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World's First Frosted Light Bulbs

An invention of global importance, on a par with the drawn-wire tungsten bulb developed by Dr. Coolidge and the gas-filled bulb developed by Dr. Langmuir.

World's First Frosted Light Bulbs

Thomas Edison invented the incandescent lamp in 1879, incorporating a filament prepared by carbonating cotton fiber. Subsequently, in order to make long-lasting filaments, he gathered thousands of different materials from around the world and found that madake bamboo from Iwashimizu- Hachimangu in Kyoto was the best. He then developed practical carbon-filament light bulbs using madake bamboo for the filaments. This marked a turning point for the rapid development of electric lighting in Western countries.

In Japan, Tokyo Electric Light Company (the predecessor of Tokyo Electric Power Company) was established in 1883, and Dr. Ichisuke Fujioka, a professor at The Imperial College of Engineering (the predecessor of the Faculty of Engineering of The University of Tokyo), was invited to join the company as chief engineer. By 1888, several thermal power plants had been completed in succession and the number of electric lighting users finally began to increase. The reality was, however, that the key components—the light bulbs themselves—were all foreign products.

Fujioka therefore established a company called Hakunetsusha (one of Toshiba’s predecessors) in 1890 for the domestic production of light bulbs. The filaments were initially made using cotton thread, but it was found that incandescent bulbs suitable for practical use could not be produced by this method. Hearing that Japanese madake bamboo had been adopted as a filament material in the U.S., Hakunetsu-sha immediately started using it and, as a result, succeeded in manufacturing light bulbs for the first time in 1890. Although the production volume reached the level of 3,000 bulbs per month by 1892, they were not competitive in terms of price and foreign products continued to hold the largest market share. Several years later, in 1900, the company succeeded in manufacturing carbon filaments made from cotton and the volume of production rapidly increased.

In 1911, Dr. William Coolidge’s invention of drawn-wire tungsten filaments at General Electric Company (GE) in the U.S. was reported, and Hakunetsu-sha also started production and sales of bulbs incorporating drawn-wire tungsten filament. The development of this drawn-wire tungsten filament led to a fundamental improvement in material strength and uniformity of quality, and had a major impact on bulb manufacturing supported by the development of gas evacuation equipment for bulbs. Dr. Irving Langmuir of GE subsequently discovered that the life of a bulb depended on the evaporation of tungsten from the filament. Based on the hypothesis that the life of the filament could be extended by slowing this evaporation, in 1913 he invented a tungsten bulb filled with nitrogen gas, which does not chemically combine with tungsten. Upon hearing the news of this invention, Hakunetsu-sha immediately began to import and sell these bulbs in Japan and started making its own prototype. In 1915, it succeeded in manufacturing light bulbs filled with nitrogen gas.

With the appearance of gas-filled tungsten bulbs, the efficiency of bulbs was enhanced and both their luminous intensity and surface brightness became increasingly high. As a result, glare became a major problem in the field of general lighting. The first countermeasure taken to deal with this problem was frosting of the exterior surface of the bulbs. A drawback of this method, however, was that the surface became easily soiled and cleaning was difficult, leading to a rapid decrease in the amount of light transmitted. One of the company’s engineers, Kyozo Fuwa, then had the idea of frosting the interior surface of the bulbs and conducted research into this method. Unfortunately, glass bulbs with a chemically frosted interior surface turned out to be very fragile and unsuitable for practical use. After further strenuous research efforts, in 1925 he finally succeeded in manufacturing light bulbs with a frosted interior surface that were equivalent in strength to bulbs with exterior frosting.

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