Glow-in-the-dark
Glow-in-the-dark (English, for "glow in the dark") is a term for products and articles that glow in the dark, which is mainly used for jewelry , accessories and decorative items where the source of light is on the is not apparent at first glance.
Types of light generation
The light can be generated in different ways:
- Some products use electrical energy from a battery and generate light using light-emitting diodes or electroluminescent foils .
- It can be the phosphorescence be exploited, that is, to some substances that in artificial or natural light "recharge" and then afterglow over a certain duration.
- The light can be generated by a chemical reaction: chemiluminescence . These products (e.g. so-called " glow sticks ") are mostly made of soft plastic, and inside there is a glass ampoule that breaks when the product is bent. A reaction occurs by mixing the reactants. Gel-like materials are used to prevent oxidation that is too rapid. An example of such a reaction is the oxidation of luminol .
- In some products, especially the hands and dials of clocks and other instruments, as well as in the signage of emergency exits, one also finds radioactive substances whose radiation triggers luminescence in a fluorescent material . In the past, radium paint was used for this , later the hydrogen isotope tritium , a beta emitter . In the early 1920s, due to inadequate protective measures, the radium-containing luminous paint caused serious health damage and even deaths among the workers who painted the dials, the so-called radium girls . In addition to fluorescent paints containing tritium, there are also tritium gas light sources in which tritium gas is enclosed in thin tubes; these relatively bright light sources are also known under the trade names Traser® , Betalight® and Nite Glowring® . In contrast to radium, tritium is harmless as long as it is not released and incorporated , because the maximum energy of the electrons (beta rays) is only approx.18.6 keV and therefore the range ( penetration depth ) of the electrons in solids is only approx. 10-100 nm . Nevertheless, tritium is increasingly being replaced by Luminova and Superluminova , since these luminescent substances do not have any radioactive radiation.
Individual evidence
- ↑ www.oysterinfo.de - Homepage for watch lovers with a detailed report on various luminous materials (including tritium) ( Memento from December 25, 2011 in the Internet Archive ).