These inks have become very popular and are now used on most high security documents like passports and bank notes around the world.
They are made with very special pigments which allow a color change (or a flip-flop effect) when the document is tilted.
In fact these inks are almost transparent when viewed at 90° but become colorful when viewed at a 45° angle.
They are very useful to combat photocopies and scanners because their appearance completely changes on the copy.
A large number of shades are available for flexography, screen printing and rotogravure (either in aqueous version, or solvent based, or UV drying) but due to the size of the pigments, offset and letterpress printing is impossible .
For Flexography, you must use an anilox which allows a significant ink deposit (minimum 15 to 20 cm3/M²)
