Photochromic ink, also known as optical variable ink or chameleon ink, can present completely different colors under different viewing angles of human eyes in white light. It usually appears as a pair of colors, such as red-green, green-blue, gold-silver, etc. Its color-changing effect is strong, with large color difference and obvious features. Due to its color angle effect, it cannot be replicated by any high-definition scanner, color copier or other devices without any instruments, and its anti-counterfeiting reliability is extremely strong. The printing feature of photochromic ink cannot be imitated by any other ink and printing method.

The manufacturing process of photochromic ink generally involves dissolving photochromic colorants in solvents to produce micro-encapsulated pigments, and adding binders to the dissolved colorants for different purposes. Photochromic colorants can also be dissolved into monomers, and these polymer micro-particles can be pulverized and made into powders as pigments. Ink made with this method has ten times the light resistance compared to microcapsule ink. These powders can be added as pigments to water-based ink, oil-based ink, plastic ink and all adhesives. Photochromic ink is widely used in the anti-counterfeiting of currencies and securities in many countries due to its reliable anti-counterfeiting features.