Magnetic recording medium

Details Magnetic recording medium Magnetic recording medium

1987-02-20

1988-09-06

Lesmes, George F.

Stock material or miscellaneous articles

Web or sheet containing structurally defined element or...

Physical dimension specified

428457, 428694, 428702, 428900, H01F 1016

Patent

active

047692820

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

1. Technical Field
This invention concerns a magnetic recording medium and, particularly, a Co--Ni series magnetic recording film which includes specific rare earth elements that improve its magnetic properties and its corrosion resistance.
2. The Prior Art
Magnetic recording media are normally formed kneading magnetic powder, such as of .gamma.--Fe.sub.2 O.sub.3 or Fe, with a synthetic resin binder and then coating the product on a non-magnetizable substrate.
A magnetic recording medium capable of higher density recording than the coated-type magnetic recording medium has been also developed in which a thin metal magnetic film is formed on a substrate. Methods of forming the thin metal magnetic film on a substrate include: method, these being dry processes.
It has generally been considered that a dry process, (b), can provide a favorable magnetic recording medium as compared with the wet process, (a), in view of the primary treatment applied to the substrate and the homogeneity of the magnetic layer in the longitudinal direction and the lateral direction.
However, the thin metal film type magnetic recording medium formed by the dry process has a much lower thermohydrodynamic stability and more pores as compared with oxide magnetic powder, and it tends to be readily corroded in air, thus causing a reduction in its performance.
Many attempts have been made to improve the corrosion resistance without reducing the magnetic properties of the magnetic recording medium. For example, it has been disclosed in Japanese Patent Laid Open No. Sho 56-15014, No. Sho 57-196507 No. Sho 58-134414 to improve the corrosion resistance of a magnetic recording medium by either incorporating metal additives, supplying a gas mixture of ozone and oxygen to the magnetic layer-forming portion, or quantitatively setting the content of oxygen atoms incorporated in the magnetic layer.
However, only a slight improvement in the corrosion resistance is achieved by any of the foregoing treatments, and the saturation magnetization or the residual magnetization is descreased depending on the treatment resulting in the reduction in the reproduced signal level of the magnetic recording medium.
The object of this invention is to overcome the foregoing drawbacks in the conventional magnetic recording media and to provide those with improved magnetic properties and corrosion resistance by adding specific rare earth elements to the magnetic recording media of Co--Ni series of metal film type.


SUMMARY OF THE INVENTION

In this invention, a magnetic layer comprising Ni, metal element M, rare earth element R, oxygen and Co is formed on a non-magnetic substrate, the metal element M consisting of one or more of B, Al, Si, P, Ge, Sn, Sb, Se, Te, Pb, Bi, Cu, Ti, V, Cr, Zr, Nb, Mo, W and Ta, and the rare earth element R consisting of one or more of Y, La, Ce, Pr, Nd, Sm, Gd, Tb and Dy, in which the composition of the magnetic layer comprises, on weight basis, 0-22% Ni, 1-8% metal element M, less than 13% rare earth element R, 3-13% oxygen, the balance of Co and inevitable impurities.
This invention will further be explained below starting with an explanation of why the composition of the magnetic layer formed on the non-magnetizable substrate is limited as noted above.
Ni basically has a tendency of reducing the residual magnetization of the magnetic recording medium and has an effect of improving the corrosion resistance of the magnetic layer of metal mainly composed of Co. If it is contained in excess of 22% by weight, the residual magnetization of the magnetic layer is remarkably reduced, thus lowering the reproduced signal level.
The metal element M consisting one or more of B, Al, Si, P, Ge, Sn, Sb, Se, Te, Pb, Bi, Cu, Ti, V, Cr, Zr, Nb, Mo, W and Ta is incorporated in order to stabilize and improve the corrosion resistance of the Co--Ni series metal magnetic layer. If it is less than 1% by weight, no effect is recognized. While on the other hand, if it is contained in excess of 8% by weight, the residual magnetization of the magnetic

REFERENCES:
patent: 4323629 (1982-04-01), Kunieda et al.
patent: 4511635 (1985-04-01), Nagao et al.
patent: 4592948 (1986-06-01), Kohomoto et al.
patent: 4661418 (1987-04-01), Yanai et al.

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