When it is dark or completely dark, some clocks still allow you to read the time thanks to the illuminated indications. This is called watch luminescence. To allow this, the manufacturer applies a special material to the hands, numbers and / or indexes, thus combining chemistry with watchmaking.
The birth of luminescence.
She appears on day 19th century, then we talk about radio-luminescence. The first luminous clocks contain radioactive materials such as radio. However, the risks to workers related to the management of the latter are significant, and it was finally banned in 1963. The radio is replaced by tritium, which is slightly radioactive but is not supposed to be harmful to health.
Later, in the 1990s, the Luminova was invented by the Japanese company Nemoto. This new phosphorescent pigment technology has the advantage of not being radioactive. It is used in watchmaking, but also in the field of signage.
Finally, the SuperLuminova appeared in 2007 and was completely reserved for watchmaking.
The different types of luminescent treatments.
It is a radioluminescent material that contains tritium, a variant of hydrogen. Much less harmful than the radio, it is still slightly radioactive.
It emits light continuously for 12 years, a period corresponding to its half-life, since it will then lose its luminosity.
The radio is mainly in diving or military watches. It is subject to strict regulations (ISO 3157). Prohibited in France since 2002, you can still find it by buying old watches.
LumiNova and SuperLuminova
Found in most watches today, this phosphorescent paint composed of strontium aluminate is neither toxic nor radioactive. It works like an accumulator, that is, it can store natural or artificial light and then restore it when it is dark. Therefore, this process offers infinite use since the material does not age but only needs to be recharged.
Luminova is used in signage and watchmaking.
SuperLuminova comes after Luminova in 2007. Unlike the previous one, this material is completely reserved for the field of watchmaking. It also has higher brightness.