JPH0239016B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a ferromagnetic metal thin film magnetic recording medium with improved corrosion resistance in high humidity. Fe, Ni,
A magnetic recording medium in which a ferromagnetic thin film mainly composed of Co or an alloy thereof and containing oxygen is formed is suitable for high-density recording such as video signal recording, but the thickness of the ferromagnetic metal thin film is 0.05 to 0.5 Because it is as small as μm, it is easy for the surface to corrode if it is left in high humidity, especially in an environment where there are large temperature changes and condensation, and if this corrosion progresses to a certain extent, it will affect the electromagnetic conversion characteristics. Deteriorates practical properties such as head touch and wear resistance. When suppressing this corrosion with a rust preventive, there are strict limitations on the thickness of the protective film that can be formed on the surface of the magnetic layer due to spacing loss between the head and the magnetic layer, so only a few molecular layers can be attached or adsorbed. A sufficiently effective rust preventive agent was desired. Ferromagnetic thin films made mainly of Fe, Ni, Co, or their alloys and containing oxygen have higher coercive force than thin films made of these pure metals.
It has excellent corrosion resistance, but because it contains oxygen, that is, it is partially oxidized, it is also a material that exhibits a rust preventive effect (rust preventive agent).
Known anti-rust agents used for bulk metals such as Fe, Co, and Ni are not necessarily suitable, and when applied, they may actually accelerate corrosion. Therefore, it became necessary to find a material compatible with ferromagnetic thin films containing oxygen.
As a result of various studies, the present inventors have found that a rust preventive agent containing an alkylphenol as a main component is suitable as a rust preventive agent for a ferromagnetic thin film containing oxygen. That is, the present invention provides a magnetic recording medium in which a ferromagnetic metal thin film containing oxygen is formed on a non-magnetic substrate, in which a rust preventive agent containing an alkyl substituted monovalent phenol as a main component is applied to the ferromagnetic metal thin film. It is characterized by being attached. As a non-magnetic substrate, polyester film,
Plastic films such as polyimide films,
Metal plates such as aluminum plates and stainless steel plates, inorganic plates such as glass plates, etc. are used, and evaporation or sputtering is performed on these plates directly or through a non-magnetic thin film layer in a vacuum in the presence of a trace amount of oxygen gas. Co, Fe, with a thickness of 0.05 to 0.5 μm, consisting of diagonal or vertical columnar crystals, using methods such as ion plating.
A single-layer or multi-layer ferromagnetic thin film mainly composed of Fe-Ni, Co-Ni, Fe-Co, Fe-Ni-Co, etc., containing 3 to 45% oxygen in atomic ratio to the magnetic metal. Apply a rust preventive agent containing alkylphenol as the main component. The alkylphenol in the present invention refers to an alkyl-substituted monovalent phenol, for example,
o-cresol, m-cresol, p-cresol, o-ethylphenol, m-ethylphenol, p-ethylphenol, 2,3-dimethylphenol, 2,5-methylphenol, 2,6-
Dimethylphenol, 3,4-dimethylphenol, 3,5-dimethylphenol, 2,4,6-
Trimethylphenol, 2,4,5-trimethylphenol, 5-isopropyl-2-methylphenol, 2-isopropyl-5-methylphenol, p-tert-butylphenol, 2,6-di-
tert-butyl-p-cresol, 4,4'-methylenebis-2,6-di-tert-butylphenol,
2,6-dimethyl-4-tert-butylphenol, 2-tert-amyl-4-methylphenol,
Examples include 2-methyl-4,6-di-tert-butylphenol, 2,4,6-tri-tert-butylphenol, and the like. The rust preventive agent in the present invention is mainly composed of these substances alone or a mixture of two or more thereof (containing at least 80%), and optionally contains organic compounds other than alkyl substituted monovalent phenols, such as It contains small amounts of hydroquinones, acetophenones, quinones, etc. These anti-corrosion agents exhibit their effects by being present at least on the surface of the ferromagnetic thin film, if possible inside, or in contact with the interface with the base on which the ferromagnetic thin film is formed. The appropriate amount is about 0.5 to 500 mg per m ² of magnetic recording medium. Specifically, the rust preventive agent is applied on the surface of the ferromagnetic thin film, either by itself or mixed with a film-forming agent such as a polymer compound, diluted with a solvent if necessary. The method is to apply rust preventive vapor to the surface of the ferromagnetic thin film.

【table】

【table】

[Table] As explained above, according to the present invention, corrosion resistance in high humidity can be easily improved.

Claims (1)

[Claims] 1. In a magnetic recording medium in which a ferromagnetic metal thin film containing oxygen is formed on a non-magnetic substrate, a rust preventive agent containing an alkyl substituted monovalent phenol as a main component is attached to the ferromagnetic metal thin film. Features of magnetic recording media.