Color change principle of photochromic pigment
photochromics reversibly alter their color upon exposure to ultraviolet sources. These chameleon-like dyes respond to natural solar irradiation as well as artificial sources such as 365 nanometer "black light." When sunlight or ultraviolet (UV) radiation is applied, the dye becomes excited and the molecular structure is changed allowing a color to appear. When the stimulus (sunlight/UV) is removed, the dye will return to a state of rest, which is its colorless form. Photochromic molecules are not reactive in their crystalline state and need to be dissolved in a solvent or polymer to function.
A. Photochromic Dye – optically grade material compatible with solvent based flexographic, UV, screen, offset, gravure and epoxy ink formulations.
B. Photochromic Pigment – microencapsulated photochromic dye for high temperature processes.