Dynamic magnetic information storage or retrieval – Record medium – Disk
Reexamination Certificate
1997-06-13
2001-03-20
Miller, Brian E. (Department: 2754)
Dynamic magnetic information storage or retrieval
Record medium
Disk
C360S237000, C360S097010
Reexamination Certificate
active
06205002
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to magnetic disks for use in disk drives with sliders which contact the disk when not operating. More particularly the invention relates to methods for using laser texturing to form a contact start/stop region on the disks.
BACKGROUND OF THE INVENTION
The magnetic surfaces of the disks used for data storage must be extremely smooth with peak-to-valley roughness of some thin film disks being less than 100 Angstroms. The design of most disk drives allows the sliders to rest on the disk surface when the disk is not spinning. If the sliders were allowed to rest on a very smooth surface, the result would be unacceptably high stiction forces between the disk surface and the sliders. For high areal density recording, the slider must fly in close proximity to the disk surface which requires that the surface be very smooth. The trend is, therefore, toward lower flying heights and smoother disks. To reduce the stiction forces between sliders and smooth disks, a band on the disk surface may be deliberately roughened by laser texturing to form a contact start/stop (CSS) region. While the roughened CSS region decreases stiction, it has the undesirable effect of increasing the energy dissipation during disk spin up and spin down. Energy dissipation is directly related to wear.
Various techniques for creating CSS regions have been proposed. Published unexamined Japanese patent application (PUPA) 4-362517 describes the use of a groove in the disk surface adjacent to the CSS in which one rail of the slider rests when the disk is not operating. Alternatively it describes the use of a round protrusion on which the slider rail can rest. Each of these techniques results in the slider being tilted from a parallel position on the disk surface. PUPA 4-38716 suggests cutting spiral grooves into the landing zone under the slider rails. Anonymous Research Disclosure 29563 published in 1988 suggests that “[s]liders with multiple rails may need textured landing zones for one or more of the rails.”
Laser texturing of a CSS is described by Ranjan, et al., in J. Appl. Phys. April 1991 p. 5746ff. The average surface roughness (Ra) was varied by altering the beam current. U.S. Pat. No. 5,528,922 describes the use of increased number of laser pulses to increase the height of a peripheral ridge in crater shaped bumps. U.S. Pat. No. 5,062,021 describes the use of laser created bumps to form a CSS region, controlling depth and height of the bumps by varying the laser power and pulse duration, and altering the shape of the bumps by varying the laser beam inclination relative to the disk surface.
SUMMARY OF THE INVENTION
The present invention is a magnetic disk and a disk drive using the disk. The invention reduces the energy dissipated and, therefore, the wear at the head-disk interface during spin up and spin down when the slider is actually contacting the disk surface. This is accomplished by modifying the topography of the contact start/stop (CSS) region on the disk which the slider contacts. The CSS region is conceptually divided into three circular zones on the planar surface the with middle zone having a topography which is different from the inner and outer zones. In the various embodiments of the invention the middle zone topography is manipulated to reduce the energy dissipation during startup and shutdown without sacrificing stiction reduction. In the preferred embodiment the magnetic disk has a series of bumps formed by laser heating which serve as a CSS region. The plurality of bumps on the planar surface form a circular band with at least inner, middle and outer zones in the circular band. In one embodiment the bumps in the middle zone have an average height above the planar surface which is less than the average height above planar surface of the bumps in the side zones. In another embodiment density of bumps in the middle zone is made lower than the density of bumps in the side zones. In a third embodiment diameter of bumps in the middle zone is smaller than in the side zones. The range of bump diameters of interest is typically 1-30 microns. In a fourth embodiment the middle zone is left untextured so that it has the same topography as the data area with no bumps, i.e., zero bump height. Any combination of height, diameter and density reduction for the middle zone can be used for alternative embodiments. If the center rail or pad of the slider has the lowest flying height, the topography of the middle zone is modified to reduce the energy dissipation. The modification depends on the ABS design (location and dimensions of the rails or pads, force on the lowest flying spot on the slider), flying height vs velocity, the pitch of the slider, and the velocity of the disk, etc. The goal is to minimize the energy dissipation or wear through appropriate matching of the slider and disk designs. The width of the zones is selected according to the dimensions of the particular slider which will be used with the disk. The inner and outer zones are arranged to support the side rails of the slider. The boundary between adjacent zones need not be abrupt, the changes in the bump height, diameter, or density (or any combination thereof) can be gradual. The number of zones can vary depending on the design of the slider and where it flies. When a recessed middle zone (reduced height or no bumps) is used with a three rail or pad slider with a trailing center pad, a particular advantage occurs in inducing a positive pitch to the slider which aids in early take-off and reduced energy dissipation. In the case of reduced density bumps, the contact area is reduced for the center pad.
A disk drive using the disk of the invention includes a latch for positioning the inner and outer rails of the slider over the inner and outer zones of the CSS region during the spin up or spin down of the disk.
REFERENCES:
patent: 4664963 (1987-05-01), Sakai et al.
patent: 4939614 (1990-07-01), Shirakura et al.
patent: 5062021 (1991-10-01), Ranjan et al.
patent: 5208713 (1993-05-01), Lindsay et al.
patent: 5319511 (1994-06-01), Lin
patent: 5528922 (1996-06-01), Baumgart et al.
patent: 5550696 (1996-08-01), Nguyen
patent: 5586040 (1996-12-01), Baumgart et al.
patent: 5595791 (1997-01-01), Baumgart et al.
patent: 5729399 (1998-03-01), Albrecht et al.
patent: 5734522 (1998-03-01), Shrinkle
patent: 5768058 (1998-06-01), Hofland
patent: 3-162716 (1991-07-01), None
patent: 4-11324 (1992-01-01), None
patent: 4-38716 (1992-02-01), None
patent: 4-362517 (1992-12-01), None
patent: 5-151733 (1993-06-01), None
patent: 5-189758 (1993-07-01), None
IBM TDB Magnetic Disk With Structured Start/Stop (S/S) Track Vo. 27 No. 10A Mar. 1985.
Laser Texturing For Low-Flying-Height Media by R. Ranjan et al J. Appl Phys. 69 (8) Apr. 15, 1991.
Head Parking Zone Research Disclosure Nov. 1988.
Baumgart Peter Michael
Gregory Thomas Allen
Nayak Ulla Vasant
Nguyen Thao Anh
Ramirez Michael Luis
Altera Law Group LLC
International Business Machines - Corporation
Miller Brian E.
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