Mirrors play an important role in watches, and through development and evolution, they have become wear-resistant and scratch resistant. The technology of synthesizing sapphire was invented in the 19th century and has been applied to watches since the 1960s. Sapphire has become a commonly used material for watch mirrors. The main component of sapphire watch mirrors is aluminum oxide, which removes impurities such as iron oxide and titanium oxide. Compared with other mirror materials, sapphire has a Mohs hardness of up to 9, making it less prone to reflection and scratches.

1. Production process

Aluminum oxide is a raw synthetic sapphire made from pure alumina at high temperatures, which is then cut into disks using diamond tools and polished into mirrors. After obtaining the original synthetic sapphire, it needs to be roughly sliced and polished to make it transparent. Polishing is carried out on a large milling machine until the thickness meets the standard. Operation: Cutting, grinding, chamfering, and polishing all require the use of drilling tools or diamond grinding paste. These processes are full of challenges. Common defects during the polishing process include bubbles, lines, etc., which can only be discovered after the lens is completely polished.

2. Mirror coating

The surface of the sapphire watch mirror is coated with an anti reflection film, which can be used to reduce reflection and enhance the visual effect of the dial. Heat a composite mixture of alumina (Al2O3), magnesium fluoride (MgF2), and hafnium dioxide (HfO2) under vacuum conditions to 1800 degrees Fahrenheit. When gas comes into contact with a mirror, it condenses on the surface, which is the principle of anti reflection film applied to the mirror.

The above is the production and mirror coating of sapphire watch mirrors. Although sapphire is scratch resistant, it is also very fragile. If it breaks down, the repair cost will be relatively high. In addition, the watch mirror is a powerful fingerprint collector, so it needs to be wiped frequently to ensure the brightness of the watch mirror.