Dynamic magnetic information storage or retrieval – Record copying – Contact transfer
Reexamination Certificate
2001-10-13
2004-11-02
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
Record copying
Contact transfer
C360S016000
Reexamination Certificate
active
06813105
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an apparatus for magnetically transferring servo data for positioning the magnetic head for data recording and for data reading to a magnetic disc (magnetic recording medium) in a hard disc drive (hereinafter referred to as a “HDD”), that is typically utilized in a peripheral storage apparatus for most computers. Specifically, the present invention relates to a magnetic transfer apparatus, that uses the magnetic transfer techniques for transferring servo data to the so-called perpendicular magnetic recording media, in that the direction of the magnetization recorded therein is perpendicular to the magnetic recording media.
BACKGROUND OF THE INVENTION
The magnetic recording media used for HDD's exhibit a recording density of 20 Gbit per a square inch at the present stage of development and the recording capacity thereof is increasing at the rate of 60% a year. Since the area for recording one bit has become narrower due to the increase of the recording capacity, data recording and data reproduction by the so-called longitudinal magnetic recording method, in that the direction of the magnetization recorded is parallel to the surface (longitudinal direction) of the magnetic recording medium, has become more difficult. To obviate this problem, a so-called perpendicular recording medium, in that the direction of the magnetization recorded is perpendicular to the magnetic recording medium, has been proposed. The perpendicular magnetic recording medium includes a magnetic recording layer of a hard magnetic material and a lining layer of a soft magnetic material for localizing the magnetic fluxes generated by the magnetic head used for recording data in the recording layer.
In the usual HDD's, data is recorded and reproduced by a magnetic head mounted on a floating mechanism called slider, that keeps the magnetic head floating several tens of nanometers above a circular magnetic recording medium rotating. The bit data on the magnetic recording medium is stored in data tracks arranged concentrically on the magnetic recording medium. To record and reproduce data, the magnetic head for data recording and for data reproduction is moved quickly toward an aimed data track and positioned above the aimed data track. Servo data including tracking signals for detecting a relative position of the magnetic head and the data track, address signals and reproducing clock signals are stored on the recording plane of the magnetic recording medium. The servo data corresponding to one data track is stored on the same circle of the data track at a predetermined period of angles. As shown in
FIG. 17
, the servo data is stored in servo data regions, shaped with stripes (or fans) and formed at a predetermined period of angles, and along the data tracks. The servo data is recorded by an exclusive apparatus called servo track writer to a magnetic recording medium mounted on a HDD, so that the centers of the regions storing the signals indicative of the servo data may not deviate from the center of the magnetic recording medium nor from the center of the trajectory of the magnetic head for data recording and for data reproduction.
As described earlier, the recording density of the servo data is inevitably rising with increasing recording density of the magnetic recording medium. Due to the high recording density of the magnetic recording medium, the time necessary to write the servo data with a high density is prolonged, the manufacturing efficiencies of the HDD's are lowered and the manufacturing costs are increased.
Recently, an alternative method has been proposed to obviate the problems of the conventional method, which writes the servo data from a magnetic head of the data track writer for writing the signals indicative of the servo data in the data tracks track by track. The alternative method shortens the time necessary to record the servo data on magnetic recording media by transferring the servo data stored on a master disc to the magnetic recording media recording medium by recording medium by the magnetic transfer techniques.
Japanese Unexamined Laid Open Patent Application H10-40544 discloses a method of transferring servo data to a longitudinal magnetic recording medium from a master disc including convex portions and ferromagnetic concave portions. This publication, however, describes nothing on the magnetic transfer method for perpendicular magnetic recording media. Japanese Unexamined Laid Open Patent Application H11-25455 discloses a scheme that uses a master disc including a groove formed thereon for air feeding and for air sucking to ensure tight contact of the master disc with a magnetic recording medium. This publication, however, describes nothing on the magnetic transfer method for perpendicular magnetic recording media.
FIG.
1
(
a
) is a schematic drawing describing initialization of a longitudinal magnetic recording medium. FIG.
1
(
b
) is a schematic drawing describing magnetic transfer to the longitudinal magnetic recording medium. Referring now to FIG.
1
(
a
), the initialization of the longitudinal magnetic recording medium is an operation that magnetizes the magnetic layer of a magnetic recording medium
1
in a certain direction parallel to the magnetic recording medium by a leakage magnetic field
4
leaking from a gap
3
of a ring head
2
. Referring now to FIG.
1
(
b
), the magnetic transfer is an operation, that applies a magnetic field
7
, opposite to the leakage magnetic field
4
used in the initialization operation, from a gap
6
of a ring head
5
to the magnetic recording medium
1
in tight contact with a master disc for magnetic transfer
8
(hereinafter referred to simply as a “master disc”). Since the leakage magnetic field
7
converges to soft magnetic layers
9
with a high magnetic permeability, the strength of the leakage magnetic field
7
applied to the magnetic recording medium
1
decreases in the portions facing to the soft magnetic layers
9
of the master disc
8
. The strength of the leakage magnetic field
7
applied to the magnetic recording medium
1
does not decrease in the portions not facing to the soft magnetic layers
9
. Therefore, only the portions of the magnetic recording medium
1
not facing to any soft magnetic layer
9
are magnetized by the leakage magnetic field
7
. Thus, servo signals are transferred. As described above, the initialization operation or the transfer operation is conducted by positioning a ring head above one surface of a magnetic recording medium.
FIG.
2
(
a
) is a schematic drawing describing initialization of a perpendicular magnetic recording medium, the magnetization direction thereof is perpendicular thereto. FIG.
2
(
b
) is a schematic drawing describing magnetic transfer onto the perpendicular magnetic recording medium. Referring now to FIG.
2
(
a
), a perpendicular magnetic recording medium
11
is initialized by a perpendicular magnetic field
14
applied thereto from two permanent magnets of single pole type
12
and
12
(hereinafter referred to as “single-pole magnetic heads”) such that the magnetization directs to a direction perpendicular to the perpendicular magnetic recording medium
11
. Referring now to FIG.
2
(
b
), a perpendicular magnetic field
15
, the direction thereof is opposite to that of the perpendicular magnetic field
14
used for initialization, is applied to the perpendicular magnetic recording medium
11
in tight contact with a master disc
8
. The perpendicular magnetic field
15
converges to soft magnetic layers
9
, the magnetic permeability thereof is high. The strength of the perpendicular magnetic field
15
increases in the portions of the perpendicular magnetic recording medium
11
facing to the soft magnetic layers
9
embedded in the master disc
8
. The strength of the perpendicular magnetic field
15
decreases in the portions of the perpendicular magnetic recording medium
11
not facing to any soft magnetic layer
9
. Therefore, the perpendicular magnetic field
15
is effective only
Fuji Electric & Co., Ltd.
Hudspeth David
Negron Daniell L.
Rossi & Associates
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