Toray Industries, Inc.

Iwao Okazaki

Koichi Abe

Yukari Nakamori

Shoji Nakajima

Hidehito Minamizawa

Masaru Suzuki

Masatoshi Aoyama

Keisuke Ohshima

Shozi Nakajima

Tohru Miyake

Masahiro Kimura

Minoru Yoshida

Jun Sakamoto

Katsuya Okamoto

Satoru Nishino

Takeo Fukuyama

Hiroyuki Tanaka

Akira Kubota

Kiyohiko Ito

Yuri Shirakawa

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

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

Disclosed is a biaxially oriented, laminated polyester film having a lamination structure with at least two layers. At least one of the outermost layers of the film is a thin laminated layer A having a thickness of not more than 3 .mu.m. In the layer A, internally formed particles and specified agglomerated particles or mono-dispersed particles are present, or the mono-dispersed particles are present at a very small content. When the polyester film is used as a base film for magnetic recording media, the abrasion resistance of the film surface at a high speed can be greatly increased.

Biaxially oriented, laminated 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.

Biaxially oriented film comprising organic particles

Disclosed is a biaxially oriented laminated film comprising a film layer B whose major component is a thermoplastic resin B.sub.r, a thin film layer A laminated on at least one surface of the film layer B and whose major components are a thermoplastic resin A.sub.r and particles with a specified mean diameter contained therein at a specified content, and a skin layer C laminated on at least one surface of the laminated film layer A and film layer B and having a thickness of 1-300 nm. The particles form the desired protrusions on the film surface and the skin layer C can have various properties such as a good adhesive property with a magnetic layer, a good adhesive property with an ink or a good antistatic property without injuring the good scratch resistance, chipping resistance, chromatic S/N, etc., achieved by the desired protrusions formed by the particles.

Biaxially oriented laminated film

Disclosed is a biaxially oriented laminated film having at least three layers which has excellent abrasion resistance and electromagnetic conversion property when the film is used as the base film of a magnetic recording media. The biaxially oriented laminated film comprises at least one outermost layer containing particles A, the particle density ratio at surface layer of the particles A is not less than 0.01, and the mean primary particle size D of the particles A and the thickness T of the outermost layer containing the particles A satisfies the equation; D.ltoreq.T.ltoreq.200D.

Biaxially oriented laminated film comprising particles in a specific

A magnetic recording medium with excellent S/N ratio and durability is disclosed. The magnetic recording medium comprises a substrate film and a magnetic layer formed on at least one surface of the substrate film. The maximum depth of depressiones in the surface of the magnetic layer being larger than maximum height of peaks on the surface of the magnetic layer.

Magnetic recording medium

Disclosed is a biaxially oriented laminated film with excellent scratch resistance and friction property, as well as excellent dubbing resistance when used as a base film of magnetic recording media. The biaxially oriented laminated film comprises a first layer containing a first thermoplastic resin as a major constituent; and a second layer containing a second thermoplastic resin as a major constituent, which is formed on at least one surface of the first layer. The second layer contains inert particles with an average diameter of 0.1 to 10 times the thickness of the second layer, and the content of the inert particles in the second layer is 0.5-50% by weight. The thickness of the second layer is 0.005-3 .mu.m.

A biaxially oriented polyester film suited as a substrate for magnetic recording media. The film comprises a polyester and inert particles and has at least one surface with protrusions formed by the existence of the inert particles. The surface has a parameter of surface topography .sqroot.(.beta./.sigma.) of 0.1 to 0.7. The average distance between adjacent protrusions is not more than 20 um and the coefficient of friction of the surface and the parameter of surface topography satisfies the following equations (1) and (2): ##EQU1## wherein y is the coefficient of friction, .beta. is mean flatness of protrusions and .sigma. is standard deviation of height distribution of protrusions.

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Kyoto, Japan

Iwao Okazaki