1. US20070160818 - Biaxially stretched polyester film

The present invention relates to (1) a biaxially stretched polyester film comprising a polyester layer (layer A) which comprises butylene terephthalate units and has a melting point of not higher than 240° C., said biaxially stretched polyester film satisfying such properties that an edge tear resistance in longitudinal direction is smaller than an edge tear resistance in width direction and the edge tear resistances in each of longitudinal and width directions are not more than 40N; (2) a biaxially stretched polyester film having a crystallization temperature (Tc) of not lower than 125° C. and edge tear resistances of not more than 80N in each of longitudinal and width directions; and (3) a biaxially stretched polyester film comprising a polyester layer (layer A) comprising butylene terephthalate units and polyester layers (layer B) which are laminated on the both surfaces of the layer A and has a melting point higher 10° C. or more, than the melting point of the layer A, said biaxially stretched polyester film satisfying such properties that edge tear resistances in each of longitudinal and width directions are not more than 80N and the tensile break elongation is not more than 50%. The said biaxially stretched polyester films are excellent in film-forming stability, can be suitably used as packaging materials instead of the presently used packaging materials such as the cellophane, moisture-proof cellophane and K-coat cellophane, can be used even though having a laminate structure of only a base film and a sealant layer, and also can exhibits a good hand cut-off property.