Why can't highlighters glow?

Since the highlighter only emits light when exposed to ultraviolet rays, we usually use it normally, and it will not emit light at all.

And not all the highlighters used will emit light. If you want to make them glow, you can use a UV light. If not, use a small money detector light. Take a real highlighter and write a few words on the paper, and then use the UV light or Irradiate the money detector light for 1--2 minutes. Finally, if you observe carefully in the dark place, you will find that the words emit a weak light. If you can't see it, you can do this test again at night, and then turn off the light to observe.