These inks have the particularity of being widely used in the fiduciary field. They are printed on most banknotes around the world to combat color photocopies. The very special pigments used only allow screen printing (see possibility in flexography and rotogravure after tests).
The best effect will be obtained with a thick layer of ink on the support and, to further optimize the result, an undercoat of black ink may be recommended with certain references. Conventional oxidative drying will give better results than UV drying. The color change of these inks will be optimized when the document is viewed from different viewing angles.
For example at 90°, the visible color will be red then by tilting the document, it will gradually change to gold, yellow then green.
Thanks to this phenomenon, it is extremely easy, without specific equipment, to distinguish an original from a copy.
Some references are specifically reserved for printing high security documents such as bank notes and passports but other references can be used for less sensitive documents.
