POLYIMIDE FILM FOR RECORDING MEDIUM AND ITS PRODUCTION

摘要

PURPOSE:To produce continuously the title film having one surface of a high slidability and another surface of a high smoothness by extruding two aromatic polyamic acid solutions through a die for two-layer extrusion and forming a film by the polymer solution casting process. CONSTITUTION:A first aromatic polyamic acid solution containing a fine inorganic filler and a second aromatic polyamic acid solution freed of an inorganic filler are simultaneously fed to an extrusion mechanism having a die for two- layer extrusion and extruded from the holes of the die into two-layer thin films of the solutions over a smooth support, and a thin film formed on the support is dried to form a self-supporting film. This film is peeled from the support and heat-treated. The title film which has one surface having many fine protrusions and has a coefficient of static friction of 0.2-0.6 and another surface being smooth, freed of an inorganic filler and having an average surface roughness Ra<=20Angstrom .