Photochromic Properties of Spiropyran in Hard Coating Films Made by Sol-Gel Method

− Organic-inorganic hybrid solutions were made using glycidoxypropyl trimethoxysilane (GPTMS) and vinyltriethoxysilane (VTES) as starting materials by sol-gel method. Photochromic coating solutions were prepared by mixing the solution of photochromic dye (spiropyran) dissolved in ethylacetate with the organic-inorganic hybrid solutions. Photochromic films were prepared on polycarbonate sheets by spin coating and cured for 2 h at 100 oC. The resulting films exhibited a reversible color change upon irradiation with UV light from transparent to blue. The color-fading speed and pencil hardness of the coating films increased with increasing the GPTMS content in the coating solutions.