Patent ID: 7327074

Claim:
An illuminating device for use in a tunnel, comprising: a device body having an open side; a light source mounted within said device body, said light source emitting light through the open side of said device body; a frame attached to said device body; a transparent cover detachably mounted within said frame, said transparent cover having a first surface facing said light source and a second opposing surface; a precoat film deposited on the second surface of said transparent cover, said precoat film being composed of a silica film; and a titanium dioxide film having first and second opposing surfaces, the first surface of said titanium dioxide film being formed on said precoat film, a light transmittance of said titanium dioxide film being at least 50% for light having a wavelength of 550 nm, the light transmitted from said light source through said transparent cover, said precoat film and the first surface of said titanium dioxide film to the second surface thereof causing photocatalytic activity to be generated on the second surface of said titanium dioxide film.