[in Japanese]

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Test methods for photocatalytic materials were developed for national and international standards under a close cooperation among academic, industrial and governmental sectors. Eleven Japanese industrial standards (JIS) are already enacted and they are also proposed and discussed in ISO/TC 206. New test methods are being developed for visible-light-responsible photocatalyst. These activities are reported here together with the world trend, especially in Europe and Asia, of standardization, related measures for dissemination of products, and future prospects.

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Decomposition of organic compounds and hydrophilic conversion catalytically proceed on titanium dioxide (TiO₂) surface under ultraviolet (UV) light. However, the applications of the photocatalytic reactions have been restricted to UV light intensity. Hence, photocatalytic materials sensitive to visible light have been developed to obtain the photocatalytic effects, such as bactericidal, self-cleaning and air-cleanup effects, under light condition in indoor space. We have recently designed and fabricated efficient photocatalysts sensitive to visible light, Cu(II)-grafted TiO₂ and WO₃.

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Tungsten oxide loaded with nanoparticulate platinum (Pt-WO₃) is demonstrated to exhibit high activity for the decomposition of organic compounds both in liquid and gas phases ; the activity was almost comparable to that of titanium oxides (TiO₂) under UV light irradiation, and much higher than that of nitrogen-doped TiO₂ under visible irradiation. The high activity of Pt-WO₃ was found to be due to the promotion of multielectron reduction of O₂ to hydrogen peroxide (H₂O₂) on the Pt cocatalyst

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In the printing industry, offset printing technique is widely used method to print newspapers, magazines and other materials. In order to print the materials, offset printing plate is supposed to be fabricated as a master. Although aluminum substrate based offset printing plate, PS plate, is commonly used, the fabrication process has some problems : strong basic waste from the development process is discharged, and the aluminum substrate must be discarded after printing.
In this work, we have fabricated photocatalyst (TiO₂) -based offset printing plates on aluminum and titanium substrates, respectively. The printing plates were fabricated by the combination of four steps : 1) TiO₂ and organic layer were deposited on the substrates, 2) water-based ink patterns as a photomask were deposited by ink-jet printer on the substrates, 3) UV irradiation to decompose organic layer due to the photocatalytic reaction of TiO₂, 4) water washing to remove water-based ink patterns. We, in actual, have succeeded to print in color, and black and white using the fabricated printing plate. Interestingly, the fabricated offset printing plate can be renewed by a removal of organic layer under UV irradiation. The renewed printing plate demonstrated the high quality printing as well as initial one. This methodology to fabricate photocatalyst-based offset printing plates offers a new, resource-saving, environmentally friendly printing method.

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