Optical variable ink is the most complicated intervention-type anti-forgery ink. The printing products using this ink has colorful metal luster in which color lump shows a pair of colors, red-green, green-blue and golden-silver, for example. Seen from the front or lateral side under sunlight, the ink glows two different colors varying with the viewing angle, characterized by intense optical variation and sharp color changes, whose color angular effect cant be duplicated by high resolution scanner, color copying machine and other devices, and printing features can't be emulated by any other printing inks and printing types. With the unique design and special charm, it has become the rarely excellent anti-forgery ink and is recognizable without any devices. Furthermore, due to its complicated ink production process, huge investment, high anti-forgery reliability and involving high-technology in fields such as machinery, optics, electron, vacuum, superfine grinding, surface chemistry and high molecular material, it is applied in strictest and most difficult anti-forgery in currency and securities by many countries and in packing anti-forgery by some famous manufacturers.