| abstract |
An aromatic polyimide film containing very fine particles of an inert inorganic material having an average particle diameter of 40 to 1,000 angstroms in an amount of 0.02 to 6.0 wt. %, wherein a surface of the film is provided with extremely small sized protrusions having a maximum height of 50 to 500 angstroms and an average diameter of 50 to 2,000 angstroms, the number of protrusions is in the range of 2x105 to 1x108/mm2, and the number of protrusions having a diameter of not less than 1.5 times as much as the average diameter is not more than 5% of the total number of the protrusions. This polyimide film is suitably employable as a support of a magnetic recording medium. |