COLOR DEVELOPMENT METHOD FOR PHOTOCHROMIC MATERIAL

摘要

PURPOSE:To enable efficient color development using a small output light source and to obtain superior repetition characteristics by using light specified in wavelength as the irradiation light for color development of the photochromic material containing a fulgide-derived compound. CONSTITUTION:The photochromic material to be used contains the fulgide- derived compound represented by formula I in which X is an O or S atom; each of R1 and R4 is H or lower alkyl; each of R2 and R5 is lower alkyl; and each of R3 and R6 is alkyl. The irradiation light to be used for the color development contains light in the wavelength region of 320 - 450 nm in an amount of >= 80 % in wavelength region of <= 650 nm, and comprises continuous wavelength light and discontinuous wavelength light having line spectrum.