To prevent the direct contact of a packing with a photocatalyst film when a cover body is supported through the packing and prevent the deterioration of the packing caused by photo-catalytic activity by forming a protecting film on the surface of the photocatalyst film in a packing contact part in the cover body.
A photocatalyst film 31 is formed on the whole surface or in a region where light from a high pressure sodium lamp reaches, in an intermediate layer mainly comprising silica (SiO2) on the outer surface of a cover body 20. A protecting film 33 is formed so as to cover the surface of the photocatalyst film 31 in a packing contact part 32 coming into contact with a packing 17 of the periphery of the cover body 20. Although the packing contact part 32 of the cover body 20 comes in contact with the packing 17, their direct contact is avoided since the protecting film 31 is interposed between the packing 17 and the photocatalyst film 31, and the deterioration of the packing 17 caused by photo-catalytic activity can be prevented.
WATANABE TSUTOMU
KAMATA HIROSHI
SAITO AKIKO
KOJIMA HIROYUKI
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