Polyester film and magnetic recording medium using the same

1. Field of the Invention The present invention provides a polyester film, which is composed of a polyester resin and a polyimide resin, having superior oligomer-restraining property and dimensional stability. This polyester film also has improved surface conditions, that is, has a reduced number of projections on the surface, and hence, the polyester film shows superior electromagnetic conversion characteristics when used for magnetic recording media. In particular, this polyester film is effectively used for high-density magnetic recording media. This film is composed of a polyester resin and a thermoplastic resin other than a polyester resin, and has a number H1 of coarse projections 0.28 m or more in height of 0 to 100/100 cmon at least one surface of the polyester film and a number H2 of coarse projections 0.56 m or more in height of 0 to 10/100 cmon the same surface.