Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the record
Reexamination Certificate
1999-05-13
2003-04-15
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the record
C360S078110, C360S075000
Reexamination Certificate
active
06549360
ABSTRACT:
TECHNICAL FIELD
The present invention relates to magnetic recording media containing substantially radially distributed servo-marks and to a method for manufacturing such magnetic recording media. The present invention has particular applicability in forming micromachined servo-marks for use in high areal recording density magnetic recording media with increased data reading speed.
BACKGROUND ART
Thin film magnetic recording disks and disk drives are conventionally employed for storing large amounts of data in magnetizable form. In operation, a typical contact start/stop (CSS) method involves a floating transducer head gliding at a predetermined distance from the surface of the disk due to dynamic pressure effects caused by air flow generated between the sliding surfaces of the transducer head and the disk. During reading and recording (writing) 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 transducer head can be freely moved in both the circumferential and radially directions allowing data to be recorded on and retrieved from the surface of the disk at a desired position in a data zone.
Conventional magnetic recording media comprise a surface with a dedicated inner annular landing zone on which the transducer head is parked during non-reading and/or non-recording periods, and a data zone on which information is recorded and read. In conventional hard drives, data are stored in terms of bits along tracks. On each track, eight bits form a byte and bytes of data are grouped as sectors. Reading or writing a sector requires knowing the physical location of the data in the data zone so that the servo-controller of the disk drive can accurately position the read/write heads in the correct location at the correct time. As the drive for greater areal recording density increases, it is necessary to increase track recording density.
Conventional disk drives contain several disks, e.g., four, with two read/write heads associated with each disk for a total of eight read/write heads. One conventional approach to the servo-sensing problem is to dedicate the entire upper surface of the first disk, i.e., the top disk, for a servo-surface, and the associated read/write head is employed to read the servo-marks with feedback to the other read/write heads via the servo-controller. Thus, the upper surface of the top disk is not employed for recording data, which is antithetic to the increasing demands for high areal recording density.
Another conventional approach to the servo-sensing problem comprises the use of prerecorded embedded servo-information and dedicated radial spokes. One such type of conventional magnetic recording medium
10
is schematically illustrated in FIG.
1
and comprises data fields
11
having data tracks
12
and radially extending servo-fields
13
. Each such radial servo-field
13
typically has the same width as a data bit, e.g., about 1.0 &mgr;m, but are about 4 to 5 times longer than the data bit, e.g., about 0.4-0.5 &mgr;m vis-à-vis 0.1 &mgr;m. Such radially extending servo-fields
13
are written magnetically and divided into different fields. The first field is typically about 100 &mgr;m to about 120 &mgr;m long and is designed for informing the read/write head where the servo-track begins. The second field is coded by a different pattern to identify the track position. The third and fourth fields are employed for a comparison of track alignment. The fifth field is generally an empty field to inform the read/write head that the servo-track is ending and a data track is beginning. The servo-bits are much larger than the data bits to avoid confusion. After servo-writing, the data tracks are formatted according to the embedded servo-marks and data can then be written between the servo-marks and subsequently erased. Disadvantageously, such conventional approaches to the servo-sensing problem consume a large amount of [areal] area for servo-tracks, thereby reducing the amount of area available for recording the data.
Williams et al., in U.S. Pat. No. 5,120,927, disclose the formation of optical servo-tracks in the form of continuous or non-continuous concentric circles.
There exists a need for a magnetic recording medium having servo-marks which occupy a reduced area of the surface of the magnetic recording medium thereby increasing available area for recording data. There also exists a need for efficient, economical methodology enabling micromachining of a disk surface to provide servo-marks, thereby enabling an increase in areal recording density.
DISCLOSURE OF THE INVENTION
An advantage of the present invention is a magnetic recording medium having a micromachined servo-marks and increased areal recording density.
Another advantage of the present invention is a method of manufacturing a magnetic recording medium having micromachined servo-marks and increased areal recording density.
Additional advantages and other features of the invention will be set forth in the description which follows and in part will be apparent to those having ordinary skill in the art upon examination of the following or may be learned from the practice of the present invention. Advantages of the present invention may be realized and particularly pointed out in the appended claims.
According to the present invention, the foregoing and other advantages are achieved in part by a magnetic recording medium comprising a surface having a data zone containing data tracks with magnetically recorded servo-information; and a distribution of laser textured pits forming a plurality of servo-marks capable of being sensed to enable accurate reading of the servo-information and positioning of a read/write head in the data zone.
A further aspect of the present invention is a method of manufacturing a magnetic recording medium, the method comprising laser texturing a surface of a non-magnetic substrate to form a distribution of pits functioning as servo-marks capable of being sensed to enable reading magnetically recorded servo-information in a data track and accurate positioning of a read/write head on a data zone.
Embodiments of the present invention comprise exposing the surface of a non-magnetic substrate to a laser light beam to form a plurality of protrusions and pits having a substantially circular or substantially elliptical cross section that extend substantially radially across the data zone. The surface of the substrate is then polished, as by chemical-mechanical polishing, to remove the protrusions leaving the radially extending pits having substantially circular or substantially elliptical cross sections. The micromachined pits have relatively small dimensions thereby significantly reducing the size of the servo-marks, i.e., the amount of areal real estate used for sensing the beginning and end of magnetically recorded servo-information and, hence, increasing the available recording area.
Additional advantages and other features of the present invention will become readily apparent to those skilled in this art from the following the detailed description, wherein only the preferred embodiment of the present invention is shown and described, simply by way of illustration of the best mode contemplated for carrying out the present invention. As will be realized, the present invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the present invention. Accordingly, the drawings and description should be regarded as illustrative in nature, not as restrictive.
REFERENCES:
patent: 5120927 (1992-06-01), Williams et al.
patent: 5296995 (1994-03-01), Yonezawa et al.
patent: 5488595 (1996-01-01), Takeuchi et al.
Nguyen Thanh Duc
Shih Chung-Yuang
Xuan Jialuo Jack
Hudspeth David
Seagate Technology LLC
Slavitt Mitchell
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