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

摘要

The present invention discloses a thin aramid film which has an average thickness of from 1 to 9 mu m and 20/1,000 m<2> and less of pinholes, detected by a current flow during the application of a voltage satisfying the formula mentioned below, and which is used as a base material of a magnetic tape: <MATH> In the production of an aramid film by a film-forming method wherein a solution of an aramid resin is cast from a die in an atmosphere having a cleanness of up to JIS class 6, and the cast resin is subjected to wet treatment at a solvent removal rate of 3 x 10<-5> g/sec. mu m.cm<2> and less to form a solidified film, the thin aramid film of the present invention is produced by continuously inspecting the film for pinholes in an area of at least 500 m<2> with an optical pinhole inspection apparatus and a current application type of pinhole detection apparatus. The locations of pinholes in the longitudinal and transverse directions of the film can be calculated and outputted if necessary. <IMAGE>