Photochromic naphthopyran compounds: compositions and articles containing those naphthopyran compounds

摘要

A photochromic naphthopyran displays good color distribution when the naphthopyran has a central nucleus of the formula: wherein F is a 5-member, 6-member, or 7-member heterocyclic ring group having only one heteroatom, the heteroatom selected from the group consisting of oxygen, sulfur, and nitrogen, the 2,3 or 3,2 positions of the heterocyclic ring fused to the g, h, or i side; R₁ and R₂ are the atoms or groups providing photochromic properties to the naphthopyran.