JPS593725A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To prevent the surface corrosion of a magnetic medium by sticking a corrosion inhibitor contg. diketone as a principal component on the ferromagnetic metallic thin film contg. oxygen. CONSTITUTION:A single-layer or multilayered ferromagnetic metallic thin film 0.05-0.5mum thickness is formed on a nonmagnetic substrate by vapor deposition, sputtering or other method in a vacuum where a very small amount of gaseous oxygen is present. The thin film consists of diagonal or vertical prismatic crystals and contains oxygen by 3-45atomic% of the amount of the magnetic metal such as Co, Fe or Fe-Ni. A corrosion inhibitor contg. diketone as a principal component is applied at least on the surface of the film. It is incorporated into the film if possible. Acetylacetone, propionylacetone, butyrylacetone, isobutyrylacetone, caproylacetone, 3-methyl-2,4-pentanedione or the like may be used as the diketone.

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 and Ni are deposited on the surface of a substrate made of a plastic film such as polyester or polyimide, or a non-magnetic material such as an aluminum plate or a glass plate, by vapor deposition, ion blasting, sputtering, etc. in a vacuum.

A magnetic recording medium in which a ferromagnetic thin film made of GO or an alloy thereof and entirely composed of oxygen is suitable for high-density recording such as video signal recording, but the thickness of the ferromagnetic metal thin film is Because it is small at 0.05 to 0.5 μm, it is easy to cause corrosion on the surface if left in high humidity, especially in an environment where temperature changes are large and condensation occurs. Once the corrosion progresses to a certain extent, electromagnetic conversion affect the characteristics,
It also completely deteriorates practical properties such as spacing and abrasion resistance.

When suppressing this corrosion with a rust preventive agent, there are strict limits 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. A sufficiently effective rust preventive agent was desired. F
Ferromagnetic thin films that are mainly made of e, Ni, Go, or their alloys and contain oxygen have higher coercive force and superior corrosion resistance than thin films made of pure metals. A material that exhibits a rust-preventing effect because it is partially oxidized.
However, the known anti-corrosion agents used for rust metals such as Fe, Co, and Ni are not necessarily suitable, and when these anti-rust agents are actually applied, they may actually accelerate corrosion. It became necessary to find a new material that was compatible with ferromagnetic thin films containing oxygen.

As a result of various studies, the present inventors have found that a diketone-based component is suitable as a rust preventive agent for ferromagnetic thin films containing oxygen. That is, the present invention provides a magnetic recording medium in which a magnetic metal thin film containing oxygen is formed on a non-magnetic substrate.
It is characterized by being coated with a rust preventive agent whose main component is diketones.

As a non-magnetic substrate, a plastic film such as polyester film 1 polyimide film is used.

A metal plate such as an aluminum plate, a stainless steel plate, an inorganic plate such as a glass plate, etc. are used, and these plates are coated directly or through a non-magnetic thin film layer in a vacuum in the presence of a trace amount of oxygen gas. Vapor deposition ν Thickness 005 consisting of diagonal or vertical columnar crystals by sputtering, ion blasting, etc.
~o6 μm Go.

Fe, Fe-Ni, Go-Ni, Fe-G
Rust preventive coating containing diketones as the main component on a single or multilayer ferromagnetic thin film made mainly of Fe-N1-Go, etc. and containing 3 to 45% oxygen in atomic ratio to the magnetic metal. apply the agent.

The diketones in the present invention include acetylacetone, propionylacetone, and butyrylacetone.

Isobutyrylacetone 嘗 Caproylacetone, 3-methyl-2,4-pentanedione, 3-methyl-3,4-
Hexanedione, 3-methyl-2,4-hef.

Tandione, dibenzoylmethane, etc.

The rust preventive agent in the present invention is mainly composed of these substances alone or a mixture of two or more thereof, and preferably contains at least 8
o% or more) If necessary, a small amount of organic compounds other than diketones, such as naphthols, hydroquinones, acetophenones, and quinones, are added.

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 1rn' for the magnetic recording medium.
It is about 0.5 to 500 mg per serving. Specifically, the rust preventive agent is mixed with the substance itself or with a film-forming substance such as a polymer compound, diluted with a solvent if necessary, and applied to the surface of the ferromagnetic thin film. Another method is to expose the vapor of a rust preventive agent to the surface of the ferromagnetic thin film.Furthermore, if the magnetic recording medium is in the form of a tape, it is placed on the back side of the magnetic recording medium and when the tape is rolled up and cooled, it is transferred to the surface of the ferromagnetic thin film. Well-known means such as a method of forcing the temperature to rise can be used. It is also possible to use additives such as ordinary lubricants, anti-rusting agents, etc., in addition to the anti-corrosion agents.

Next, embodiments of the present invention will be specifically described.

10μm thick polyester film? A CoNi alloy (Ni content: 20 wt%) was bath-melted by electron beam heating by introducing oxygen gas fo at a rate of 31/mm along the circumferential surface of the cylindrical can at a vacuum level of 6 x 10 Torr.
) was continuously obliquely deposited (cutting the low incident angle component 3σ or less) to form an oxygen-containing CoNi ferromagnetic thin film with a thickness of 1000A on the film (sample) under the same conditions as above at a degree of vacuum of 5x. A CoNi ferromagnetic thin film containing no oxygen was prepared at 10' Torr without introducing oxygen gas (sample B). As a result of measuring the amount of oxygen in the film mainly using Auger electron spectroscopy, it was found that the average amount of oxygen in the film of sample A was determined by the atomic ratio of GO to Ni (Go
+N□×1) is 10%, and that of sample B is 1
% or less. A rust preventive agent containing diketones as a main component is dissolved in ethyl alcohol, acetone, toluene, etc. and dried on the surface of these samples.
It was adjusted to be mg/rn'. ) and then 50℃
, 90 degrees R, H. During this period, the specimens were periodically taken out and observed under a microscope to examine the state of rust formation.

The results are shown in the table below.

As is clear from the table, the rust preventive agent containing diketones as a main component had a great rust preventive effect on the CoNi thin film containing oxygen. This effect is due to the C0Ni thin film with an oxygen content of 3 to 45% (
The same is true for Ni10-55Wt, GO thin film,
Similar results were observed in FeNi thin films, Fe-co thin films, and the like.

In addition, for the untreated products without rust prevention, rust occurred within one week for both Samples A and B.

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

Claims (1)

[Claims] A magnetic recording medium #A, characterized in that a ferromagnetic metal thin film containing oxygen is formed on a nonmagnetic substrate, and a rust preventive agent containing diketones as a main component is adhered to the ferromagnetic metal thin film.