Coating processes – Centrifugal force utilized
Utility Patent
1998-05-22
2001-01-02
Edwards, Laura (Department: 1734)
Coating processes
Centrifugal force utilized
C427S337000, C427S359000, C118S696000, C118S106000, C118S107000, C118S109000, C118S052000, C118S056000, C118S257000, C118S264000
Utility Patent
active
06168831
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to magnetic storage media, and in particular to rigid magnetic disks used in computer disk drives.
Computers and other types of equipment often read and write magnetic flux patterns from magnetic media. One of the preferred types of magnetic media is the rigid, or “hard”, disk. Hard disk drives have been used in computer systems for over thirty years to store digital data, and offer low cost, high recording capacity, and relatively rapid data retrieval. While the basic principle of reading magnetic patterns on rotating disks remains the same, components of the disk drive, particularly the read-write head (“head”) and the disks have significantly evolved.
The first disks were made by coating a rigid platter, as large as 24 inches in diameter, with magnetic particles, such as iron oxide particles, mixed in a resin. More recently, thin-film technology has been used to sputter a thin film of magnetic metal on a platter that is typically about 3.5 inches in diameter. A metallic film offers 100 times the magnetization of the older, particulate films, thereby producing the same amount of magnetic flux from a much thinner film. A thinner film allows more narrow magnetic cells, which represent a data bit, to be formed. The more narrow magnetic cell results in higher recording and storage densities. Additionally, a metallic thin film may be formed on a very smooth platter. Smooth films allow the head to “fly” closer to the magnetic cells, yielding higher readback amplitudes.
Surface roughness limits how low a head can approach the media, and adds to the overall noise contribution of the magnetic layer. Advancements in the design of recording heads, particularly the introduction of magnetroresistive (MR) heads, have required continuing reduction in surface roughness. Current MR media, capable of storing recording densities of 3 Gbit/in
2
have surfaces with roughness values of about 1 nm. Future surfaces for storing 10 Gbit/in
2
are expected to have roughness an order of magnitude lower than the current media.
Such smooth surfaces do not allow the head to land without suffering “stiction” forces. Stiction is a term commonly used in the disk drive industry to describe the sliding friction of a head across a disk as the disk accelerates in rotational velocity to its operating speed. The head will fly above the disk at the operating height once the disk is rotating at full speed. On start-up (when the disk is turned on and begins spinning) or in the event of a drop in rotational speed, the head may dip closer to the disk, resulting in stiction. Stiction forces may arise from a variety of sources, including a localized vacuum created between the head and the disk, and capillary action between liquid present on either the disk or the head.
To avoid excessive stiction on start-up some disks have textured landing zones, where the head can land when the disk is turned off. These landing zones are textured to allow the head to lift off the disk with no more than 1-2 grams of drag. These landing zones may also be lubricated with a liquid lubricant to further improve the contact-start-stop performance of the head. The lubricant is typically applied by dipping or spraying methods, which are quick and inexpensive, but which coat the entire disk with lubricant. Unfortunately, the presence of liquid lubricant in the data zone may create stiction problems in the data zone of the disk, and in the landing zone of the disk if the head picks up liquid lubricant from the data zone and transfers this excess lubricant to the landing zone.
SUMMARY OF THE INVENTION
The present invention provides an apparatus for achieving differential lubrication thicknesses between the landing zone and the data zone of a magnetic disk, and related methods.
In one embodiment, the apparatus rotates a lubricated magnetic disk on a spindle. A roller presses an absorbent tape against a selected portion of the disk and the absorbent tape extracts a portion of the mobile lubricant from the surface of the disk. The disk or roller move(s) laterally in relation to each other so that mobile lubricant is removed from a zone of the lubricated disk, such as the data zone, while mobile lubricant is left in another zone of the disk, such as the landing zone. In another embodiment, a solvent is applied to the absorbent tape and/or the disk to facilitate removal of mobile lubricant from the data zone.
A further understanding of the nature and advantages of the dual zone lubricated disk of the present invention may be realized by reference to the remaining portions of the specification and the attached drawings.
REFERENCES:
patent: 4895098 (1990-01-01), Akagawa et al.
patent: 5674582 (1997-10-01), Eltoukhy et al.
patent: 5863609 (1999-01-01), Yamamoto
Khan M. Yunas
Wei Bo
Edwards Laura
Hyundai Electronics America
Townsend and Townsend / and Crew LLP
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