Photochromism of Naphthopyrans Possessing a Spirophenanthrene Unit and the Ophthalmic Lens Comprising of Them

Abstract

In this chapter, the photochromic properties of naphthopyrans applicable to plastic photochromic lenses are described. In particular, introduction of electron-donating groups on the skeleton of a naphthopyran, 3,3-diphenyspiro[benzofluorenopyran-cyclopentaphenanthrene], and their effects are discussed in detail. Introduction of a methoxy group to C6 caused the bathochromic shift of the absorption band of the MC form. Further introduction of methoxy groups to the para-position of the phenyl groups on C3 induced faster decoloration of the MC form. Additional introduction of a methoxy group to C11 increased the absorbance. These naphthopyrans, however, showed poor photochromic properties in a solid matrix compared with those in solution. The matrix design of the plastic photochromic lenses to make the most of the potential property of naphthopyrans as well as to maintain the required properties as ophthalmic lenses is also described.