The appearance of watches is to facilitate people's lives, but reading time in dark places is still very troublesome, and must rely on other light sources. Visually seeing time is still one of the important reasons why people like watches. As a result, some people began to apply fluorescent materials on the hands and scales of the hands and dials, so that the time can be read conveniently at night.
The phenomenon of matter luminescence generally falls into two categories: one is that the substance is heated, and the heat is emitted to emit light, and the other is that the substance is excited by the absorbed energy and transitions to the excited state (unsteady state) and then returns to the ground state. The use of fluorescent coatings on watches is based on the second principle that fluorescent materials are excited to emit light.
Conventional fluorescent coating materials can be classified into two types: self-luminous type and light-storing type. The self-luminous fluorescent agent mostly emits a fluorescent agent by emitting a ray of a radioactive substance carried by itself. The light-storing type fluorescer is basically free of radioactive substances, but it needs to absorb and store enough external light to transfer its own electrons from low energy level to high energy level and store them. When the surrounding environment is dark, the self gradually releases the absorbed energy gradually. At this time, the electrons transition from the high energy level to the low energy level, and the fluorescent agent starts to emit light. Since the light storage type does not carry the radiation excitation material itself, the afterglow persistence is temporarily inferior to the self-luminous type.