Luminova
LumiNova is a brand of the Japanese manufacturer Nemoto & Co Ltd. , under which inorganic phosphorescent pigments are offered. The pigments are based on alkaline earth aluminates and were developed and patented by Nemoto. Under the name Super-LumiNova , a further development with increased luminosity is offered especially for the watch industry. LumiNova pigments are available in the luminous colors yellow-green, blue-green and blue-violet.
The pigments were developed in 1998 as an alternative to the self-luminous substances previously used, based on radium or later on tritium . In contrast to previous products, these pigments do not show any radioactivity and as a result are virtually non- degradable .
composition
According to the manufacturer, the pigments are based on strontium aluminate (SrAl 2 O 4 ). The crystal lattice is doped with europium , which serves as an activator for the optical effect. Other rare heavy metals are used as co-activators.
functionality
The pigments shine through inorganic phosphorescence . Excitation with artificial light or daylight raises electrons in the excitation centers to a higher energy level. These excitation centers consist of foreign atoms that are introduced into the crystals of the Luminova. The more intense and longer the exposure, the more complete the excitation up to saturation and the brighter the glow. With a certain probability / time the electrons fall back into the ground state and give off energy in the form of visible light.
This decay process lasts (essentially) for a characteristic time that is typical of the material. With a suitable mix of materials, a long light duration can be combined with a very high, but rapidly decaying brightness. The then very bright luminous hands can be easily read immediately after switching off the light or leaving a bright room, i.e. when the sense of sight is not yet adapted to the darkness, but also after a longer period of darkness, for example at the end of the Night.
properties
Coloristics
Two different color specifications are required to clearly identify the color of the luminous pigments: the color under daylight and the luminous colors. Luminous colors are z. B. green, yellow or red. In addition, there are different gradations of the luminous color from light to dark. Standard colors are listed in ISO 3157 and ISO / DIS 17514.
stability
Due to the fact that no chemical change has taken place after a charge-discharge cycle, the pigments theoretically retain their afterglow properties for an unlimited period of time. A reduction in light intensity takes place very slowly, almost imperceptibly. This reduction increases with the degree of coloration of the pigments. Intensely colored types (e.g. light green) lose intensity more quickly than neutral ones. High temperatures of up to several hundred degrees Celsius are not a problem. The only thing to avoid is prolonged contact with water or high air humidity, as this forms a hydroxide layer that has a negative effect on the light intensity.
toxicity
In contrast to tritium, which is also used in a bright color, strontium aluminate does not contain any radioactive substances. Since the pigments consist of an alkaline earth aluminate base, they show an alkaline behavior in contact with water. Otherwise, handling is to be classified as harmless in compliance with the current safety and hygiene regulations.
Applications
As with all phosphorescent pigments, the most popular application is the phosphorescent coating on watch faces. Here the pigments are used to make the pointers and numerals glow in the dark. It is also used on signs and boards to mark escape routes for emergencies.
Web links
Individual evidence
- ↑ a b Description of the product on the Nemoto company website ( Memento of the original dated December 5, 2008 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ a b c report on www.info-uhren.de (PDF; 37 kB)
- ↑ Patent EP0622440 : Phosphorescent phosphor. Published November 2, 1994 , Inventors: Yoshihiko Murayam, Nobuyoshi Takeuchi, Yasumitsu Aoki, Takashi Matsuzawa.
- ↑ RC TRITEC Ltd .: Special Colors
