JPS58188330A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To enhance the corrosion resistance of the magnetic layer of a magnetic recording medium at high humidity and to prevent the deterioration of the electromagnetic conversion characteristics by forming a magnetic metallic thin film contg. O on a nonmagnetic substrate as the magnetic layer and by sticking a corrosion inhibitor contg. condensed phosphate as a principal component on the film. CONSTITUTION:A magnetic layer contg. 3-45% O is formed on a nonmagnetic substrate by depositing Fe, Ni, Co or an alloy thereof in an O2 atmosphere by vacuum deposition or other method. The layer is coated with a corrosion inhibitor contg. condensed phosphate such as orthophosphate or polyphosphate as a principal component or further contg. a small amount of PVA, CMC or chromic acid by 0.5-500mg per 1m<2> of the resulting magnetic recording medium. Thus, the corrosion of the magnetic layer is prevented even in a high humidity environment whose temp. is considerably changed to cause dew condensation.

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 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 0.06 Because it is small at ~0.5 μm, it is easy to corrode the surface if left in high humidity, especially in an environment where temperature changes are large and condensation occurs, and if this corrosion progresses to a certain extent, it will affect the electromagnetic conversion characteristics. exerts
It also deteriorates practical characteristics such as head touch and 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 it adheres or adsorbs to a few particle layers. There was a need for a rust preventive agent that was sufficiently effective. F
Ferromagnetic thin films that are mainly made of E, Ni, Co, or their alloys and contain oxygen have higher coercive force and superior corrosion resistance than thin films made of pure metals, but they do not contain oxygen. Because it is partially oxidized, the material that exhibits the rust preventive effect - the rust preventive - also contains Fe,
Known anti-rust agents used for bulk metals such as Co and Ni are not necessarily suitable, and when 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 substance containing condensed phosphate 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 Cζ in which a ferromagnetic metal thin film containing oxygen is formed on a non-magnetic substrate, in which a rust preventive agent containing condensed phosphate as a main component is applied to the ferromagnetic metal thin film. It is characterized by being attached.

Polyester film is used as a non-magnetic substrate.

Plastic films such as Bolimide film.

Gold plates such as aluminum plates, stainless steel plates, and inorganic plates such as glass plates are used, and evaporation is performed on these plates directly or through a nonmagnetic thin film layer in a vacuum in the presence of a trace amount of oxygen gas. 0.05mm thick made of diagonal or vertical columnar crystals by methods such as , sputtering, ion blating, etc.
~0, 6 μm Go, Fe.

Fe-Ni, Co-Ni, Fe-Co, Fe-N
Mainly composed of i-Co, etc., with an atomic ratio of oxygen to magnetic metal of 3
A rust preventive agent containing condensed phosphate as a main component is applied to a single-layer or multi-layer ferromagnetic thin film containing ~46%.

The condensed phosphates in the present invention include orthophosphates, polyphosphates, tetrapolyphosphates, metaphosphates, cyclic metaphosphates, long-chain crystalline metaphosphates, ultraphosphates, and the like.

The rust preventive agent in the present invention is mainly composed of these alone or a mixture of two or more of them, and contains at least 80% of these.) If necessary, organic compounds other than condensed phosphates, such as polyvinyl A small amount of alcohol, carboxymethyl cellulose, or an inorganic compound such as chromic acid or molybdic acid is 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 density is 0.5 to 6o0m per 1m of the magnetic recording medium, about 9.Specifically, the presence of the rust preventive agent can be carried out by itself or by a substance that has the ability to form a film such as a polymeric compound. If necessary, dilute it with a solvent and apply it to the surface of the ferromagnetic thin film in a mixed state, or apply rust preventive vapor to the surface of the ferromagnetic thin film.Furthermore, if the magnetic recording medium is tape-shaped, A known L stage can be used, such as a method in which the tape is placed on the back side and transferred to the surface of the ferromagnetic thin film when the tape is wound.In addition, in addition to the rust preventive agent, ordinary lubricants and antistatic agents can be used. It is also possible to use additives such as agents.

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

A polyester film with a thickness of 10 μm was melted by electron beam heating by introducing oxygen gas at a vacuum level of 5 x 10 Torr along the circumferential surface of the P can at a rate of 3 Q/M. Ni containing 20w
t%) was continuously obliquely deposited (low incident angle component 300 or more) to form an oxygen-containing CoNi ferromagnetic thin film with a thickness of 1oOo'A on the film (Sample A), and under similar conditions as in Section L. A CoNi ferromagnetic thin film containing no oxygen was prepared at a vacuum level of 5×10 −6 Torr without introducing oxygen gas (sample B). As a result of measuring oxygen acid in the film mainly using Auger electron spectroscopy, it was found that the average oxygen content in the film of sample A was 10% at the atomic ratio of Co to Ni (-1-x 1ω)Co+N1. , that of sample B was less than 1 inch. A rust preventive agent containing condensed phosphate as the main component was dissolved in a solvent of water, ethyl alcohol, acetone, etc., and then applied and dried on the surface of these samples (10 to 1 o om for clear coating, 9/8
It was adjusted to be m. ) and then 60℃, 90%R
-H, the specimen was left in an atmosphere, during which time it was periodically taken out and observed under a microscope to examine the state of rust formation. The results are shown in the table.

As is clear from the table, the rust preventive agent containing condensed phosphate as a main component had a great rust preventive effect on the CoNi thin film containing oxygen. This effect is due to the oxygen content of 3 to 46 modulus (1') CoN
The same was true for the i thin film (N i 10-65 wt %), and it was also similar for the Co thin film, FeNi thin film, Fe-Co thin film, etc.

In addition, for untreated products without rust prevention, both samples A and B are
It occurred within one week.

As explained in F- below, 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 non-magnetic substrate-1-, and a rust preventive agent containing condensed phosphate as a component is adhered to the ferromagnetic metal thin film. .