as to produce variations in tones reproducing the halftones of the image using an intaglio rendering technique. The method comprises the generation of a second set of patterns consisting of microstructures separate from the lines and curves of the first set of patterns, said microstructures being dimensionally modulated so as to produce variations in tones reproducing the halftones of the image. According to a first aspect of the invention, the microstructures consist of stochastic microstructures that can be likened to a grain. According to a second aspect of the invention, the microstructures consist of repetitive microstructures reproducing information that can be recognised by an observer, which repetitive microstructures comprise microletters and/or microsymbols.