Ultra-violet fluorescent ink is a special printing one giving off visible light (400-800nm) while exposed to ultraviolet light (200-400nm). Ultraviolet light is divided into short wave and long wave according to the excitation wave length. The ink of an excitation wave length of 254nm is called shortwave ultra-violet fluorescent ink and that of 365nm is long wave ultra-violet fluorescent ink. It is divided into three kinds by colors: Achromatic, chromatic and discoloration. Achromatic ink can glows red, yellow, green and blue colors; chromatic ink can brighten the original color; discoloration ink can change from one color to another, which is applied in printing RMB notes, bank books and taxation invoices.