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Column No.1 "Luminous watches/clocks and Nemoto"(Aug. 20, 1999) According to an ancient document from the era of Chinese Emperor, Zhao Tai Zhong, the first luminous paint was invented in Japan over 1,000 years ago. The document, (Displayed at the Palace Museum in Taipei, Taiwan) tells of how the emperor heard of a painting which showed a wonderful cow drawn on the wall of a cave. Apparently, the cow could not be seen in the daytime because "it went to a meadow for eating", and "returned to the cave in the evening". Ordered to investigate, one scientist learned that, "the cow was painted with special paints made from shells in the sea." This phenomenon is more easily explained today. The Japanese paints must have contained a phosphorescent pigment to achieve the 'glow-in-the-dark' effect.  In 1908 a luminous paint containing radium was developed and the first luminous watches and clocks were produced in the United States. Similar watches appeared in Switzerland by 1911. In Japan, Seiko started production of watches and clocks in 1895, but didn't produce a luminous watch until 1927 and Seiko's first luminous alarm clock didn't appear until 1931. Nemoto was established in December of 1941 for the manufacture of luminous paints and coatings. Originally, radium had been added to phosphorescent paints to enable them to glow for extended periods. In 1960 Nemoto developed N-Luminous paints that contained Promethium. As a result, luminous watches and clocks became much more popular. N-luminous paints were safer, brighter and much less expensive than luminous paints containing radium. Japanese watch and clock manufacturers who used the N-paints were able to export a large quantity of luminous watches and clocks. N-luminous paints contributed greatly to the progress of the Japanese watch and clock industries. At the height of the market (1984), 10 million luminous watches and 12 million luminous clocks were produced in Japan.  As environmental awareness has increased, production of radioactive luminescent watches and clocks has decreased significantly. Despite this trend being good for the environment, it caused a crisis for radioactive pigment makers. Nemoto's invention of LumiNova (1993) solved the environmental problems that radioactive luminescent pigments had caused. Without the aid of a radioisotope, LumiNova glows brightly for extended periods. Watch and clock makers all over the world quickly switched to LumiNova, and global sales of luminous watches and clocks rebounded nicely. Nemoto is very gratified to know that the original invention of, and the recent innovation to luminous pigments both occurred in Japan. |
