| 摘要 |
PURPOSE:To improve the resistances to shaving and scratch of a polyester film by incorporating a fine chromium oxide powder as the lubricant into the film. CONSTITUTION:A polyester resin having an intrinsic viscosity (in o-chlorophenol at 35 deg.C) of 0.4-0.9dl/g is compound with 0.05-1wt.% fine chromium oxide powder having an average particle size of 0.05-0.5mum as the lubricant, if necessary together with 0.01-2.0wt.% inert particles having an average particle size of 0.3-2.0mum and is extruded in the temp. range from the m.p. (Tm deg.C) of the resin to (Tm+70) deg.C to give an unstretched film having an intrinsic viscosity of 0.35-0.9dl/g. The film is stretched monoaxially by 2.5-5.0 times in the temp. range from (Tg-10) deg.C to (Tg+70) deg.C (wherein Tg is the glass transition point of the resin), then stretched in the direction vertical to the foregoing stretching by 2.5-5 times in the temp. range from Tg to (Tg+70) deg.C, and thermally set in the temp. range from (Tg+70) to Tm deg.C. |
