| 摘要 |
PURPOSE:To maintain the transmittance of IR rays at >=80% and to improve environmental resistance (gaseous sulfurous acid test) by coating the surfaces of AgBr, AgCl, TlI, TlBr with an antireflection film made of polyethylene (PE). CONSTITUTION:The refractive indices (10mum wavelength) of the AgBr, AgCl, TlBr, and TlI are respectively 2.1, 2.0, 2.2, 2.4. On the other hand, the refractive index of the PE is 1.5 (10mum wavelength). Then, the refractive index of the PE is lower than the refractive index of a silver halide and thallium halide and, therefore, an antireflection effect is obtd. and the transmittance improves if the surfaces of the silver halide and thallium halide are coated with the PE in such a manner that the optical film nXd (n is the refractive index of the PE, d is the film thickness of the coating) attains odd times lambda/4 (lambda is a wavelength). Not only the antireflection effect but also the environmental resistance (particularly the gaseous sulfurous acid test) is improved by the chemical resistance of the PE and the ability to prevent the advance of moisture, etc. |
