Toray Industries, Inc.

Akira Kubota

Yukari Nakamori

Tetsuya Tsunekawa

Iwao Okazaki

Shoji Nakajima

Shozi Nakajima

Kenichi Eto

Yuri Shirakawa

An object of the present invention is to provide a high-quality biaxially oriented film exhibiting an excellent electromagnetic conversion property, traveling durability, magnetic head traveling performance, etc. as a magnetic recording medium. The object of the present invention is achieved by a biaxially oriented film including a polymer alloy composed of polyester (polymer 1) and a thermoplastic resin (polymer 2) other than the polyester as essential components, wherein micro protrusions having a height of 2 to 50 nm are formed at a density of 1,000,000 to 90,000,000/mmon at least one surface.

Biaxially oriented film having specified micro protrusions

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 &mgr;m or more in height of 0 to 100/100 cm on at least one surface of the polyester film and a number H2 of coarse projections 0.56 &mgr;m or more in height of 0 to 10/100 cm on the same surface.

Polyester film and magnetic recording medium using the same

According to the present invention, a biaxially oriented polyester film is provided which comprises at least one film layer composed predominantly of polypropylene terephthalate and has a heat shrinkage of 0.8% or below after standing at 80&deg; C. for 30 minutes. This film is excellent in wear resistance and hence useful particularly for magnetic recording media.

Biaxially oriented polyester film

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Nara, Japan

Akira Kubota