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Kanagawa photocatalyst tile paint
Chigasaki City, Kanagawa Prefecture
Toto Ltd. 
Shimohigoshi, Mitsuhide (42)
Manager,Intelligent Materials Research Section Chigasaki City, Kanagawa Prefecture
Toto Ltd. 
Shimohigoshi, Mitsuhide (42)
Manager,Intelligent Materials Research Section
Development of Photocatalyst Technology and Expanded Application Range to Include Multi-purpose Tiles, Paints, and Building Materials
Toto Ltd. launched a joint study on photocatalysts with the University of Tokyo in the 1990s and commercialized anti-bacterial tiles utilizing “organic decomposition characteristics.” In 1995, they discovered “super-hydrophilicity,” a second photocatalyst function. By developing the “Hydrotect” technology to apply the functions of photocatalysis to coating agents, they realized self-cleaning performance for automatically removing dirt with rain or water.The scope of application for this technology has dramatically expanded through licensing in other fields of business including construction, road improvement, automobiles, glass, and atmosphere purification. Moreover, by adding silica to supplement water retention as well as silver to enhance bacteriocidal power, they have developed products that can demonstrate the same functions even in locations where less light is available. At the Aichi Expo, their water-based paint, “Hydrotect Color Coat,” received the “Global 100 Eco-Tech Award.”
In the process of conducting experiments or development, one can be sure to encounter a scene where “something changes.” You experience that change particularly when a product is completed.
read prize-winner’s documents
Company Profile
Toto Ltd.
http://www.toto.co.jp/en/index.htm
Established in 1917, Toto Ltd. began manufacturing sanitary ceramic equipment in Kokura, which is part of Kitakyushu City. Now, they are a major manufacturer specializing in water-related household products such as integrated kitchen systems as well as bath and toilet fixtures that occupy top shares of the domestic market. Even for a venturing manufacturer like Toto, who has developed such evolutionary products as the “Washlet” toilet seat, the photocatalyst-related business proved to be a truly unique, new business opportunity that exceeded the bounds of the company’s well-known field of specialization.
Measuring affinity using a contact angle gauge. On a photocatalytic coating, the angle between the water drop and the surface will be almost zero.
Measuring affinity using a contact angle gauge. On a photocatalytic coating, the angle between the water drop and the surface will be almost zero.
Wall on which ordinary paint and photocatalytic paint are alternately applied; the effect is quite obvious
Wall on which ordinary paint and photocatalytic paint are alternately applied; the effect is quite obvious
Working on an intra-industry product development utilizing the two major functions of photocatalysts
On a wall of the research center of Toto Ltd. (hereafter “Toto”) located in Chigasaki City, one can find one section with strange stripes consisting of brownish soiled areas and clean areas. In the clean areas, a magical paint is applied that induces a lazy process of decomposing dirt on the surface and washing it away with rainwater. Mr. Shimohigoshi is the leader of the project team that developed this revolutionary product. When titanic oxide is exposed to ultraviolet rays, it reacts with the moisture and oxygen in the air to form activated oxygen. This process, discovered about 40 years ago, is what is called a photocatalytic reaction. Activated oxygen has an “organic decomposition function” that decomposes bacteria, mildew, and dirt, while even eliminating nitrogen oxides. “The other major, revolutionary function of the photocatalyst—‘super-hydrophilicity’—was discovered in 1995 through our joint research with the University of Tokyo. To put it simply, this function has astonishing affinity with water, so when a drop of water strikes the photocatalyst, the water is not repelled at all but spreads flatly on the photocatalyst. The water is not simply there in a physical sense, but forms a very thin film of water at the molecular level. Even when you touch it, you can’t feel the wetness.” If that is the condition of a woman’s skin, it poses a serious problem, but scientifically, it is a revolutionary discovery. “Even when oily dirt is stuck to the surface, splashing water from the top, the water is attracted to the film of water on the photocatalyst, even penetrating through any surface oil. As a result, the oil floats above and can be washed away only with water, without using any detergent.” Up until that time, scientists and engineers thought that a strong water or oil-repelling property was needed to avoid soiling. Still, soiling occurs due to electrostatic discharge and other reasons. Having said that, it would be more practical to decompose the dirt and remove it with water (or rainwater outdoors) than completely prevent soiling. Transparent materials such as glass do not get fogged when provided with a super-hydrophilic film. When this discovery was first reported, a project team consisting of 10 experts from different fields in the company was formed to conduct product development at Toto’s basic research center. Their objective was to develop, with across-the-industry cooperation, a technology for coating the photocatalyst on various materials, so that it could be applied in as many fields as possible.
How to reconcile incompatible characteristics and conflicting principles
The principle is simple enough to deeply impress ordinary people. In the commercialization stage, however, the project team was confronted with the obstacle of conditions and methods of coating that had to differ according to the target materials. “Glass or tiles can withstand heat from 500°C up to 800°C, so you can burn titanic oxide into the surface, but the problem was how to handle resin materials like plastics.” For resins to which high temperature baking cannot be applied, something that hardens around room temperature, such as paint, was conducive to application. The application to plastics would be wide-ranging and expected to account for the largest volume of photocatalyst products. However, there was one fundamentally serious problem: plastic is an organic compound, and the main property of the photocatalyst is nothing other than the decomposition of organic materials. What is even worse is that paint itself is organic in the first place. “Against this background, we tried to coagulate titanic oxide by mixing it with glue or an inorganic silicon system binder material. In fact, this was the method we adopted when the super-hydrophilicity of the photocatalyst was discovered. At that time, we were thinking about preventing dirt by combining silicon’s water-repelling property and the photocatalyst’s decomposing property, but this actually led to the discovery of super-hydrophilic characteristics. We could thus utilize the result of that failure, or as we think of it now, that success.” They also provided a barrier layer between the binder and plastic to prevent decomposition. Thus, the coating of the photocatalyst became possible even on resins or painted surfaces, thus rapidly expanding its scope of application. Behind this huge success lie the efforts of the project members who went through the countless cycles of trial and error. “There were 10 members of the project team itself, but in fact, many more people were involved in the development. Some, for example, simply mixed dozens of kinds of silicon materials for hours and hours. Such repetitive work in itself is not rewarding at all. Therefore, we always encouraged all staff involved in the development to be conscious of the ultimate goal that our product development would help us reach.” A sense of dissatisfaction occurs if one fails to grasp the big picture of the project simply because what one does seems insignificant. That is because, even in such a process, one could surely encounter a scene where “something changes” without fail. Mr. Shimohigoshi endeavored to share such a moment with all people involved in this development.
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[Other prizewinners (in Japanese syllabic order)]
Toto Ltd.: Hironaga Iwata, Junji Kameshima, Atsushi Kitamura, Eiichi Kojima,
Yoshimitsu Saeki, Makoto Hayakawa, Toto Materia: Hideki Kobayashi, Japan
Hydrotect Coatings Co., Ltd.: Tatsuhiko Kuga, Toto Frontier Research: Yukio Takano
About this site (C)2006 The Japan Machinery Federation
The contents are based on the information as of 2006/03/31. This project is subsidized by the Japan Keirin Association