Chemistry: electrical and wave energy – Processes and products – Coating – forming or etching by sputtering
Reexamination Certificate
1995-05-18
2002-04-02
McDonald, Rodney G. (Department: 1755)
Chemistry: electrical and wave energy
Processes and products
Coating, forming or etching by sputtering
C427S131000, C427S532000, C427S533000, C427S535000, C427S539000, C204S192200, C204S192150
Reexamination Certificate
active
06365012
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic recording medium for use in a magnetic disk apparatus for information recording and a method of manufacturing the same.
2. Description of the Prior Art
As a magnetic recording medium for performing high-density recording such as a hard magnetic disk, a metal magnetic thin-film medium formed by a coating method such as a plating method, a sputtering method, or a deposition method is used.
Recording of information in a hard magnetic disk or reproduction of recorded information therefrom is performed by a CSS (Contact Start/Stop) system. In this system, the disk is rotated at a predetermined speed to form a thin air layer between a magnetic head and the magnetic disk. When the rotation of the magnetic disk is to be started or stopped, the magnetic head and the magnetic disk are moved relative to each other in a contact-frictional state. In the CSS system, abrasion on the contact surfaces of both the magnetic head and the magnetic disk is advanced by a frictional force of contact sliding. In addition, if fine dust is present during recording or reproduction, the magnetic head may be brought into contact with the surface of the magnetic disk at high speed to cause a large frictional force between the magnetic head and the surface of the magnetic disk, thereby destroying the magnetic head and or the magnetic thin film. Especially in a metal magnetic thin film medium, since a friction coefficient of the metal magnetic thin film is large and the thickness of the film is small, the above problem conspicuously arises.
To solve the above problem, i.e., to improve a corrosion resistance of the magnetic recording medium and lubricating properties on its surface, Japanese Patent Laid-Open No. 61-208620 discloses a magnetic recording medium in which a carbon protective film is formed on a metal magnetic thin film and a liquid lubricating agent is coated on the protective film. Also, Japanese Patent Laid-Open No. 61-160834 discloses a magnetic recording medium in which an inorganic oxide film consisting of, e.g., SiO
2
formed on a metal magnetic thin film directly or via a first protective film and a liquid lubricating agent such as a fluorine-containing oil, e.g., perfluoroalkylpolyether is coated thereon. In addition, Japanese Patent Laid-Open No. 61-208618 or 61-220120 discloses a method of increasing a bonding force between a lubricating organic film and an inorganic oxide protective film to improve adhesion properties.
However, in the prior art in which the liquid lubricating agent is coated on the carbon protective film, a bonding force between the lubricating agent and the protective film is weak. Therefore, when the CSS is repeatedly performed, the effect of the lubricating agent is gradually reduced to increase a frictional force between the magnetic head and the magnetic disk medium. In addition, since the carbon protective film is abraded, no satisfactory abrasion or damage resistance can be obtained.
In the prior art in which the inorganic oxide film is formed as the uppermost layer of the protective film of the magnetic disk medium and the lubricating agent having a polar group or a functional group is coated on the surface of the inorganic oxide film, the bonding force between the protective film and the lubricating agent is increased. However, it is difficult to coat a lipophilic lubricating agent on the entire surface of the hydrophilic protective film without forming fine pinholes. Therefore, coating of the lubricating agent is sometimes not performed on the entire surface of the protective film to expose the protective film not having a solid lubricating effect on the surface of the magnetic disk medium. In this case, when the CSS operation is repeatedly performed, film destruction is caused on a portion not coated with the lubricating agent.
OBJECTS AND SUMMARY OF THE INVENTION
The present invention has been made to solve the above conventional problems and has as its object to provide a magnetic recording medium having a surface which is not deteriorated even by frequent contact with a magnetic head upon driving or stopping of the magnetic recording medium, and a method of manufacturing the same.
It is another object of the present invention to provide a magnetic recording medium which does not cause a large frictional force between a magnetic head and the surface of the magnetic recording medium and therefore does not allow the magnetic head to destroy a magnetic thin film, and a method of manufacturing the same.
It is still another object of the present invention to provide a method of manufacturing a magnetic recording medium, which can convert silicon in a protective film into a silicon oxide by oxidation at a high speed within a short time period, thereby manufacturing a magnetic recording medium at a low cost.
The present invention is a magnetic recording medium in which a magnetic thin film is formed on a substrate directly or via an undercoating film, a protective film is formed on the magnetic thin film, and a lubricating organic film is formed on the protective film, wherein the protective film contains carbon and silicon, and silicon in at least an interface in contact with the organic film and in the vicinity of the interface is partially or entirely a silicon oxide. That is, the magnetic recording medium of the present invention contains, as components of the protective film in contact with the lubricating organic film, carbon and a silicon oxide, or carbon, silicon and a silicon oxide.
In order to maintain solid lubricating properties of the protective film and improve adhesion properties with respect to the lubricating organic film to be overcoated, the silicon oxide in the protective film may be uniformly present in the thickness direction of the protective film or may have a concentration distribution in the thickness direction. In particular, the silicon oxide is preferably contained in a large amount in an interface with respect to the lubricating organic film and in the vicinity of the interface and contained in only a small amount or not contained at all on the magnetic thin film side because the solid lubricating properties and the adhesion properties can be maintained and magnetization characteristics of the magnetic thin film are not degraded by oxidation upon formation of the protective film on the magnetic thin film.
The content of silicon in the protective film according to the present invention is preferably 1% to 30% (atomic %) with respect to the content of carbon. If this value is less than 1%, an Si—O coupling is hardly generated at the surface, so that an adhering force of oil is not improved and the effect is not entirely attained. In turn, in the event that a sufficient amount of oil is applied on the surface, an amount of wear at a continuous vibrating test (a drag test) at the head or a continuous sliding test (a pin disk test) at the same ball material as that of the head member is preferably less as an amount of silicon is increased. However, in turn, in the even that the value is more than 30%, the Si—C coupling in the film is increased, resulting in that a film breakage form is changed from a mild wearing as that of carbon less than that to a severe wearing (a wearing with the film breakage) and an anti-scaring characteristic is decreased and the head is easily crushed if the head is contacted with the disk during CSS. in addition, in the even that an amount of oil is less or that a partial loss in one disk is found, the film is broken into CSS and so this is not preferable. A value less than 30% indicating a mild wearing is preferable. A more preferable value is 5 to 25% . An effect of improving an adhering force of oil with Si—O coupling at the surface is remarkable at a value more than 5% and a CSS characteristic is improved, so that this value is more preferable. In addition, a value of amount of Si less than 25% is more superior in view of an anti-damage characteristic and this is more preferable even in the event that the oil is
Katayama Shinya
Sato Toshiyuki
McDonald Rodney G.
Nippon Sheet Glass Co. Ltd.
Woodcock & Washburn LLP
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