| 摘要 |
PURPOSE:To obtain a film, excellent in the accuracy of surface flatness and high in strength as well as Young's modulus, by using a belt or a drum, made of tantalum, as the supporting surface of the film. CONSTITUTION:An endless belt or a drum is employed as the supporting surface of a film. A continuous homogeneous film can not be obtained by using a sheet material such as a glass sheet or the like and its use is not preferable. The supporting surface or at least a surface, on which dope is cast, in necessary to be made of taltalum and when a metal, such as stainless steel, Hastelloy alloy, titanium or the like except the taltalum, can not obtain the effect of this invention. Iron, aluminum or copper is not suitable from the view point of anticorrosion against sulfuric acid. The supporting surface of taltalum is preferable to be polished to a mirror surface and the mirror surface should be 0.2S or less in Rmax concretely and, more preferably, it should be finished so as to be 0.1S or less. The film, obtained in this process, is provided with an excellent mechanical property shown by a high strength and a high Young's modulus, which can not be found in a film sold in market and, further, the surface accuracy thereof is excellent. |
