Glow in the dark materials are divided into two types: self-luminous and light-storing. The basic composition of self-luminous luminous materials is radioactive materials, which do not need to absorb energy from the outside and can continuously emit light, not only at night but also during the day. Because it contains radioactive materials, it is very limited in use, and disposal after disposal is also a big problem. Zh
Light-storing noctilucent materials rarely contain radioactive materials, and there are no restrictions on their use, but they need to absorb external light energy to emit light, and they must store enough light energy to ensure that they always emit light. Another drawback of light-storing luminous materials is insufficient brightness.
For example, zinc sulfide has been used as a light emitter, but the light emission time is too short, and the brightness is not enough. As a result, a radioactive element, thorium, was later incorporated, and the luminous effect was ideal, but the intervention of radioisotopes did not meet the requirements of environmental protection.
Noctilucent materials are made of luminescent materials. The main luminescent element is a rare earth compound, so they are also called rare earth luminescent materials. In order to distinguish them from zinc sulfide luminescent powders on the market, they are called long-lasting afterglow luminescent powders. Glow in the dark powder luminous principle: The main feature of luminous powder is that it can absorb energy under sunlight or light for 5-20 minutes, convert the absorbed light energy and store it, and release the stored energy in a dark place.