| 摘要 |
PROBLEM TO BE SOLVED: To prepare a polyester film with an excellent straight tearing property, and a packaging bag made therefrom, having an excellent tear opening property. SOLUTION: This is a biaxially oriented polyester film manufactured by use of a raw material which is prepd. by blending a polybutylene terephthalate (modified PBT) comprising 5-20 wt.% of a polytetramethylene glycol unit having a mol.wt. of 600-4,00, and a polyethylene terephthalate(PET) at a PET/modified PBT ratio of 70/30-95/5 (wt.ratio), the modified PBT being dispersed in a shape of long-island-in-the-sea along the film longitudinal direction in the PET, and satisfying the formulae: 10<=L/D<=500 and 5<=N<=20 wherein L (μm) is an average length value, along the film longitudinal direction, of the cross-sectional views of the modified PBT dispersed particles observed at the film longitudinal section, D (μm) is an average length value, along the film transverse direction, of the cross-sectional views of the modified PBT dispersed particles observed at the film transverse section, and N (no./μm<2> ) is a no. of the modified PBT dispersed particles observed at the film transverse section. |
