Dynamic magnetic information storage or retrieval – Record copying – Contact transfer
Reexamination Certificate
2000-09-13
2003-08-26
Faber, Alan T. (Department: 2651)
Dynamic magnetic information storage or retrieval
Record copying
Contact transfer
Reexamination Certificate
active
06611388
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a master-information magnetic recording apparatus for recording predetermined master information signals, using a master information carrier, on a magnetic recording medium used in a magnetic recording/reproducing apparatus with large capacity and high recording density.
BACKGROUND ART
A magnetic recording/reproducing apparatus has been increasing in recording density in order to achieve its small size and large capacity. Especially, in the field of a hard disk drive as a typical magnetic recording/reproducing apparatus, apparatuses with an areal recording density of more than five gigabits per square inch (7.75 Mbits/mm
2
) are already available on the market. The practical use of apparatuses with an areal recording density of ten gigabits per square inch (15.5 Mbits/mm
2
) is expected in a few years. Thus, the technique in this field has been progressing rapidly.
One of the technical features that has enabled such high recording density is the increasing track recording density due to the improvements of magnetic recording media, performance of a head-disk interface, and the like and the advent of a new signal processing method such as “partial response”. However, recently the rate of increase in track density exceeds that of track recording density greatly, which is a primary factor for the increase in areal recording density. Practical use of a magneto-resistive type head, which is superior to a conventional inductive type magnetic head in reproduction-amplitude performance by far, has contributed to the increase in track density, and has enabled the reproduction of signals from a track whose width is a few microns or less with a high S/N ratio. It is expected that a track pitch will reach the sub micron range in the near future along with further improvement of the head performance.
A conventional hard disk drive has areas (hereafter referred to as “preformat recording areas”) where master information signals such as a tracking servo signal, an address data signal, and a reproduction clock signal are recorded, so that a magnetic head can scan such a narrow track correctly and reproduce the signals with a high S/N ratio. The preformat recording areas are spaced at predetermined angles over the circumference of a disk, that is, over 360 degrees. The magnetic head reproduces such signals every redetermined period to verify its position and corrects its displacement in a radial direction of magnetic disk as required, thus scanning a track correctly.
The master information signals such as a tracking servo signal, an address data signal, and a reproduction clock signal are to be reference signals for the magnetic head to scan a track correctly. Therefore, precise track-positioning accuracy is required in recording the signals. In a conventional hard disk drive, a magnetic disk and a magnetic head are incorporated into a drive in advance. Then the master information signals are recorded with the unique magnetic head incorporated in the drive, using a special servo track recording apparatus. In this case, the preformat recording is performed while an external actuator equipped with the servo track recording apparatus precisely controls the position of the unique magnetic head incorporated in the drive, thus securing the required track-positioning accuracy.
However, the above mentioned preformat recording with the unique magnetic head incorporated in the drive using the special servo track recording apparatus in the prior art has some problems as follows.
The first problem is that the preformat recording requires a long time in the above-mentioned method, since the recording using a magnetic head is basically linear recording by utilizing relative movement between the magnetic head and a magnetic recording medium. In addition, the servo track recording apparatus is quite expensive, thus increasing the cost required for the preformat recording.
The first problem would become more serious along with the increase in track density in the magnetic recording/reproducing apparatus. In addition to the increase in the number of tracks in the radial direction, the following reasons cause the increase in the time required for the preformat recording. That is, the more the track density increases, the greater the precision that is required for positioning the magnetic head. Therefore, preformat recording areas where the information signals such as the tracking servo signal and the like are recorded have to be located at a smaller angular interval over one rotation of the disk. Consequently, the preformat information signals to be recorded in the disk increase as the recording density increases. Thus, more time is required for the preformat recording.
Although the magnetic disk media have tended to be decreased in diameter, disks with a large diameter of 3.5 or 5 inches are still in demand. In a disk, the larger the recording area is, the more the preformat information signals to be recorded increase. The time required for the preformat recording greatly influences the cost performance of such large disks.
The second problem is that due to the space between the magnetic head and the magnetic recording medium and diffusion of the recording magnetic field caused by the shape of a pole provided at the tip of the magnetic head, magnetization at the track edges of the recorded preformat signals lacks steepness in transition.
The recording using a magnetic head is basically dynamic linear recording by utilizing relative movement between the magnetic head and a magnetic recording medium. Therefore, a certain space between the magnetic head and the magnetic recording medium cannot be avoided in view of the interface performance between them. Further, as shown in
FIG. 2
, a conventional magnetic head usually has two components performing recording and reproduction respectively. Consequently, the width of a pole
22
at a trailing edge of a recording gap corresponds to a recording track width, and the width of a pole
23
at a leading edge is several times larger than the recording track width.
Both the two conditions mentioned above may cause the diffusive recording magnetic field at recording track edges. As a result, such problems occur that the magnetization at the track edges of the recorded preformat signals lacks steepness in transition or erased areas appear on both sides of a track edge. In a current tracking servo technique, magnetic-head position is detected based on a change amount of reproduction amplitude when the magnetic head deviates from a track to scan. Therefore, it is required not only that the magnetic head scan a track correctly with a high S/N ratio as in reproducing data signals, but also that the amount of reproduction amplitude is steeply changed when the magnetic head deviates from a track to scan, i.e. the off-track characteristic is steep. Consequently, when a magnetization at an edge of a track of the preformat signals lacks steepness in transition, it is difficult to realize the precise tracking servo technique that is required for a submicron track recording in the future.
In order to solve the aforementioned two problems in the preformat recording using a magnetic head, Japanese Laid-open Patent Publication (Tokkai Hei) No. 10-40544 proposes a new preformat recording technique. In this technique, a master information carrier is prepared, which comprises a substrate on which a ferromagnetic film pattern corresponding to preformat information signals is formed. The surface of the master information carrier is brought into contact with a surface of a magnetic recording medium. Then, the ferromagnetic film pattern formed on the master information carrier is magnetized, thus recording a magnetized pattern corresponding to the ferromagnetic film pattern into the magnetic recording medium. According to this preformat recording technique, an excellent preformat recording can be performed efficiently with no sacrifice in other important performance such as S/N ratio of the recording medium and interface performance.
FIG. 2
show
Hamada Taizou
Ishida Tatsuaki
Miyata Keizo
Ryonai Hiroshi
Tohma Kiyokazu
Faber Alan T.
Matsushita Electric - Industrial Co., Ltd.
Merchant & Gould P.C.
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