What is Lumibrite Exactly...
Authored by Ikuo Tokunaga
(the designer of many of the best known classic Seikos), regarding what Lumibrite luminous paint is exactly and how it was adopted for use in 1996. The original complete thread can be found in the SCWF mirror site here: http://www.larrybiggs.net/scwf/index...&id=1039051508
About the luminous paints of Seiko watches, "Radioactive luminous paint" which uses a radioactive material was abolished five years ago in all watches including the diver's watches. We had switched to non-radioactive "Photo-luminescent paint" with high safety extensively.
The "Radioactive luminous paint" which was being used in Seiko watches before was not "Tritium" but "Promethium = 147Pm". Since the quantity of the radioactive material which can be used for one watch is restricted and radiation energy decreases, in the case of the watch used around 10 years, energy will become weak and luminous paint will not shine.
The "Photo-luminescent paint" of Seiko watches is called "LUMIBRITE" (trademark), and is made of SrAl2O4 + Eu + Dy. We can use it without any restriction, excluding the above dangerous radioactive materials at all, and it can continue shining several hours and the most important feature of this luminous paint is safety for the users. Although the old photo-luminescent paint disappeared for a short time, in case of "LUMIBRITE", when it shifts to darkness from a general living environment (conditions which light hits for 10 minutes in the illumination of about 500 lx), it will shine for about 3 to 5 hours by after glow of light in case of general grade "LUMIBRITE", and in case of the highly efficient "LUMIBRITE" used for diver's watches and adventure watches etc., it will shine for about 5 to 8 hours in darkness. If even light has hit, long periods of use can be performed repeatedly any number of times, and there is little degradation in this paint, therefore "LUMIBRITE" is an excellent luminous paint for watches. (See the following figure).
Comparison of the luminous paints:
SEIKO Professional 1000m: