Breakthrough light-sensitive colorants

What is it about?

This paper provides an introduction to a type of light-sensitive dye which helped form the basis for the first commercially important application of photochromism. The discovery in the 1970s that spirooxazines generally possessed much better photostability than other photochromic colorants known at the time spurred on research into their use in sun-responsive ophthalmic lenses. This technology took off in the 90s when their use was coupled with that of the newly exploited naphthopyran dye class. The latter went on to displace much of the use of spirooxazines; nevertheless they remain of industrial and academic interest for many applications. This paper not only covers this history, but also outlines the basics relating to their light-responsive properties. as well as colour-activity relationships which many academics overlook when trying to exploit spirooxazines. In addition, it discusses their industrial manufacture in greater detail than other recent reviews. Finally, a flavour is given of the range of applications which are being explored with spirooxazines as functional colorants.

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Photo by MontyLov on Unsplash

Photo by MontyLov on Unsplash

Why is it important?

The discussion of spirooxazines has an unashamedly industrial perspective. Much has been published in academia on the class, including reviews concerning their chemistry and properties. However, most do not touch on the practicalities of their use at the sharp end of industrial manufacture and application: this paper does. The class also formed the basis for the first commercially successful exploitation of photochromic dyes. Despite what was learned and published concerning spirooxazine properties, many academic studies do not take advantage of this knowledge to get the best out of these colorants...this paper outlines some of the most industrially useful strategies for manipulating the photochromism of this dye type.

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