This family of inks showing a change of colours according to the angle of view is widely used in fiduciary fields and is used on many banknotes in the world, in order to avoid colour photocopies.
Our RVI inks (Reflexion Variable inks) use very special pigments, and printing process used with those inks are silk-screen, flexography and gravure. Offset cannot be used.
The best effect will be obtained with a rather thick deposit of ink on the support, and with some references of RVI inks it is advisable to underprint a black ink. Hot-air drying and UV drying formulations can be used, but hot air drying will give best results regarding the change of colours according tio the angle of view. For example, at 90° the colour of the print will be visible red, then when varying the angle of view, the colour will pass to gold, then yellow, and green.
Due to this phenomenon, it is very easy, without any specific material, to distinguish an original from a photocopy. Some references are specifically reserved for high security documents, such as passports, Identity documents, visas, banknotes, but other references can be used on less sensible documents.