Stock material or miscellaneous articles – Composite – Of metal
Reexamination Certificate
2002-05-17
2004-09-14
Thibodeau, Paul (Department: 1773)
Stock material or miscellaneous articles
Composite
Of metal
C428S692100, C360S016000, C360S017000
Reexamination Certificate
active
06790534
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to a magnetic transfer master medium provided on the surface thereof with protrusion portions formed in a pattern for transmitting data to a magnetic recording medium, and in particular to a magnetic transfer master medium for transferring data to a perpendicular magnetic recording medium.
Further, the present invention relates to a magnetic transfer method of employing the magnetic transfer master medium according to the present invention to transfer data to a perpendicular magnetic recording medium, and a magnetic transfer master medium forming method.
2. Description of the Related Art
Generally speaking, with regard to magnetic storage mediums, there is a demand for increased storage capacity and low cost. Further desired are so-called high-speed access mediums, which are capable of advantageously reading out the data of a desired location in a short time. Examples of these mediums include the high speed magnetic recording mediums (magnetic disk mediums) utilized in hard disk apparatuses and flexible disk apparatuses. So-called tracking servo technology, wherein the magnetic head accurately scans a narrow width track to achieve a high S/N ratio, plays a substantial role in attaining the high storage capacity thereof. A servo signal, address data signal, replay clock signal, etc., used for tracking within a certain interval occurring in one rotation of the disk are “preformatted”, that is, recorded on the disk in advance.
Magnetic transfer methods realizing accurate and efficient preformatting, wherein the data such as a servo signal or the like borne on a master medium is magnetically transferred therefrom to a magnetic recording medium, have been proposed in, for example, Japanese Unexamined Patent Publication Nos. 63(1988)-183623, 10(1998)-40544, and 10(1998)-269566.
According to these magnetic transfer technologies, a master medium having an uneven pattern corresponding to the data that is to be transferred to a slave medium (a magnetic recording medium) is prepared. By bringing this master medium brought into close contact with a slave medium to form a conjoined body, and applying a transfer magnetic field thereto, a magnetic pattern corresponding to the data (e.g., a servo signal) borne on the master medium is transferred to the slave medium. The preformatting can be performed without changing the relative positions of the master medium and the slave medium; that is, while the two media remain stationary. Therefore not only is it possible to perform an accurate recording of the preformat data, it becomes possible to advantageously do so in an extremely short time.
However, as to the magnetic recording medium, two possibilities are longitudinal magnetic recording mediums provided with an easy magnetization axis in the horizontal direction in relation to the surface of the magnetic layer thereof, and perpendicular magnetic recording mediums provided with an easy magnetization axis in the vertical direction in relation to the surface of the magnetic layer thereof; however, in current practice, longitudinal magnetic recording mediums are generally employed, and the magnetic transfer technology described above has also been developed focusing mainly on the longitudinal magnetic recording mediums as the magnetic recording medium of choice. On the other hand, if a perpendicular magnetic recording medium is employed, an increase in data storage capacity can be expected in comparison to the longitudinal magnetic recording mediums.
For cases in which a magnetic transfer is performed on a perpendicular magnetic recording medium, a magnetic field must be applied in the perpendicular direction with respect to the surface of the magnetic layer thereof; wherein the optimal conditions differ in contrast to cases in which a magnetic transfer is performed on a longitudinal magnetic recording medium.
For example, when a magnetic transfer is performed to a perpendicular magnetic recording medium, the magnetic disorder is large at the border portions between the inverse magnetization portions and the uninverted magnetization portions, wherein a problem arises in that the signal quality is not favorable. Based upon the analysis by the inventors of the present invention, it has become clear that this problem is due to an insufficient constraint of the magnetic flux of the inverse magnetization portions, and is the cause of a reduction in signal quality.
Further, when a perpendicular magnetic transfer is to be performed, the thickness of the pattern of protrusion portions formed by the magnetic layer of the master medium is made thin. Because the magnetic pole distance generated to pass a magnetic field through vertically is short (diamagnetic field), and there is no assistance from adjacent protrusion portions in constraining the magnetic flux between protrusion portions, etc.; it is difficult to realize sufficiently favorable signal quality by providing a soft magnetic layer having a simple form.
SUMMARY OF THE INVENTION
The present invention has been developed in view of the forgoing circumstances, and it is an object of the present invention to provide a magnetic transfer master medium capable of performing a favorable magnetic transfer onto a perpendicular magnetic recording medium.
The magnetic transfer master medium according to the present invention is a magnetic transfer master medium comprising a substrate provided with a surface on which protrusion portions having a magnetic layer have been formed for transferring data to the magnetic layer of a perpendicular magnetic recording medium, wherein
the magnetic layer is also formed in the depression portions between the protrusion portions so that the magnetic layer formed on the protrusion portions and the magnetic layer formed in the depression portions are magnetically linked, and
the ratio of the thickness of said magnetic layer to the track direction width of the magnetic layer of the protrusion portions is greater than or equal to 0.8, and less than or equal to 3.
Here, the expression “a surface on which protrusion portions having a magnetic layer” refers to the portions protruding from base of the depression portions before the magnetic layer has been formed therebetween; wherein, a magnetic layer is formed over at least the tip portion of the these protrusion portions, and the protrusion portions themselves may be formed from the magnetic layer.
Further, the expression “are magnetically linked” refers to the passing through the magnetic layer of the protrusion portions of the greater part of the magnetic flux that passes through the magnetic layer of the depression portions when a transfer magnetic field is applied in the direction of the thickness of the protrusion portions; and does not refer to whether or not the magnetic layer has been formed as a continuous, connected layer over the protrusion portions and in the depression portions.
Further, the referent of “track direction” is the direction corresponding to the direction along the track formed on the slave medium by the magnetic transfer.
Note that it is advantageous, for example, that the transfer data be servo signals.
The magnetic transfer master medium according to the present invention is advantageously utilized in a magnetic transfer method wherein: the magnetic layer of the protrusion portions of said magnetic transfer master medium and the magnetic layer of the perpendicular magnetic recording medium are conjoined to form a conjoined body; and a transfer magnetic field is applied to said conjoined body in the direction perpendicular to the magnetic layer of said perpendicular magnetic recording medium so as to transfer the data from the master medium to the magnetic layer of said perpendicular magnetic recording medium. Here, the referents of “conjoined” include not only to the state wherein the respective surfaces of both of said mediums are in complete close contact with each other, but also states wherein said mediums are disposed in a state wherein a uniform interva
Komatsu Kazunori
Nishikawa Masakazu
Fuji Photo Film Co. , Ltd.
Sughrue & Mion, PLLC
Thibodeau Paul
Uhlir Nikolas J.
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