| 摘要 |
PURPOSE:To form an oxidized film with little peeling off and excellent withstand voltage characteristics and capable of preventing the generation of rust by making the iron composition ratio of a shadow mask mainly composed of iron and nickel in excess of the original iron composition ratio and eliminating a gap in the boundary between the oxidized film and a basis material so as to form the oxidized film excellent in thermal stress. CONSTITUTION:By applying electrolytic polishing to a basis material mainly composed of iron and nickel, its surface is made to have excess iron in existence than the original iron composition ratio. This is caused by the fact that nickel ions on the metal surface layer are preferentially dissolved out and on the contrary anode-dissolved iron ions are deposited on the metal surface due to the difference of an anode dissolution speed and a diffusion speed between the iron ion and nickel ion. When an aimed oxidized film is formed on such an electrolytic polishing surface, the vicinity of the substrate approaches the state of the basis material mainly composed of iron, thereby its stress due to thermal expansion is applied via an intermediate layer and becomes comparatively gentle, thus obtaining a firm oxidized film with a sufficient thickness. |
