The spectral emissivity depends on the surface conditions of the materials. It is already known that the property of the spectral emissivity when an oxide film is formed on the metal surface differs from the property when there is no oxide film.
But, it is still unknown how thick oxide film is required in order for the spectral emissivity to show the property of oxide. In other words, the relation between the thickness of the different material on the metal and the spectral emissivity is not yet obvious.
This study is for the purpose of making clear above mentioned relationship.
Gold, greatly different from SUS304 in the wavelength dependency of the spectral emissivity, is evaporated on the SUS304. And the spectral emissivity is measured with the layer thickness varied in many degrees. The wavelength region covers the visible one and the neighboring, 0.38-0.90 μm that is often applied in measuring color temperature. The spectral emissivity is determined by the measuring spectral reflectance at room temperature.
Consequently, it is obvious that the spectral emissivity shows linear variations, depending on the gold layer thickness (below 0.02 μm), and that it shows asymptotic convergency to the characteristic value of gold (0.05-0.07 μm).
