| 摘要 |
PURPOSE:To obtain a polyester film having excellent magnetic disk characteristics by incorporating fine silica particles having prescribed characteristics at a prescribed ratio to polyester which contains terephthalic acid as an essential acid component and contains ethylene glycol as an essential glycol component. CONSTITUTION:The fine silica particles which have 0.01-3.0mum average particle size and simultaneously satisfy the conditions expressed by the equation I and the equation II are incorporated at 0.01-5.0pts.wt. into 100pts.wt. polyester which contains the terephthalic acid as the essential acid component and contains the ethylene glycol as the essential glycol component. In the equation, phiV=V/D<2>, where V is the volume of the particle (mum<3>) and D is the max. diameter (mum) in the projection plane of the particle. The oriented polyester film for magnetic disks contg. the fine spherical silica particles which have an extremely steep grain size distribution, do not contain coarse particles, have excellent dispersibility in the media consisting of ethylene glycol or the polyester, have the extremely less coarse projections when made into the film, provide fine and uniform surface roughness, are easily slipperable and have excellent wear resistance is thereby obtd. |
