ARAMID FILM AND ITS USE, METHOD OF MANUFACTURING THE SAME, DETECTION OF PINHOLES IN THE FILM, AND DEVICE FOR THE DETECTION

摘要

A thin aramid film used as a base for a magnetic tape and other products, which has an average thickness of 1-9 mu m and contains at most 20 pinholes/1000 m<2> detected by an electric current flowing under the following voltage applied between both sides of the film: voltage for detection (V) = 20 x (average thickness of film in mu m). The film is made by the film forming process comprising casting an aramid resin solution from a die into an atmosphere with a cleanliness of JIS Class 6 or lower and wet-processing the cast aramid resin at a solvent removal rate of 3x01<-5> g/sec. mu m.cm<2> or less to solidify the film. The obtained aramid film is inspected continuously for at least 500 m<2> with an optical pinhole detector and an electric pinhole detector. The pinhole positions in the longitudinal and lateral directions can be found by calculation and output, as required.