| abstract |
(57) Abstract: A method for producing a low birefringence polyimide film having small polarization dependence is provided. A method for producing a low birefringence polyimide film in which a polyimide plate is used as a substrate in a polyimide film formed on a substrate, a polyamic acid solution or a polyimide solution is uniformly applied to the surface of the substrate, and then heat treatment is performed. As a general manufacturing method, a polyamic acid solution or a polyimide solution is applied on a polyimide plate by a spin coating method, a dipping method, or the like so as to have a uniform thickness. After that, the solvent is heated for evaporation. When a polyamic acid solution is used, heating required for imidization is further performed. [Effect] Compared with a polyimide film formed on a silicon substrate or an aluminum substrate, birefringence is small, and if an optical waveguide is formed using this film, a polyimide optical waveguide having a small polarization dependence can be formed. |