In the era of banknote payments, producing high-quality banknotes is difficult, and the most challenging part is anti-counterfeiting. Nowadays, the most advanced anti-counterfeiting technology is optically variable ink, which has strong color-changing properties, a significant color difference, and distinctive characteristics. It can be recognized without using any instruments, and it cannot be replicated using other devices. So far, it has not been successfully counterfeited and is widely used in various banknote printing.

Optically variable ink is also known as optical variable ink and color-shifting ink. The manufacturing method of this ink is mainly to dissolve the photochromic color and then use colorants to make pigment capsules, which are added with adhesives for different uses. The color blocks on the printed matter usually present two colors that are relative to each other, such as red vs. green, green vs. blue, gold vs. silver, etc. These characteristics facilitate the identification of the authenticity of banknotes. Another higher manufacturing method is to dissolve the optically variable ink into a polymer monomer through professional techniques, break its polymerization state chemically, and then make it into a powder for use as a pigment. This manufacturing method increases the light resistance of the ink by ten times compared to ordinary ink.