Optically variable inks were first used in the anti-counterfeiting printing of banknotes, checks, bonds and other securities. With the continuous development of science and technology, optically variable inks are not only used for anti-counterfeiting printing of trademarks, but also for surface decoration of special products. The reason why the optically variable ink has the corner-changing color characteristic is that a pigment with a very special structure is used, and its particles are very thin flakes with a good particle size distribution. The production process of the pigment is as follows: under high vacuum conditions, according to the design requirements of a specific film structure, a variety of materials with different refractive indices are sequentially deposited on the same carrier to form an optically variable film, and then undergo crushing, grading, surface treatment, etc. . When the thickness of the film layer meets the interference conditions of light, the film layer will show a photochromic effect, that is, its color will change as the viewing angle of the human eye changes