Industrial organic photochromic dyes

Organic photochromic molecules are well established as colorants in the manufacture of niche products, providing striking colour change effects when irradiated with light. This paper describes the industrially important classes of photochromic dye in terms of their development and chemistries, the applications in which their photochromism is employed commercially, and the technical features behind their success. Photochromic systems form the subject of much industrially funded research into nascent high‐tech applications that have the potential to become the most commercially significant outlets for photochromic dyes. Those types being scrutinised are therefore also discussed along with the directions in which the industrial use of photochromic colorants may take.