Magnetic field application apparatus, magnetic transfer apparatus and method for producing magnetic recording medium

1. A magnetic field application apparatus for initially magnetizing a slave medium and/or for reversing magnetization thereof in magnetic transfer of a signal pattern onto the slave medium,

wherein the magnetic transfer is performed by initially magnetizing the slave medium in a predetermined direction, by placing the slave medium and an original disk for transfer in close contact with each other after initial magnetization and by applying a magnetic field in a direction opposite to that of initial magnetization so as to

reverse magnetization of the slave medium based on a pattern on a surface of the original disk for transfer, the apparatus comprising:

a pair of magnetic field application means, each of which is arranged, at least during application of a magnetic field, on either side of a magnetic field application target so as to face each other,

and which generate a magnetic field in a desired direction, wherein

each of the magnetic field application means includes a pair of magnetic portions which generate a magnetic field in a desired direction from one of the magnetic portions toward the other magnetic portion, and of which the polarities on the side facing the magnetic field application target are different from each other, wherein each of the magnetic portions is formed so that magnetic force applied to the magnetic field application target becomes weaker stepwise or continuously from the side of the magnetic portion, facing the other magnetic portion, toward the opposite side thereof,

wherein each magnetic portion of the pair of magnetic portions includes a plurality of magnets which are arranged so that magnetic force applied to the magnetic field application target becomes weaker from the side of the magnetic portion, facing the other magnetic portion, toward the opposite side thereof.

2. A magnetic field application apparatus as defined in claim 1 , wherein each magnetic portion of the pair of magnetic portions includes a plurality of magnets which are arranged so that a distance between each of the plurality of magnets and the magnetic field application target becomes longer from the side of the magnetic portion, facing the other magnetic portion, toward the opposite side thereof.

3. A magnetic field application apparatus as defined in claim 1 , wherein the slave medium is disk-shaped, and wherein the pair of magnetic field application means applies a magnetic field in a track direction to the magnetic field application target, the apparatus further comprising:

a reverse magnetic field generation means for generating a magnetic field in a direction opposite to that of the magnetic field generated by the magnetic field application means, wherein the reverse magnetic field generation means is provided on the side of the pair of magnetic field application means, closer to the center of the magnetic field application target.

4. A magnetic field application apparatus as defined in claim 3 , wherein the magnetic field application means and the reverse magnetic field generation means on a first side of the magnetic field application target are symmetrical to the magnetic field application means and the reverse magnetic field generation means on the other side thereof.

5. A magnetic field application apparatus as defined in claim 1 , wherein at least one of the pair of magnetic field application means further includes a permanent magnet between the pair of magnetic portions, wherein the permanent magnet is magnetized in a direction perpendicular to that of magnetization of the pair of magnetic portions, and wherein the permanent magnet generates a magnetic field in the same direction as that of the magnetic field generated from one of the pair of magnetic portions toward the other magnetic portion.

6. A magnetic transfer apparatus for transferring a signal pattern onto a slave medium by initially magnetizing the slave medium in a predetermined direction, by placing the slave medium and an original disk for transfer in close contact with each other after initial magnetization and by applying a magnetic field in a direction opposite to that of initial magnetization so as to reverse magnetization of the slave medium based on a pattern on a surface of the original disk, the apparatus comprising:

a magnetic field application apparatus for initially magnetizing the slave medium and/or for reversing magnetization thereof, as defined in claim 1 .

7. A method for producing a magnetic recording medium, the method comprising the steps of:

initially magnetizing a slave medium in a predetermined direction;

placing the slave medium and an original disk for transfer in close contact with each other after initial magnetization; and

applying a magnetic field in a direction opposite to that of initial magnetization so as to reverse magnetization of the slave medium based on a pattern on a surface of the original disk for transfer, wherein the slave medium is initially magnetized and/or magnetization thereof is reversed using a magnetic field application apparatus as defined in claim 1 .

8. A magnetic field application apparatus as defined in claim 1 , wherein the plurality of magnets are joined together without any gaps therebetween.

9. A magnetic field application apparatus as defined in claim 1 , wherein the plurality of magnets of a first magnetic portion of the plurality of magnetic portions is symmetrical to the plurality of magnets of a second magnetic portion with respect to the central plane between the pair of magnetic portions.

10. A magnetic field application apparatus as defined in claim 1 , wherein each of the plurality of magnets making up each magnetic portion of the plurality of the magnetic portions is of the same polarity.

11. A magnetic field application apparatus as defined in claim 1 , wherein the magnetic field in the opposite direction of the desired direction generated by each magnet of the plurality of magnets is canceled out by a magnetic field in the desired direction generated by an adjacent magnet on an outer side of each of the magnets.

12. A magnetic field application apparatus as defined in claim 1 , wherein the pair of magnetic portions are permanent magnets.

13. A magnetic field application apparatus as defined in claim 1 , wherein the side of the magnetic portion facing the other magnetic portion is closer to the magnetic field application target than the opposite side thereof.