Dynamic magnetic information storage or retrieval – Record medium – Disk
Reexamination Certificate
1998-11-04
2001-07-31
Miller, Brian E. (Department: 2754)
Dynamic magnetic information storage or retrieval
Record medium
Disk
C360S235400, C428S065100, C428S690000, C428S690000
Reexamination Certificate
active
06268978
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic disk apparatus used for external storage apparatuses of computer systems or the like.
With recent increase in quantity of information, importance of magnetic disk apparatuses as external storage apparatuses is more and more enhanced, and they are always required to have recording capacity of high density.
A magnetic disk apparatus has a magnetic recording medium
1
and a magnetic head
2
(hereinafter referred to as “head”) as main constituent elements and further comprises a rotation controlling mechanism
3
of the magnetic recording medium
1
, a positioning mechanism
4
for the head
2
and a processing circuit
5
for recorded and reproduced signals. At the time of stopping of the magnetic disk apparatus, the head rests on the magnetic recording medium, and, upon starting of the magnetic disk apparatus, moves above the magnetic recording medium at a very small flying height from the magnetic recording medium or in the state of direct or indirect contact with the magnetic recording medium, thereby to carry out recording and reproducing of information.
In general, in a magnetic disk apparatus, the information is recorded in a large number of tracks provided concentrically or spirally on the magnetic recording medium. In order to improve recording density, it becomes necessary to increase information density in the tracks in circumferential direction (linear recording density). The linear recording density depends on characteristics of magnetic film (coercive force, thickness, etc.) of the magnetic recording medium, head characteristics (frequency characteristics, gap length, etc.) and spacing between the magnetic film of the magnetic recording medium and the head. Recently, this spacing between the head and the magnetic recording medium (herein-after referred to as “flying height”) is sharply reduced and is generally 0.05-0.1 &mgr;m. In general magnetic disk apparatuses, it is known that both the magnetic head and the magnetic recording medium are worn in the state of the flying height being very small or in the case of the magnetic recording medium and the head directly or nearly contacting with each other, and this wear causes rupture of information to reduce reliability.
Conventionally, the wear is diminished by forming a film of lubricant such as perfluoro polyether or forming a protective film on the surface of the magnetic head. However, these conventional methods are not satisfactory for the diminishment of the flying height of the future magnetic heads, and further intensive improvement is being attempted.
For example, according to IEEE Transaction on Magnetics, Vol. MAG-23, No.5, pp2386 September, 1987, it is attempted to diminish the frictional force and wear by dispersing spherical fine particles of melamine cyanurate (MCA) in the lubricant on the surface of the magnetic disk medium.
As another method, Advances in Information Storage and Processing Systems ASME, ISPS-Vol.1, pp117, 1995 discloses incorporation and dispersion of a phosphazene ring substituted with fluorinated benzene at a terminal (a spherical molecule or soccer ball-shaped molecule of about 1.2 nm in molecular simulation) in the lubricant film on the disk.
Furthermore, Japan Tribology Society, preliminary lecture collection, 1996-10 (page 205) reports to coat on a magnetic recording medium a spherical lubricant such as a polyester hyperbranch polymer substituted with fluorinated carbon at a terminal.
Moreover, as an example of forming a texture on the magnetic head, Japan Tribology Society, preliminary lecture collection, 1996-5 (page 50) proposes a texture of hexagonal honeycomb structure.
The conventional technique disclosed in the above IEEE Transaction on Magnetics gives no consideration to the texture of a slider surface of the magnetic head, the particle size of MCA and the surface roughness of magnetic disk medium, and this technique suffers from the problem that reliability of magnetic disk apparatus performing recording and reproduction at a small floatation distance cannot be ensured.
The conventional technique disclosed in the above Advances in Information Storage and Processing Systems ASME, ISPS gives no consideration to the roughness of magnetic disk medium and the texture of slider surface of the magnetic head and suffers from the problem that reliability of magnetic disk apparatus performing recording and reproduction at a small floatation distance cannot be ensured.
Furthermore, the conventional technique disclosed in the Japan Tribology Society, preliminary lecture collection, 1996-10 (page 205) uses only a spherical lubricant as a lubricant and does not use as additives to a liquid lubricant, and besides gives no consideration to the roughness of magnetic disk medium and the texture of slider surface of the magnetic head and suffers from the problem that reliability of magnetic disk apparatus performing recording and reproduction at a small floatation distance cannot be ensured.
Moreover, the conventional technique disclosed in Japan Tribology Society, preliminary lecture collection, 1996-5 (page 50) gives no consideration to the optimization of lubricants of the corresponding magnetic disk media and suffers from the problem that reliability of magnetic disk unit performing recording and reproduction at a small floatation distance cannot be ensured.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a magnetic disk apparatus excellent in wear resistance and high in reliability.
For attaining the above object, the magnetic disk apparatus of the present invention has cylindrical or polygonal cylindrical protrusions on at least one of the slider surface of the magnetic head and the surface of the magnetic disk and is provided with a lubricant film on the surface of the magnetic disk, an additive comprising spherical or polyhedral molecules or particles being dispersed in said lubricant film.
Furthermore, for attaining the above object, the magnetic disk apparatus of the present invention has protrusions of honeycomb structure on at least one of the slider surface of the magnetic head and the surface of the magnetic disk and is provided with a lubricant film on the surface of the magnetic disk, an additive comprising spherical or polyhedral molecules or particles being dispersed in said lubricant film.
The additives are preferably carbon, carbon compounds, silicon compounds, phosphorus compounds, etc., and, for example, preferred are those comprising elements of H, C, N, O, F, Si and P. Diameter or maximum diameter of the additives is preferably 0.4-30 nm from the points of the flying height of head, the surface roughness of practical magnetic disk medium and the surface roughness of magnetic head, and is more preferably 0.4-20 nm. If the size of the additives is too large, the flying height of the head increases to cause fluctuation of the flying height at the time of recording and reproduction. If it is too small, they have no meaning as particles to lose the effects of rolling friction and sliding friction. Furthermore, they cause the problem of thermal flying.
The shape of the additives is preferably three-dimensionally spherical or polyhedral. Those of relatively large level of 5-20 nm can be observed by SEM, TEM, etc. As other method for the observation of the shape, the shape of polymeric particles can be presumed by molecular simulation software. In the case of polyhedron, hexahedron or higher polyhedrons are preferred.
These additives may be those which can hardly be chemically activated, and are considered to be lower in catalytic action which accelerates wearing as compared with metallic fine particles and to be smaller in the degree of causing wear depth as compared with metallic fine particles. It is further considered that they have less action to corrode the magnetic disk medium and magnetic head as compared with metallic fine particles.
The additives are added in an amount of preferably 0.5-15 wt %, more preferably 1-10 wt % based on the lubricant.
The protrusions may b
Matsumoto Hiroyuki
Tani Hiroshi
Hitachi , Ltd.
Kenyon & Kenyon
Miller Brian E.
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