Stock material or miscellaneous articles – Composite – Of quartz or glass
Patent
1988-10-03
1990-11-06
Thibodeau, Paul J.
Stock material or miscellaneous articles
Composite
Of quartz or glass
427129, 427132, 428457, 428611, 428694, 428702, 428900, G11B 2300
Patent
active
049685643
DESCRIPTION:
BRIEF SUMMARY
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.
THE PRIOR
Magnetic recording media which comprise a non-magnetic substrate having a coating thereon of a kneaded mixture of a magnetic powder, such as of .gamma.-Fe.sub.2 O.sub.3 or Fe and a synthetic resin binder are known. Also known are thin metal film-type magnetic recording media which comprise a substrate having a thin metal magnetic film thereon. Such thin metal film-type magnetic recording media are capable of high density recording. Methods of forming the thin metal magnetic film on the substrate include
(a) a chemical plating method, this being a wet process, and
(b) a sputtering method, an ion plating method or a vacuum evaporation method, this being a 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 thermodynamic 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 and No. Sho 58-134414 to improve the corrosion resistance of a magnetic recording medium by either adding metals, supplying a gas mixture of ozone and oxygen to the magnetic layer portion, or quantitatively setting the number of oxygen atoms.
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 decreased 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 medium of Co-Ni series of metal film type.
SUMMARY OF THE INVENTION
In this invention, a magnetic layer comprising Ni, rare earth element R, oxygen, Co and other inevitable impurities is formed on a non-magnetic substrate, 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 the weight basis, 0-22% Ni, not more 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-magnetic 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 rare earth element R consisting one or more of Y, La, Ce, Pr, Nd, Sm, Gd, Td, and Dy is added in order to improve the magnetic properties and the corrosion resistance of the Co-Ni series metal magnetic layer. If it is added in excess of 13% by weight, the coercive force and the saturation magnetization are decreased and the corrosion resistance as well.
For obtaining the magnetic layer of the above-mentioned composition, one of B, C, Al, Si, Sn, S, Cu, Zn, Fe, T
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.
patent: 4769282 (1988-09-01), Tada et al.
Akihiro Makoto
Oka Kouichi
Sato Takehiko
Tada Junya
Watanabe Tomohisa
Sumitomo Metal Mining Company Limited
Thibodeau Paul J.
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