Biaxially stretched polyester film

摘要

The present invention relates to a biaxially stretched polyester film comprising a polyester layer A which comprises polybutylene terephthalate and at least one of a copolyester and an amorphous polyester, said biaxially stretched polyester film satisfying any one of the following requirements: (1) the polyester layer A exhibiting one melting point as measured by temperature-rise DSC method, and the polyester film having an edge tear resistance of not more than 100 N in each of longitudinal and width directions thereof; and (2) an average number of uncompatilized polybutylene terephthalate masses having a maximum length of not less than 1μm which are present in a section of the layer A is not more than 1.0 per 100μm2 of the section of the layer A, and the polyester film having an edge tear resistance of not more than 100 N in each of longitudinal and width directions thereof.