From radioactive radium in the 1940s through to the Swiss Super-LumiNova pigments currently used, the development of phosphorescent materials for the watch industry has evolved constantly.
As the undisputed leader in this field, the Appenzell-based company LumiNova created quite a stir at the latest EPHJ-EPMT-SMT subcontractors and suppliers trade show. Long confined to blue and green for reasons relating to the composition of the ingredients, the company created in 1934 presented pink, yellow, orange and dark blue shades this year, after introducing white and purple in 2017. This colour palette enables veritable luminescent compositions on dials.
A joint venture between Japanese company Nemoto and RC Tritec of Appenzell, Switzerland, LumiNova produces phosphorescent coatings – that shine in the dark – and fluorescent paintings – that are luminous even in daylight – for almost the entire Swiss industry, as well as for other fields of application, such as police car safety markings. Whereas the range of day-view colours encompasses around 3,000 nuances, night-view shades are far trickier to achieve. The latter depend on the nature of the crystals involved in their composition, which is why blue and green long remained the only two options available.
The company certainly shook things up with the presentation of these new hues. “These are new crystals”, said Albert Zeller, RC Tritec’s CEO. “Based on strontium aluminate or calcium aluminate combined with rare earth metal, they are very difficult to obtain.” Each grain of Super-LumiNova acts like a mini-accumulator. When exposed to light, the electrons vibrate and reach a higher energy level. The energy thus released emits light. During the entire process, the key is to excite a maximum number of electrons, before delaying their deceleration for as long as possible. “We have patents pending for these new pigments, which have twice the glow”, added Albert Zeller.
Fédération de l'industrie horlogère suisse