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Abstract

The present invention relates to aromatic polyamide film which is characterized in that on at least one face thereof the number of projections of height at least 20 nm but less than 50 nm is from 10.sup.3 to 10.sup.8 per mm.sup.2, and the number of projections of height at least 50 nm but less than 100 nm is from 0 to 3.times.10.sup.4 per mm.sup.2. Further, the present invention also offers a method of producing an aromatic polyamide film which is characterized in that, in a method of producing aromatic polyamide film from a solution obtained by adding to an aromatic polyamide solution a particle-containing slurry formed by dispersing particles of particle diameter 10 to 300 nm in a liquid medium of 10 poise or less, such that the amount of said particles added in terms of the aromatic polyamide is 0.005 to 4.5 wt %, the relative standard deviation in the diameters of said particles is no more than 0.8 and, furthermore, there is used a particle-containing slurry where the initial filterability index Q1 of said particle-containing slurry and the filterability index Q2 after the passage of 500 ml of liquid satisfy the following relation. Q2/Q1.gtoreq.0.3 While the film of the present invention is also ideal for use as flexible printed substrates, capacitors and printer ribbons, etc, since it is possible to realise extremely high levels of both output characteristics and durability, it is especially suitable for magnetic recording media, in particular for computer external memory and digital video tape where high density and high precision are demanded.

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First Claim