Development of Self-luminous Materials in Watch Industry

In the dark night, if you want to know the moment at this time, you need to check your watch. Most of the watches now have the function of night light, so we can also see the time on the watch at night.

 

The function of night light of the the watch originates from the self-luminous material. The earliest self-luminous material in history is the zinc sulfide, which is a non-toxic and non-radioactive substance. Zinc sulfide itself does not shine, when it is illuminated by sunlight or light, will continue to shine for a period of time, but its luminous time is very short. To solve the problem of short luminous time, the watchmaker has been looking for a new material.

 

In 1898, Madame Curie discovered the radioactive element radium. This element brings good news to watchmakers, who mix radium with zinc sulfide, which glows on their own. Since the 1930s, most of the self-luminous or electroluminescent signs used in clocks and watches have been such materials. But radium elements are radioactive, if using radium to make self-luminous materials, it must be harmful to the human body. Early watchmakers made watches with this material without any protection, which made most of them suffer from cancer.

 

After the 1950s, chemical research institutions around the world gradually restricted the application of radium to ordinary fields. During this period, most watches were made of another self-luminous material, tritium. Tritium is an isotope of hydrogen and also radioactive, but its radioactivity is weaker than radium, so it is safer than radium. The half-life of the tritium is 12.5 years, that is, the effective life of self luminous exit signs home depot made with tritium is about 10 years. Ten years later, tritium began to turn yellow and gradually lost its luminous function.

 

In the early 1970s, Japan developed a self-luminous material. Although this material is also tritium dominated, it is not easily oxidized. Tritium is a kind of β particle radiators, and the range of fire of β rays is only 0.4 cm, and its penetration is very weak, it can not penetrate glass at all. This material is basically harmless to the user. But for the workers who make watches, they are exposed to a large amount of this material every day, which can cause harm to their bodies. As a result, watch makers also gradually reduced tritium use after the 1980s.

 

By the mid-1990s, a new type of self-luminous material was born, which is Luminova. Luminova is a non-radioactive environmental protection material. Its basic chemical composition is inorganic aluminate, it has the characteristics of strong light permanency, no discoloration, and very good chemical stability. After 10 to 20 minutes of light exposure, this material can continue to glow for 8 to 10 hours in the dark. This material is a kind of light storage and self-luminous material, which can only glow after being illuminated by light. It can accumulate light energy in the material and make it glow in the dark. The material emits more light than tritium, and has a service life of more than 25 years. Now all watches are basically made of this material.