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US 5,047,278 AGranted
Polyester film and magnetic recording medium
AssigneeToray Industries, Inc.
InventorsMasaaki Ono, Takao Izasa, Kazuo Okabe
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AssigneeToray Industries, Inc.
InventorsMasaaki Ono, Takao Izasa, Kazuo Okabe
Estimating the term…
A polyester which is prepared by using a germanium compound as the polymerization catalyst, in which the Young's modulus E.sub.MD in the machine direction and the Young's modulus E.sub.TD in the transverse direction satisfy the requirements of E.sub.MD .gtoreq.350 kg/mm.sup.2, E.sub.TD .gtoreq.350 km/mm.sup.2 and E.sub.MD .times.E.sub.TD .gtoreq.250,000 kg.sup.2 /mm.sup.4, the refractive index n.sub.ZD in the thickness direction satisfies the requirement of 1.480.gtoreq.n.sub.ZD .gtoreq.1.492, and the maximum roughness Rt of at least one surface satisfies the requirement of Rt.gtoreq.100 nm, is valuable as a base film for a magnetic recording medium. A laminate structure of a polyester layer A and a polyester layer B is also used as a base film for a magnetic recording medium, in which the above requirements of E.sub.MD, E.sub.tD and n.sub.ZD are satisified, fine particles are incorporated in the layer B, the outer surface of the layer A satisfies the requirement of Rt .gtoreq.100 nm and Rt of the outer surface of the layer B is in the range of from 30 to 150 nm. A magnetic recording medium having a ferromagnetic metal thin film formed thereon, which is prepared by using this polyester film has a good processability at the preparation and shows a reduced drop-out, and this magnetic recording medium is scratched only to a negligible extent by contact with a magnetic head and does not damage the magnetic head.
A polyester film for forming thereon a ferromagnetic metal thin film for a magnetic recording medium, which is composed of a polyester prepared by using a germanium compound as the polymerization catalyst, wherein the Young's modulus E.sub.MD in the machine direction thereof and the Young's modulus E.sub.TD in the transverse direction thereof satisfy the requirements of E.sub.MD .gtoreq.350 kg/mm.sup.2, E.sub.TD .gtoreq.350 kg/mm.sup.2 and E.sub.MD .times.E.sub.TD .gtoreq.250,000 kg.sup.2 /mm.sup.4, the refractive index n.sub.ZD in the thickness direction thereof satisfies the requirement of 1.480.ltoreq.n.sub.ZD .ltoreq.1.492, and the maximum roughness Rt of one surface of the film is not larger than 100 nm and the maximum roughness Rt of the other surface of the film is in the range of from 30 to 150 nm.
A polyester film for forming thereon a ferromagnetic metal thin film for a magnetic recording medium, which comprises a laminate of layers A and B of polyester formed by using a germanium compound as the polymerization catalyst, wherein Young's modulus E.sub.MD in the machine direction thereof and the Young's modulus E.sub.TD in the transverse direction thereof satisfy the requirements of E.sub.MD .gtoreq.350 kg/mm.sup.2, E.sub.TD .gtoreq.350 kg/mm.sup.2 and E.sub.MD .times.E.sub.TD .gtoreq.250,000 kg.sup.2 /mm.sup.4, the refractive index n.sub.ZD in the thickness direction satisfies the requirement of 1.480.ltoreq.n.sub.ZD .ltoreq.1.492, fine particles are incorporated in the layer B, the maximum roughness of the exposed surface of the layer A which is not in contact with the layer B satisfies the requirement of Rt.ltoreq.100 nm, and the maximum roughness Rt of the exposed surface of the layer B which is not in contact with the layer A is in the range of from 30 to 150 nm.
A magnetic recording medium having a ferromagnetic metal thin film formed thereon, which comprises a polyester film and a thin film comprising at least one ferromagnetic metal selected from the group consisting of iron, cobalt, nickel and alloys thereof, which is formed on one surface of the polyester film, wherein the polyester film is composed of a polyester prepared by using a germanium compound as the polymerization catalyst, in which the Young's modulus E.sub.TD in the transverse direction thereof satisfy the requirements of E.sub.MD .gtoreq.350 kg/mm.sup.2, E.sub.TD .gtoreq.350 kg/mm.sup.2 and E.sub.MD .times.E.sub.TD .gtoreq.250,000 kg.sup.2 /mm.sup.4, the refractive index n.sub.ZD in the thickness direction satisfies the requirement of 1.480.ltoreq.n.sub.ZD .ltoreq.1.492, and the surface of the polyester film on which the thin ferromagnetic metal film is formed has a maximum roughness Rt of not larger than 100 nm and the surface of the polyester film on which the thin ferromagnetic metal film is not formed has a maximum roughness Rt of from 30 to 150 nm.
A magnetic recording medium having a ferromagnetic metal thin film formed thereon, which comprises a polyester film and a thin film comprising at least one ferromagnetic metal selected from the group consisting of iron, cobalt, nickel and alloys thereof, which is formed on one surface of the polyester film, wherein the polyester film comprises a laminate of layers A and B of a polyester formed by using a germanium compound as the polymerization catalyst, wherein Young's modulus E.sub.MD in the machine direction thereof and the Young's modulus E.sub.TD in the transverse direction thereof satisfy the requirements of E.sub.MD .gtoreq.350 kg/mm.sup.2, E.sub.TD .gtoreq.350 kg/mm.sup.2 and E.sub.MD .times.E.sub.TD .gtoreq.250,000 kg.sup.2 /mm.sup.4, the refractive index n.sub.ZD in the thickness direction satisfies the requirement of 1.480.ltoreq.n.sub.ZD .ltoreq.1.492, fine particles are incorporated in the layer B, and the surface of the layer A on which the thin ferromagnetic metal thin film is formed has a maximum roughness Rt of not larger than 100 nm and the exposed surface of the layer B which is not in contact with the layer A has a maximum roughness Rt of from 30 to 150 nm;
Dependencies are inferred from the claim text.