Dynamic magnetic information storage or retrieval – Record copying – Contact transfer
Reexamination Certificate
2001-02-28
2003-11-18
Faber, Alan T. (Department: 2651)
Dynamic magnetic information storage or retrieval
Record copying
Contact transfer
C360S016000
Reexamination Certificate
active
06650490
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method for magnetic transfer to be used for transfer of a recording information to a magnetic recording medium in a magnetic recording/reproducing apparatus of large capacity and high recording density. In particular, the invention relates to a method for magnetic transfer to be used in the recording of servo signal, address signal, other ordinary video signal, audio signal, data signal, etc. to a magnetic recording medium of large capacity and high recording density.
With rapid development and progress in the utilization of digital image, amount of information to be handled in personal computers and other devices has extensively increased. Because of the increase of the amount of information, there are now strong demands on a magnetic recording medium, which has larger capacity to record the information and can be manufactured at low cost and requires shorter time for writing and reading operations.
In a high density recording medium such as hard disk or in a high density floppy disk type magnetic recording medium represented by ZIP (Iomega Inc.), information recording area has narrower track compared with the floppy disk now commonly used. In order that magnetic head can scan over narrow track width and signals can be recorded or reproduced with high S/N ratio, it is necessary to perform accurate scanning by the tracking servo technique.
In a large capacity magnetic recording medium such as a hard disk or a removable type magnetic recording medium, servo signal for tracking or address information signal, reproduction clock signal, etc. are recorded with a certain spacing between them within one turn of the disk. By reproducing these signals with a given spacing, the magnetic head accurately scans over a track while checking and correcting the position of the head. It is generally practiced that these signals are recorded on the magnetic recording medium in advance in a process called “preformat” at the time when the magnetic recording medium is manufactured.
Accurate positioning is required for the recording of signals such as servo signal for tracking, address information signal, reproduction clock signal, etc. In this respect, after the magnetic recording medium is incorporated in a drive, preformat recording is performed by a magnetic head under strict position control using a special-purpose servo recording system.
However, in the preformat recording of signal such as servo signal, address information signal, or reproduction clock signal by the magnetic head, much time is required for the preformat recording in order to perform the recording with the magnetic head under strict position control using a special-purpose servo recording system. Also, with the increasing requirements on higher magnetic recording density, the amount of signals to be recorded by the preformat recording is increased, and this means that still more time is required. Therefore, in the manufacture of a magnetic recording medium, the percentage of the cost required for the preformat recording process such as servo signals in the total manufacturing cost is increased, and there are strong demands to reduce the cost for this process.
On the other hand, a method has been proposed to perform magnetic transfer of the preformat information from a master carrier to a slave medium without recording the preformat information for each track. For instance, such transfer technique is disclosed in JP-63183623(A), JP-10040544(A), and JP-10269566(A).
According to the method described in JP-10040544(A) or JP-10269566(A), surface irregularities (convex and concave portions) corresponding to the information are formed on the surface of a substrate used as the master carrier for magnetic transfer. The surface of the master carrier for magnetic transfer where ferromagnetic thin film is formed at least on the surface of convex portions is brought into contact with the surface of sheet-like or disk-like magnetic recording medium where ferromagnetic thin film or ferromagnetic power coating layer is formed. Or, by exciting a ferromagnetic material on the surface of convex portions through application of AC bias magnetic field or DC magnetic field, magnetized pattern to match the surface irregularities is recorded on the magnetic recording medium.
According to this method, a predetermined preformat information is formed on the slave medium by closely fitting the surface of convex portions of the master carrier for magnetic transfer to the magnetic recording medium for preformatting, to the slave medium, and by exciting the ferromagnetic material of the convex portion. Thus, the recording can be carried out statically without changing relative positions of the master carrier and the slave medium, and accurate preformat recording can be achieved. Moreover, the time required for the recording can be reduced.
This magnetic transfer method is a method to transfer by bringing both the master carrier and the slave medium in contact with each other in static state. As a result, damage seldom occurs to the master carrier for magnetic transfer or to the slave medium in the process of servo signal recording, and high durability can be ensured.
As the magnetic substance to be used for the master carrier for magnetic transfer, soft magnetic material is generally used. Based on the concept that it would be better in the magnetic substance to have a magnetic layer with lower anisotropy field (Hk) and to be saturated with lower magnetic field in order to have higher transfer efficiency, a material with anisotropy field of lower than Hk<8.0×10
−2
kA/m (1 Oe) has been considered as a possible candidate substance. However, when magnetic transfer is performed on a magnetic layer with anisotropy field of lower than Hk<8.0×10
−2
kA/M (1 Oe), signal output and half-width of magnetic transfer are changed and signal quality varies. Also, when anisotropy field (Hk) of the master carrier is increased, the signal of magnetic transfer is turned to less sharp, and output is decreased.
It is an object of the present invention to provide a method for preventing deterioration of the quality of the signal transferred when a recording information recorded on a master carrier for magnetic transfer is transferred to a slave medium.
SUMMARY OF THE INVENTION
The present invention provides a magnetic transfer method for performing magnetic transfer to a magnetic recording medium, whereby relation between anisotropy field (Hk) of a master carrier for magnetic transfer and coercive force (Hc) of a slave medium satisfies the following condition:
4×10
−4
<(
Hk/Hc
)<2×10
−1
.
Further, the present invention provides the magnetic transfer method as described above, wherein the master carrier for magnetic transfer having a magnetic layer with a magnetic recording information recorded thereon is closely fitted to the slave medium where the information is to be transferred, and a magnetic recording information of the master carrier for magnetic transfer is transferred to the slave medium, whereby magnetization of the slave medium is performed by initial DC magnetization in track direction, and then, the master carrier for magnetic transfer is closely fitted to the slave medium processed by initial DC magnetization, a magnetic field for transfer is applied in a direction opposite to the direction of the initial DC magnetization on the surface of the slave medium, and magnetic transfer is performed.
DESCRIPTION OF THE PREFERRED EMBODIMENT
According to the present invention, when a recording information is transferred to a magnetic recording medium by magnetic transfer, it is possible to prevent deterioration of the quality of the signal transferred by magnetic transfer if magnitude of anisotropy field (Hk) of the master carrier is at a constant level with respect to coercive force (Hc) of the slave medium.
In the magnetic transfer of the recording information, soft magnetic material is generally used as the master carrier for magnetic transfer. In pa
Faber Alan T.
Fuji Photo Film Co. , Ltd.
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