The photochromic lenses: photochromic materials
Photochromic phenomenon is by changing the light absorption properties of lens material, make the lens absorption energy due to density changes occurring in the course of a chemical reaction. Its basic principle is to make the photochromic materials under the influence of ultraviolet (uv) radiation color darker, colorless state to recover by ultraviolet (uv) radiation to disappear; While under the influence of high temperature surrounding color becomes weak, the two process is reversible. This phenomenon is by activating material of photochromic material mix molecules. Commonly used in sunglasses. Photochromic materials early color glass lens is the silver halide photochromic materials used. When silver halide is applied to the lens material, under the uv rays and purple light, silver halide can be decomposed into silver atoms and halogen free; When the light source and ray disappear, silver and halogen atom has combined into silver halide. Silver halide is not decomposed is almost transparent, is broken down by chemical after the lens is dark. The decomposition and synthesis process is reversible chemical cycle again. Generally after 30 000 times or so after the cycle of color changing effect will be lost. For manufacture photochromic lenses ( Color piece) , manufacturers to consider the main condition is: 1. The degree of lens darker and fade; 2. Color change rate.