JPS58222440A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the corrosion resistance of a magnetic recording medium, by sticking a rust preventive agent consisting essentially of a thiourea compd. on a thin film of a ferromagnetic metal contg. oxygen. CONSTITUTION:A ferromagnetic thin film consisting essentialy of Co, Fe., etc. composed of a diagonal or perpendicular columnar crystal and contg. 3-45% oygen in atom ratio with the magnetic metal is formed in a single layer or multiple layers on a non-magnetic substrate in a vacuum where a a slight amt. of gaseous oxygen exists by a method such as vapor deposition, sputtering or the like, whereafter a rust preventive agent consisting essentially of a thiourea compd. is stuck on the surface thereof. Such rust preventive agent is made to exist at last on the surface of the ferromanetic thin film and, if possible, in the inside thereof, or in the state of contacting with the boundary to the base on which the ferromagnetic thin film is formed in order to provide the effect thereof. The adequate amt. thereof is about 0.5-500mg for each 1m<2> of the magnetic recording medium.

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 polynisder or polyimide, or a non-magnetic material such as an aluminum plate or a glass plate, by vapor deposition, ion predinder, sputtering, etc. in a vacuum.

A magnetic recording medium in which a ferromagnetic thin film containing oxygen and mainly composed of GO or an alloy thereof is formed is suitable for high-density recording such as video signal recording. Because the diameter of the small diameter is 0.6 to 0.5 μm, if it is left in high humidity, especially in an environment where there are large temperature changes and condensation occurs, corrosion will easily occur on the surface, and if the corrosion progresses, electromagnetic conversion affect the characteristics,
However, it still deteriorates practical properties such as wear resistance.

When suppressing this corrosion with a rust preventive agent, 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 adhesion or adsorption of several molecular layers is required. There was a need for a rust preventive agent that was sufficiently effective. F
ferromagnetic thin film mainly composed of Ni, Go, or their alloys and containing oxygen: It has higher coercive force and excellent corrosion resistance than thin films made of these pure metals, but it does not contain oxygen. In other words, since it is partially oxidized, it is not necessarily the case that known materials used for bulk metals such as Fe, Go, and Ni are suitable for materials that exhibit a rust-preventing effect (rust inhibitors). No, when we actually apply these anti-corrosion agents, they may actually promote corrosion, so we had to find a new one that was compatible with ferromagnetic thin films containing oxygen. As a result of various studies, the present inventors have found that a substance containing a thiourea-based compound as a main 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 ferromagnetic metal thin film containing oxygen is formed on a non-magnetic substrate, in which a rust preventive agent containing a thiourea-based compound as a main component is added to the ferromagnetic metal thin film. It is characterized by:

Polyester film is used as a non-magnetic substrate.

Plastic films such as polyimide filters.

Metal plates such as aluminum plates and stainless steel plates, inorganic plates such as glass plates, etc. are used, and evaporation is performed on these plates either directly or through a non-magnetic thin film layer in a vacuum in the presence of a small amount of oxygen gas. Made of diagonal or vertical columnar crystals with a thickness of 0.05~ by sputtering, ion blasting, etc.
05 μm Go.

Fe, Fe-Ni, Co-Ni, Fe-Go,
A ferromagnetic thin film consisting mainly of 11':su□ such as Fe-N1-Go and containing oxygen in an atomic ratio of 3 to 46 to the magnetic metal is formed, and a thiourea-based compound is used as the main component. Apply a rust inhibitor as an ingredient.

The thiourea compounds in the present invention include thiourea, N-
Methyl-thiourea, N,N'-dimethyl-thiourea,
N, N, N'-)limethyl-thiourea, N.

Examples include N, N', N'-tetramethyl-thiourea, N-acetylthiourea 2, and the like.

The rust preventive agent in the present invention is mainly composed of a medium or a mixture of two or more of these compounds, preferably containing at least 80q6 or more). If necessary, organic compounds other than thiourea compounds, For example, naphthols, hydroquinones, acetophenones, quinones, etc. are added in small quantities.

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 magnetic recording medium - Bm2
The culm degree is 0.5 to 50 omg. Specific information 8
The rust preventive agent can be applied by itself or mixed with a film-forming agent such as a polymer compound, diluted with a solvent if necessary, and applied to the surface of the ferromagnetic thin film. A method in which vapor is applied to the surface of a ferromagnetic thin film, and a method in which if the magnetic recording medium is in the form of a tape, it is placed on the back side of the magnetic recording medium so that it is transferred to the surface of the ferromagnetic thin film when the tape is rolled up and twisted. , etc. can be used. In addition, along with rust inhibitors, regular lubricants,
It is also possible to use additives such as antistatic agents.

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

A polyester film with a thickness of 10 μm was placed on the circumferential surface of a cylindrical can, and oxygen gas was introduced at a rate of 0.317 fnrrt under a vacuum degree of 5 20w
t%) was continuously obliquely deposited (cutting the low incident angle component below 30%) to form an oxygen-containing CoNi ferromagnetic thin film with a thickness of 1000A on Filno soil (Sample A), -F
A sample B) 1 was prepared in which a CoNi ferromagnetic thin film containing no oxygen was formed under conditions similar to those described above, at a vacuum degree of 5×1° Torr, and without introducing oxygen gas. As a result of measuring the oxygen acid in the film mainly using Auger electron spectroscopy, it was found that the average amount of oxygen in the film of the sample was the same as the atomic ratio of Go to Ni (7
X100) Go+Nl was 10%, and that of sample B was 1% or less. Apply a rust preventive agent mainly composed of thiourea compounds to the surfaces of these samples using ethyl alcohol and acetone.

Dissolve in toluene, etc., apply and dry (coating amount is 1° to 1
It was adjusted to oo mg/m'. ) After that, it was left in an atmosphere at 50°C and 90% LH, and during that period, it was taken out periodically 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 a thiourea compound as a main component had a great rust preventive effect on the CoNi thin film containing oxygen. This effect is due to the fact that CoNi with an oxygen content of 3-46%
The same is true for thin films (NiIQ ~55 wt%), and CO
It was similar in thin films, FeNi thin films, Fe-co thin films, etc.

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 characterized in that a ferromagnetic metal thin film containing oxygen is formed on a nonmagnetic substrate, and a rust preventive agent containing a thiourea-based compound as a main component is applied to the ferromagnetic metal thin film.