| 摘要 |
PURPOSE:To obtain a base film for a magnetic tape having excellent runnability, scratching resistance, S/N ratio and drop-out characteristic by combining a swellable inorg. laminar silicate with a prescribed amt. of a water soluble resin and forming a uniformly and finely dispersed layer of the silicate on the surface of a polyester film. CONSTITUTION:The layer which is obtd. from a mixture composed of the swellable inorg. laminar silicate and the water soluble resin at 3/10,000-1/10 weight ratio and has <=0.02mum Ra measured by a stylus type surface roughness meter is provided on at least one surface of the polyester film which is a base material. The compsn. essentially consisting of the inorg. laminar silicate, the water soluble resin and solvent is coated on at least one face of the smooth polyester film after uniaxial stretching and the film is stretched in the perpendicular direction after or during drying or is further uniaxially stretched again after the stretching in the perpendicular direction then such film is subjected to a heat treatment. The easily slippable polyester film which is biaxially stretched and has the surface formed with the continuous film having fine projections is thus obtd.
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