PHOTOCATALYST, LIGHT SOURCE AND LIGHTING DEVICE

摘要

A light-transmitting cover (9) is so provided as to cover a high voltage sodium lamp (11) which emits at least visible light and light whose wavelength ranges 300 nm - 400 nm. A photocatalyst film (13) is so formed at least on one of the inner and outer surfaces of the light-transmitting cover (9) in such a way that the visible light does not interfere with each other. The main component of the material of the photocatalyst film (13) is titania (TiO2) whose visible light transmissivity has its peak at a wavelength approximately equal to the peak wavelength of the visible light of the high voltage sodium lamp (11). Oxidation and decomposition of substances are accelerated by ultraviolet radiation emitted by the high voltage sodium lamp (11) with the photocatalyst film (13), and contamination of the light-transmitting cover (9) is avoided. Even if the thickness of the photocatalyst film (13) is increased in order to improve the photocatalytic action, the peak wavelength of visible light emitted by the high voltage sodium lamp (11) is transmitted through the photocatalyst film (13) efficiently and the degradation of the lighting efficiency is suppressed.