NAPHTO (2,1-B) PYRANIC PHOTOCHROMIC COMPOUNDS WITH BI OR TERTHIENYL SUBSTITUTIONS, PROCESS FOR PRODUCING SAME, MATERIALS AND PHOTOCHROMIC ARTICLES OBTAINED

摘要

The photochromic compounds of the invention correspond to the formula:in which Th2 represents a bithienyl group in one of the positions 5 to 10 of the naphthenic ring system system, R1 denotes a bithienyl or trithienyl group and R2 denotes a bithienyl, trithienyl, aryl, naphthyl, thienyl, furyl, pyrrolyl or N-alkylpyrrolyl group.