Development of Luminous material on Watch

Long before radium was discovered, the French discovered that zinc sulfide can emit faint fluorescence in a dark environment after being irradiated by strong light. This is because zinc sulfide has phosphorescence characteristics and can be excited by strong light. Self-luminous, but the brightness and duration are very short. However, after radium was invented, a more powerful luminous effect can be achieved by mixing radium with zinc sulfide.

This invention was applied to watches by Panerai in 1915, and applied for a patent in August of the same year. In the same year, the Italian Navy equipped a large number of watches coated with this new luminous powder. Since then, military watches have generally used it. (RA to be marked on bottom of Watch Dial)

RA SWISS MADE RA

After more than half a century of invention and exploration, the luminous materials of modern watches are basically divided into two categories.
1. self-powered luminous materials, Most of the self-luminous materials rely on the traces of radioactive substances carried by themselves to release rays to stimulate the fluorescent agent to emit light. such as BALL Micro gas tube, (H₃)
2. light-storing materials. NEMOTO and SuperlumiNova.

The light-storage material basically does not contain radioactive substances. Just like a battery, it excites the fluorescent material to emit light by attracting sufficient intensity of external light. Compared with the self-luminous material, the brightness and light time of the light-storage material are not as good as the former.

Ray-zinc sulfide material is obviously a self-luminous material, and due to the limitations of early watchmaking technology, the waterproof performance of the watch is average. After water and air enter the watch, it will chemically react with radium, which makes the luminous effect of radium worse. even the dials were radiated by this radium. pls see below photo.
In 20 years or so there were no more night lights. But it is undeniable that radium is a milestone in the opening of reading time at night.
radiation watch dial

As the hazards of radium became more and more widely known, the use of radium in watches was gradually stopped. In 1949, Panerai replaced the radium-containing paint with a new self-luminous technology Luminor, and registered a patent with "Luminor" as a trademark on January 11 of the same year.

Another radioactive element "tritium" (sound 'chuān' in Chinese, English is Tritium) is used in this luminous technology. Tritium is much safer than radium. The half-life of tritium is only 12.5 years, so its luminous time limit is also limited. Basically, after about 15 years, it starts to age, turn yellow, and gradually lose its luminous effect. And this did not prevent tritium from directly replacing the use of radium in the following decades.

Tritium tube

In the 1960s, the invention of tritium tubes completely replaced radium and became the main material of self-luminous watches. The tritium tube does not require external energy or reflection of external light sources, it can remain stable all the time, and its luminous intensity is 100 times that of traditional luminous paint. And the radiation of tritium is very small, as long as the tritium tube is not broken, it is harmless to the human body.

Tritium gas tube

Tritium glass tube watch

Although the radiation of tritium is small, people now need safety psychology and environmental protection requirements. As a result, a new type of long-lasting light-storage rare-earth alkaline-earth aluminate fluorescent material that does not contain radioactive substances has emerged. It does not contain any harmful elements at all, and has more stable chemical properties, high brightness, and long afterglow time.

In the early 1990s, Japanese Harada Kenzo (Nemoto Kenzo) invented a new luminous paint and named it LumiNova, which is a light-storage material that does not contain any radioactive elements. Harada Kenzo established himself based on this patent. Nemoto & Co., a famous luminescent paint company, which was very popular in World

Luminova means "luminous" in Italian. Its basic chemical composition is inorganic aluminate, which has strong light resistance, will not change color for a long time, and has relatively good chemical stability. After 10 to 20 minutes of natural light exposure, it can continue to glow for 8 to 10 hours in a dark place. But such brightness is far from enough for diving watches.

Later, Harada Kenzo and the Swiss company RC TRITEC Ltd. jointly developed the Super-LumiNova light-storing material. Compared with the previous LumiNova, it has higher brightness and longer afterglow. With this invention, the two joint-venture Swiss companies LumiNova AG Switzerland Established and started supplying raw materials to Swiss watches. (mainly the Super-LumiNova BGW9 or C3 or C1 to be available on Watch Dials or Watch Hands)

lume watch hands and dial

At present, the vast majority of watch brands in the world basically adopt Super-LumiNova, a luminous solution, which has good safety, brightness and afterglow characteristics. After all, tritium gas tubes still have certain limitations in terms of shape and half-life.