Disk biasing for manufacture of servo patterned media

Details Disk biasing for manufacture of servo patterned media Disk biasing for manufacture of servo patterned media

2002-01-28

2004-06-29

Klimowicz, William (Department: 2652)

Dynamic magnetic information storage or retrieval

Record copying

C360S099080, C360S098080, C065S305000, C425S406000, C425S810000, C264S001700, C264S207000

Reexamination Certificate

active

06757116

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to methods and apparatus for forming servo patterns in annular disk-shaped substrates for recording media utilized in high areal, high track density applications. The invention has particular utility in the manufacture of magnetic data/information storage and retrieval media, e.g., hard disks utilized in computer and computer-related applications.
BACKGROUND OF THE INVENTION
Magnetic recording media are widely used in various applications, particularly in the computer industry. Referring now to
FIG. 1
, shown therein, in simplified, schematic cross-sectional view, is a portion of a dual-sided, thin-film magnetic disk medium
1
of the type contemplated by the present invention, comprising a rigid, non-magnetic substrate
10
, typically comprised of an aluminum (Al) alloy, e.g., Al—Mg. Alternative materials for use as substrate
10
include glass, ceramics, glass-ceramics composites and laminates, polymers, and other non-magnetic metals and alloys. Al-based substrate
10
is provided, in sequence, at both major surfaces, with a polished and/or textured amorphous Ni—P underlayer
12
, a polycrystalline seed layer
14
, typically a Cr-based layer deposited by sputtering, a magnetic layer
16
comprised of a ferromagnetic material, e.g., an oxide or a Co-based alloy, a protective overcoat layer
18
, typically of a diamond-like carbon (DLC) material, and a lubricant topcoat layer
20
, e.g., of a fluorine-containing polymer.
In operation of medium
1
, the magnetic layer
13
can be locally magnetized by a write transducer or write head, to record and store data/information. The write transducer creates a highly concentrated magnetic field which alternates direction based on the bits of information being stored. When the local magnetic field produced by the write transducer is greater than the coercivity of the recording medium layer
13
, then the grains of the polycrystalline medium at that location are magnetized. The grains retain their magnetization after the magnetic field produced by the write transducer is removed. The direction of the magnetization matches the direction of the applied magnetic field. The pattern of magnetization of the recording medium can subsequently produce an electrical response in a read transducer, allowing the stored medium to be read.
Thin film magnetic recording media are conventionally employed in disk form for use with disk drives for storing large amounts of data in magnetizable form. Typically, one or more disks are rotated on a central axis in combination with data transducer heads. In operation, a typical contact start/stop (“CSS”) method commences when the head begins to slide against the surface of the disk as the disk begins to rotate. Upon reaching a predetermined high rotational speed, the head floats in air at a predetermined distance from the surface of the disk due to dynamic pressure effects caused by the air flow generated between the sliding surface of the head and the disk. During reading and recording operations, the transducer head is maintained at a controlled distance from the recording surface, supported on a bearing of air as the disk rotates, such that the head can be freely moved in both the circumferential and radial directions, allowing data to be recorded on and retrieved from the disk at a desired position. Upon terminating operation of the disk drive, the rotational speed of the disk decreases and the head again begins to slide against the surface of the disk and eventually stops in contact with and pressing against the disk. Thus, the transducer head contacts the recording surface whenever the disk is stationary, accelerated from the static position, and during deceleration just prior to completely stopping. Each time the head and disk assembly is driven, the sliding surface of the head repeats the cyclic sequence consisting of stopping, sliding against the surface of the disk, floating in air, sliding against the surface of the disk, and stopping.
It is considered desirable during reading and recording operations, and for obtainment of high areal recording densities, to maintain the transducer head(s) as close to the associated recording surface(s) as is possible, i.e., to minimize the “flying height” of the head(s). Thus a smooth recording surface is preferred, as well as a smooth opposing surface of the associated transducer head, thereby permitting the head and the disk surface to be positioned in close proximity, with an attendant increase in predictability and consistent behavior of the air bearing supporting the head during motion.
Disk drives typically comprise a magnetic head assembly mounted on the end of a support or actuator arm which positions the head radially over the disk surface. If the actuator arm is held stationary, the magnetic head assembly will pass over a circular path on the disk surface known as a track, and information can be read from or written to that track. Each concentric track has a unique radius, and reading and writing information from or to a specific track requires the magnetic head to be located above the track. By moving the actuator arm, the magnetic head assembly is moved radially over the disk surface between tracks.
The disk drive must be able to differentiate between tracks on the disk and to center the magnetic head over any particular track. Most disk drives use embedded “servo patterns” of magnetically recorded information on the disk. The servo patterns are read by the magnetic head assembly to inform the disk drive of the track location. Tracks typically include both data sectors and servo patterns. Each data sector contains a header followed by a data section. The header may include synchronization information to synchronize various timers in the disk drive to the speed of disk rotation, while the data section is used for recording data. Typical servo patterns are described in, for example, U.S. Pat. Nos. 6,086,961 and 6,139,936, the entire disclosures of which are incorporated herein by reference.
Adverting to
FIG. 2
, shown therein, in simplified, schematic plan view, is a magnetic recording disk
30
having a data zone
34
including a plurality of discrete servo tracks, and a contact start/stop (CSS) zone
32
. A discrete servo pattern
40
is formed on or within the data zone
34
, and includes a number of data track zones
38
separated by servo tracking zones
36
. The data storage function of disk
30
is confined to the data track zones
38
, while servo tracking zones
36
provide information to the disk drive which allows a read/write head to maintain alignment on the individual, tightly-spaced discrete data tracks.
Although only a relatively few of the servo tracking zones are shown in
FIG. 2
for illustrative simplicity, it should be recognized that the discrete track patterns of the media contemplated herein may include several hundreds of servo zones to improve head tracking during each rotation of the disk. In addition, the servo tracking zones need not be straight radial zones as shown in the figure, but may instead comprise arcs, intermittent zones, or irregularly-shaped zones separating individual data tracks.
Referring now to
FIG. 3
, shown therein in simplified, schematic perspective view, is an enlarged portion of a discrete servo track pattern
40
formed on or within the recording media thin film layer structure
41
(corresponding to layers
12
-
20
of FIG.
1
), which in turn is disposed on the surface of substrate
42
for a discrete track medium (corresponding to substrate
10
of FIG.
1
). The various elements or features of pattern
40
are generally defined by a difference in height between recessed zones or regions
44
and raised zones or regions
46
. As illustrated, pattern
40
includes a pair of discrete track zones
38
separated by a servo tracking zone
36
.
Servo tracking zone
36
generally includes track identification (ID) bars
50
and tracking position bars
52
. ID bars
50
provide the identification for each of the discrete tracks
48
of the discrete track p

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