Abstract: A biaxially oriented polyester film which has a Young's modulus (YMD) in the film machine direction (YMD) of 6.5 GPa or more and a Young's modulus in the width direction (YTD) of 8.2 to 9.8 GPa and is used as a base film for magnetic recording tapes of linear recording system, and a magnetic recording tape of linear recording system comprising the same as a base film. There are provided a biaxially oriented polyester film which has excellent dimensional stability, especially dimensional stability in the width direction and is suitable for use as a base film for magnetic recording tapes of linear recording system and a magnetic recording tape comprising the same.

Abstract: A polyester film for recording medium, having one major surface thereof provided with a coating layer containing fine particles of 5 to 60 nm diameter and an organic compound, wherein the number of fine surface projections existing on the surface of the coating layer is in the range of 3 million to 100 million/mm2, and the number of surface defects of 120 nm or greater height attributed to foreign matter contained in the film is 30/100 cm2 or less, and wherein the polyester contains a titanium compound substantially not having any particle diameter. Thus, there are provided a magnetic recording tape for digital data recording that can reduce dropouts and excels in durability, and further provided a polyester film that is suitable as a base film thereof.