Dynamic magnetic information storage or retrieval – Record copying – Contact transfer
Reexamination Certificate
2001-07-03
2003-11-11
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
Record copying
Contact transfer
C360S125020
Reexamination Certificate
active
06646820
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to a method of magnetically recording predetermined information signals on a magnetic recording medium used in a magnetic recording/reproducing device.
BACKGROUND ART
Recently, a magnetic recording/reproducing device has been increasing in recording density in order to achieve a small size and large capacity. Especially, in the field of a hard disk drive used as a typical magnetic memory, apparatuses with an areal recording density of more than ten gigabits per square inch (15.5 Mbits/mm
2
) are already available on the market. Practical use of memories with an areal recording density of 20 gigabits per square inch (31.0 Mbits/mm
2
) has been discussed. 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 linear recording density due to the improvements of a medium performance and a head-disk interface performance, and the advent of a new signal processing method such as “partial response”. Recently, however, the rate of increase in track density exceeds that of linear recording density greatly, which is a primary factor for the increase in areal recording density. The 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 the track pitch will reach the sub micron range in the near future along with further improvement of the head performance.
In order that a head scans such narrow tracks correctly to reproduce signals with a high S/N ratio, a technique of tracking servo of the head plays an important role. A hard disk drive to which such a tracking servo technique is applied has areas (hereafter referred to as “preformat”) where a tracking servo signal, an address data signal, and a reproduction clock signal are recorded at predetermined angles over the circumference of a disk, that is, over 360 degrees. The magnetic head reproduces such signals every predetermined interval, so that the magnetic head can scan a track correctly while the head position is verified and corrected.
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 positioning accuracy is required in recording the signals. In a conventional hard disk drive, a disk is incorporated into the drive, and then using a special servo recording apparatus, preformat recording is carried out with a magnetic head whose position is controlled precisely.
In the preformat recording of a servo signal, an address data signal, a reproduction clock signal, and the like using a magnetic head as described above, there have been problems as follows.
First, the recording using a magnetic head is basically linear recording utilizing the relative movement between the magnetic head and a magnetic recording medium, and therefore, in the above-mentioned method of recording using the special servo recording apparatus while the magnetic head position is controlled precisely, preformat recording takes a long time and the servo recording apparatus is quite expensive, thus increasing the cost.
Second, there is a problem in that due to the spacing between a magnetic head and a recording medium and diffusion of the recording magnetic field caused by the shape of a pole provided in the magnetic head, magnetization at the track edges of the recorded preformat signals lacks steepness in transition. In a current tracking servo technique, a head position is detected based on a change amount of reproduction amplitude when the magnetic head deviates from a track to be scanned. Therefore, it is required not only that the head scans a track correctly with a high S/N ratio as in reproducing data signals recorded in an area between servo areas, but also that in a signal track formed by the preformat recording, the magnitude of reproduction amplitude is steeply changed when the magnetic head deviates from a track to be scanned, i.e. the off-track characteristic is steep. The above-mentioned problems go against these requirements and make it difficult to carry out the precise tracking servo technique in the submicron track recording expected in the future.
In order to solve the aforementioned problems in the conventional preformat recording using a magnetic head, the following method has been disclosed.
For instance, JP 10-40544 A discloses the following method. That is, magnetic portions of a ferromagnetic material are formed on a substrate in a pattern corresponding to information signals, which then is used as a master information carrier. The surface of the master information carrier is brought into contact with a surface of a sheet-like or disc-shaped magnetic recording medium on which a ferromagnetic film or a ferromagnetic powder coating layer is formed, and a predetermined magnetic field is applied. Then, the magnetized pattern corresponding to the information signals formed in the master information carrier is recorded into a magnetic recording medium.
In the method disclosed in JP 10-40544 A, with a recording magnetic field generated from the ferromagnetic film on the surface of the master information carrier magnetized in one direction, a magnetized pattern corresponding to the ferromagnetic film pattern in the master information carrier is transfer-recorded into the magnetic recording medium. In other words, a ferromagnetic film pattern corresponding to a tracking servo signal, an address data signal, a reproduction clock signal, or the like is formed on the surface of the master information carrier by photolithography or the like, so that preformat corresponding to the pattern can be recorded on the magnetic recording medium.
The conventional recording with a magnetic head is basically a dynamic track recording based on the relative movement between the head and a medium. On the contrary, the method described above is characterized by a static area recording without being accompanied by relative movement between the master information carrier and a medium. With such a characteristic, the technique disclosed in JP 10-40544 A can provide the following quite useful effects with respect to the aforementioned problems in a preformat recording.
First, since the areal recording is employed, a significantly shorter time is required for the preformat recording as compared to that in a conventional recording method using a magnetic head. In addition, the expensive servo recording apparatus for carrying out recording while the magnetic head position is controlled precisely is not required. Consequently, the productivity in the preformat recording can be increased considerably and the production cost can be reduced.
Second, since the static recording is carried out without being accompanied by relative movement between the master information carrier and a medium, the surface of the master information carrier and the surface of a magnetic recording medium can be brought into close contact with each other, thus minimizing the spacing between the both in recording. Furthermore, since no diffusion of the recording magnetic field due to the shape of a pole provided in the magnetic head is caused, magnetization at the track edges of the recorded preformat signals has excellent steepness in transition compared to the case of recording with a conventional magnetic head, thus achieving more accurate tracking.
In the recording of information signals using such a magnetic transfer technique, an arranged pattern corresponding to information signals provided in a master information carrier is transfer-recorded into a magnetic recording medium as a magnetized pattern at one time. Therefore, it is important that high density information signals are recorded uniformly and stably throughout the whole area of t
Ban Yasuaki
Hamada Taizou
Hashi Hideyuki
Ishida Tatsuaki
Kita Hiromi
Davidson Dan I
Hudspeth David
Matsushita Electric - Industrial Co., Ltd.
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