Toray Industries, Inc.

Yukari Nakamori

Takuji Higashioji

Iwao Okazaki

Tetsuya Tsunekawa

Masato Horie

Akira Kubota

Shozi Nakajima

Masaru Suzuki

Koichi Abe

Masatoshi Aoyama

Masahiro Kimura

Minoru Yoshida

Jun Sakamoto

Makoto Sato

Hiroaki Watanabe

Katsuya Okamoto

Shoji Nakajima

Hidehito Minamizawa

Hideto Mitsuoka

Masaaki Kotoura

Tadamasa Suzuki

Hiroyuki Tanaka

Kenichi Eto

Shinya Kawahara

Yuri Shirakawa

A biaxially oriented thermoplastic resin film has at least one surface of which has protrusions each having a height of 1 nm or more and less than 2 nm at a density of 1&#xd7;10to 1&#xd7;10protrusions per mm. The thermoplastic resin film is capable of suppressing generation of coarse protrusions and contaminants, and defects in a processing process while having slipperiness.

Biaxially oriented thermoplastic resin film

A biaxially orientated polyester film has a P/Vratio of 0.3 to 1.2, Pand Vrepresenting the average diameter of the convex portions and the average diameter of the concave portions, respectively, that are defined on the basis of a slice level with a height of 0 nm (reference plane) in a roughness curve determined for at least one surface using a three dimensional surface roughness meter, and the convex portions accounting for an area ratio of 30% to 51% of the reference plane. The biaxially oriented polyester film is excellent in travelling property, slitting property, and dimensional stability, and serves, when used for magnetic recording medium production, to provide a high density magnetic recording medium having a smooth magnetic layer, suffering little dimensional change due to variations in environmental parameters such as temperature and humidity or due to storage, and having good electromagnetic conversion characteristics with little dropout.

Biaxially oriented polyester film

[Problem to be solved] To provide a biaxially oriented polyester film, which suffers only small dimensional changes due to changes in environmental temperature and humidity and due to storage, ensures low error rates, and can little abrade the magnetic head and the magnetic tape, when used as a base film of a magnetic recording medium, and which can be used to provide a high density magnetic recording medium excellent in running durability. [Solution] A biaxially oriented polyester film having an islands-in-sea structure, an average island domain size of 30 to 200 nm, and a coefficient of hygroscopic expansion of 0 to 6.0 ppm/% RH at least either in the machine direction or in the transverse direction of the film.

Biaxially oriented polyester film and magnetic recording medium

A magnetic recording medium substrate has a polyester film having metallic oxide-containing layers (layers M) formed on both the surfaces, one layer on each surface, the layers M having a thickness of 50 to 200 nm each, characterized in that the magnetic recording medium substrate has a total light transmittance of 0 to 75% and a surface resistivity of 1&#xd7;10to 1&#xd7;10&#x3a9; on each surface.

Support for magnetic recording medium, and magnetic recording medium

The present invention provides a polyester film particularly useful as a base film for a magnetic recording medium such as cassette-type magnetic tape of a digital recording mode and a production process thereof. The polyester film is produced by irradiating UV light onto a surface of a film in a non-stretched stage or a stage prior to the completion of stretching to form fine protrusions on the surface. The fine protrusions on the film surface are specified by the ratio of 10-point average roughness Rz to center line average roughness Ra (Rz/Ra) on the surface (less than 20), the difference in concentration of carboxyl groups between the surface layer part and the inside of the film, and the number of fine protrusions.

Polyester film and method for producing the same

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.

A biaxially-oriented polyester film includes at least two layers and at least one outermost layer is composed of a polyester having a rigid amorphous content of about 10 to 55%. The biaxially-oriented polyester film has a longitudinal Young's modulus of at least about 4.5 GPa. The biaxially-oriented polyester film is suitable for high-density magnetic recording media, such as digital video tapes and high-density data recording tapes.

Biaxially-oriented polyester film

Polyester composition and biaxially oriented polyester film containing

Disclosed is a biaxially oriented film and a laminated film containing specified organic particles at a content of 0.001 to 20% by weight. The strength when deformed by 10% (S.sub.10) of the organic particles is in the range of 3 to 30 kgf/mm.sup.2, the thermal decomposition temperature for causing 10% loss in weight thereof is not lower than 350.degree. C. The weight average diameter thereof is in the range of 0.005 to 5 .mu.m. Since the organic particles have a good affinity with the matrix resin of the film and a good thermal resistance and the hardness of the particles is appropriate, desired protrusions hardly chipped and having an appropriate hardness for hardly scratching a magnetic surface can be formed on a film surface easily and uniformly. Therefore, a film excellent in abrasion resistance and scratch resistance at a high running speed and excellent in running durability can be obtained, which is useful particularly as a base film of a magnetic tape.

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Otsu, Japan

Yukari Nakamori