The mystery of the color-changing glasses is in the glass. This special glass is called "photochromic" glass. In the manufacturing process, it is pre-doped with light-sensitive substances such as silver chloride, silver bromide (collectively referred to as silver halide), and a small amount of copper oxide catalyst. The spectacle lens has changed from no color to light gray, brownish brown, and then changed from black glasses to ordinary glasses, which is the magic of silver halide. In the glass of the color-changing glasses, there is a change process similar to the exposure imaging of photographic film. The silver halide is decomposed by light and becomes a lot of black silver particles, which are evenly distributed in the glass. The glass lens is therefore dim and blocks light. This is black glasses. However, unlike the case on photographic film, The silver atoms and halogen atoms formed after the decomposition of the silver halide are still tightly twisted together. When returning to a slightly darker place, under the promotion of the copper oxide catalyst, the silver and the halogen are recombined to form silver halide, and the glass lens is again Become transparent.
The silver halide is always in the glass, and the decomposition and compounding reactions are repeated indefinitely. Photographic film and photographic paper can only be used once, but the color-changing glasses can be used all the time. The color-changing glasses can not only become darker and clearer with the intensity of light, but also absorb ultraviolet rays harmful to the human eye, which is indeed the top grade in the glasses. If you change the window glass to photochromic glass, the sun will not shine in the room on sunny days; in some high-end hotels and restaurants, color-changing glass has been installed. The car's cab and the window of the tour bus are equipped with this kind of photochromic glass. In the direct sunlight, even the color-changing glasses are not worn, and the car has always maintained soft light, avoiding the dazzling sunlight and exposure, everyone should be What a joy!