Ciba-geigy Corporation

Ciba Specialty Chemicals Corporation

Werner Helmut Gerber

Abul Iqbal

Hanspeter Hauser

Pierre Maurer

In order to prevent or at least render difficult the copying of colored printed security papers, for example banknotes, the printing inks used for printing are so formulated that copies made using customary color copiers produce a markedly different color impression and can therefore easily be identified as being forgeries. This is achieved by using for the formulation of the printing inks dyes (pigments) that are as different as possible from the dyes (toners) customarily used in conventional color copiers. The choice of the dyes for the formulation of the printing inks is especially such that there is the greatest possible degree of metamerism between the printing ink in question and the match of the relevant master color using the dyes of the color copier. Preferably non-amorphous or anisotropic black dyes and effect dyes, especially fluorescent effect dyes, are co-used for the formulation of the printing inks.

Method of producing forgery-proof colored printed articles

A process and an apparatus for the preparation of color formula for the reproduction of the color of a master are described. In the process, during a measurement, the gloss component of the reflected light is already suppressed with polarizing filters, so that the calculation of the colorant concentrations may be carried out independently of the surface conditions of the master to be reproduced (glossy, semigloss, matte) with a set of optical data of the colorants that are independent of surface conditions.

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Riehen, Switzerland

Werner Helmut Gerber