Master information carrier and method for manufacturing magnetic disc using the same
View Patent ↗A master information carrier capable of manufacturing a magnetic recording medium in which a preformat recording of information signals causing no reproduction signal detection errors arising from a pulse shift of a reproduction waveform is performed. A master information carrier 1 has an array of ferromagnetic thin films 3 arranged according to the pattern of information signals and is used for forming magnetization 4 of a pattern corresponding to the array pattern of the ferromagnetic thin film 3 in a magnetic recording medium by applying a magnetic field while opposing the master information carrier 1 against a magnetic recording medium 2 . Each of the ferromagnetic thin films 3 is formed such that each pattern length A becomes equal to a length including a correction amount α in addition to a length a between magnetic transition areas 6 of the magnetization 4 to be formed in the magnetic recording medium 2.
1. A method for producing an in-plane magnetic recording medium, the method comprising the step of:
bringing a surface of a master information carrier in close contact with a surface of the in-plane magnetic recording medium, the surface of the master information carrier having an information signal according to a figuration pattern of an array of ferromagnetic thin films that are deposited on a surface of a substrate, and applying a magnetic field thereto, so as to record the information signal corresponding to the array of the ferromagnetic thin films as magnetization information in the in-plane magnetic recording medium,
wherein a length of each ferromagnetic thin film on the master information carrier, corresponding to a distance between a pair of magnetic transition areas adjacent to each other in the magnetization information recorded in the in-plane magnetic recording medium, is set to be larger than a distance between the magnetic transition areas that is desirable for a signal recorded in the in-plane magnetic recording medium.
2. The method according to claim 1 , further comprising the step of:
magnetizing the in-plane magnetic recording medium uniformly in an opposite polarity to a polarity of the magnetic field by applying a d.c. magnetic field to the in-plane magnetic recording medium, prior to the step of bringing the surface of the master information in close contact with the surface of the in-plane magnetic recoding medium and applying the magnetic field thereto.
3. The method for producing an in-plane magnetic recording medium according to claim 1 ,
wherein the length of each ferromagnetic thin film on the master information carrier is a+α,
where
a represents the desirable distance between the magnetic transition areas on the in-plane magnetic recording medium, and
α represents a correction amount that is determined so that a quantity of a pulse shift of an actual reproduction waveform from a desirable reproduction waveform does not exceed a permissible limit of a detection window width for a reproduction pulse obtained from the in-plane magnetic recording medium, the actual reproduction waveform being a reproduction waveform of an information signal recorded in the in-plane magnetic recording medium according to the master information carrier.
4. The method for producing an in-plane magnetic recording medium according to claim 3 ,
wherein
the ferromagnetic thin film on the master information carrier is a cobalt film with saturation magnetic flux density of 1.6 T,
the ferromagnetic thin film has a film thickness between 0.2 μm and 1.0 μm,
the desirable distance a between the magnetic transition areas is between 0.5 μm and 5.0 μm,
the in-plane magnetic recording medium has coercivity in a range between 150 kA/m and 300 kA/m, and
the correction amount a is in a range between 0.05 μm and 1.0 μm.
5. The method for producing an in-plane magnetic recording medium according to claim 3 ,
wherein
the ferromagnetic thin film on the master information carrier is a cobalt film with saturation magnetic flux density of 1.6 T,
the ferromagnetic thin film has a film thickness between 0.2 μm and 1.0 μm,
the desirable distance a between the magnetic transition areas is between 0.5 μm and 5.0 μm,
the in-plane magnetic recording medium has coercivity in a range between 150 kA/m and
300 kA/m, and
α/a is in a range between 0.01 and 0.8.
6. A method for producing an in-plane magnetic recording medium, the method comprising the step of:
bringing a surface of a master information carrier in the close contract with a surface of the in-plane magnetic recording medium, the surface of the master information carrier having an information signal according to a figuration pattern of an array of ferromagnetic thin films that are deposited on a surface of a substrate, and applying a magnetic field thereto, so as to record the information signal corresponding to the array of the ferromagnetic thin films as magnetization information in the in-plane magnetic recording medium,
wherein a distance between a pair of ferromagnetic thin films on the master information carrier, corresponding to a distance between a pair of magnetic transition areas adjacent to each other in the magnetization information recorded in the in-plane magnetic recording medium, is set to be smaller than a distance between the magnetic transition areas that is desirable for a signal recorded in the in-plane magnetic recording medium.
7. The method according to claim 6 , further comprising the step of:
magnetizing the in-plane magnetic recording medium uniformly in an opposite polarity to a polarity of the magnetic field by applying a d.c. magnetic field to the in-plane magnetic recording medium, prior to the step of bringing the surface of the master information in close contact with the surface of the in-plane magnetic recoding medium and applying the magnetic field thereto.
8. The method for producing an in-plane magnetic recording medium according to claim 6 ,
wherein
the distance between a pair of ferromagnetic thin films on the master information carrier is b−α,
where
b represents the desirable distance between the magnetic transition areas on the in-plane magnetic recording medium, and
α represents a correction amount that is determined so that a quantity of a pulse shift of an actual reproduction waveform from a desirable reproduction waveform does not exceed a permissible limit of a detection window width for a reproduction pulse obtained from the in-plane magnetic recording medium, the actual reproduction waveform being a reproduction waveform of an information signal recorded in the in-plane magnetic recording medium according to the master information carrier.
9. The method for producing an in-plane magnetic recording medium according to claim 8 ,
wherein
the ferromagnetic thin film on the master information carrier is a cobalt film with saturation magnetic flux density of 1.6 T,
the ferromagnetic thin film has a film thickness between 0.2 μm and 1.0 μm,
the desirable distance b between the magnetic transition area is between 0.5 μm and 5.0 μm,
the in-plane magnetic recording medium has coercivity in a range between 150 kA/m and 300 kA/m, and
the correction amount α is in a range between 0.05 μm and 1.0 μm.
10. The method for producing an in-plane magnetic recording medium according to claim 8 ,
wherein
the ferromagnetic thin film on the master information carrier is a cobalt film with saturation magnetic flux density of 1.6 T,
the ferromagnetic thin film has a film thickness between 0.2 μm and 1.0 μm,
the desirable distance b between the magnetic transition areas is between 0.5 μm and 5.0 μm,
the in-plane magnetic recording medium has coercivity in a range between 150 kA/m and 300 kA/m, and α/b is in a range between 0.01 and 0.8.