JP2002008229A - Method for magnetic transfer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for magnetic transfer capable of obtaining transferred signals of high quality in a method for magnetic transfer by bringing a master carrier for magnetic transfer into contact with a slave medium. SOLUTION: In the method for magnetic transfer on a magnetic recording medium, a master carrier for magnetic transfer having a magnetic layer with high coercive force and a soft magnetic layer successively formed on a nonmagnetic substrate is used. The master carrier for magnetic transfer and a magnetic recording medium as a slave to receive signal transfer are used in such a manner that the slave medium is preliminarily subjected to initial DC magnetization in the track direction, then the master carrier for magnetic transfer is brought into tightly contact with the slave medium which has been subjected to initial DC magnetization and magnetic transfer is carried out by applying magnetic field for transfer in the opposite direction to the direction of the initial DC magnetization of the slave face.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for magnetically transferring information recorded on a magnetic recording medium for a large-capacity, high-recording-density magnetic recording / reproducing apparatus. The present invention relates to a magnetic transfer method used for recording servo signals, address signals, and other ordinary video signals, audio signals, data signals, and the like.

[0002]

2. Description of the Related Art The amount of information handled by personal computers and the like has been dramatically increased due to the progress of use of digital images and the like. Due to the increase in the amount of information, there is a demand for a large-capacity, inexpensive magnetic recording medium for recording information and a short recording and reading time. High-density recording media such as hard disks, ZIP
In a large-capacity removable magnetic recording medium such as (Iomega), the information recording area is formed of narrow tracks as compared with a floppy (registered trademark) disk, and the magnetic head scans a narrow track width accurately. In order to perform signal recording and reproduction at a high S / N ratio, it is necessary to perform accurate scanning using a tracking servo technique.

Therefore, in a large-capacity magnetic recording medium such as a hard disk or a removable magnetic recording medium, a tracking servo signal, an address information signal, a reproduction clock signal, and the like are provided at a constant angular interval with respect to one rotation of the disk. A recorded area is provided, and the magnetic head reproduces these signals at regular intervals to accurately scan the track while confirming and correcting the position of the head. A method of recording these signals on a magnetic recording medium in advance is called a preformat when the magnetic recording medium is manufactured. Accurate positioning accuracy is required for recording of servo signals for tracking, address information signals, reproduced clock signals, etc.After the magnetic recording medium is incorporated in the drive, the position is strictly controlled using a dedicated servo recording device. Preformat recording is performed by the magnetic head.

However, in the preformat recording of the servo signal, the address information signal, and the reproduction clock signal by the magnetic head, since the recording is performed while strictly controlling the position of the magnetic head using a dedicated servo recording device, it is necessary to perform one recording. Each of these is manufactured by recording one track at a time, and it takes a long time to perform preformat recording. Further, as the magnetic recording density increases, the amount of signals to be preformat-recorded increases, which requires a longer time. Therefore, in the manufacture of a magnetic recording medium, the ratio of the cost required for the preformat recording process of servo signals and the like to the manufacturing cost increases, and it is desired to reduce the cost in this process.

On the other hand, there has also been proposed a system in which preformat information is recorded by magnetic transfer from a master carrier to a slave medium without recording the preformat information one track at a time. For example, JP-A-63-183623, JP-A-10-40544 and JP-A-10-2695
No. 66 introduces a transfer technique. JP-A-63-
In the method described in Japanese Patent Application Laid-Open No. 183623/1998 or Japanese Patent Application Laid-Open No. 10-45544, an irregular shape corresponding to an information signal is formed on the surface of a substrate as a magnetic transfer master carrier, and a ferromagnetic thin film is formed on at least the convex surface of the irregular shape. The surface of the formed magnetic transfer master carrier is brought into contact with the surface of a sheet-shaped or disk-shaped magnetic recording medium on which a coating layer of a composition containing a ferromagnetic thin film or a ferromagnetic powder is formed, or further, an AC bias magnetic field, Alternatively, by applying a DC magnetic field to excite the ferromagnetic material constituting the surface of the convex portion, a magnetization pattern corresponding to the irregular shape is recorded on the magnetic recording medium.

In this method, the surface of a convex portion of a magnetic transfer master carrier is brought into close contact with a magnetic recording medium to be preformatted, that is, a slave medium, and at the same time, a ferromagnetic material constituting the convex portion is excited to form a slave medium. This is a transfer method for forming a record of predetermined preformat information, which allows static recording to be performed without changing the relative position between the magnetic transfer master carrier and the slave medium. The feature is that it is possible and the time required for recording is extremely short.

Further, since this magnetic transfer method is a method in which both the magnetic transfer master carrier and the slave medium are brought into contact with each other in a stationary state to perform the transfer, both the magnetic transfer master carrier and the slave medium in the servo signal recording step are used. This is a method in which damage is less likely to occur and high durability is expected. However, during magnetic transfer to a large number of slave media, there is a case where the signal quality after the magnetic transfer is out of a practical range, and there is a problem in practical use.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magnetic transfer method for preventing deterioration of signal quality due to magnetic transfer when transferring recorded information recorded on a magnetic transfer master carrier to a slave medium. It is an issue.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for performing magnetic transfer on a magnetic recording medium, which comprises using a magnetic transfer master carrier in which a high coercive force magnetic layer and a soft magnetic layer are sequentially formed on a non-magnetic substrate. It can be solved by doing. In addition, as a magnetic transfer method, a magnetic transfer master which has a magnetic layer formed on a portion corresponding to an information signal on the surface of the substrate and a magnetic recording medium which is a slave medium for receiving the transfer are used, and the magnetization of the slave medium is tracked in advance. After the initial DC magnetization in the direction, the master carrier for magnetic transfer and the slave medium with the initial DC magnetization are brought into close contact with each other, and a transfer magnetic field is applied in a direction opposite to the initial DC magnetization direction of the slave surface to perform magnetic transfer. This is a magnetic transfer method using the method. Further, the magnetic recording medium is a magnetic recording medium in which a servo signal is recorded by the above method.

[0010]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for performing magnetic transfer on a magnetic recording medium, comprising: a high coercivity magnetic layer on a non-magnetic substrate; It has been found that the use of a magnetic transfer master carrier having a plurality of magnetic layers in which soft magnetic layers are sequentially formed when H is 0 and M is also 0 when H is 0 can prevent signal quality deterioration due to magnetic transfer. is there.

In the method of performing magnetic transfer by bringing the master carrier for magnetic transfer into close contact with the slave medium, the master carrier for magnetic transfer and the slave medium are brought into close contact with each other, inserted into a magnetic pole portion of a magnetic field applying device, and applied with a transfer magnetic field. Meanwhile, magnetic transfer is performed by rotating at least one of a transfer magnetic field and a contact body between the master carrier for magnetic transfer and the slave medium.

After the magnetic transfer is completed, the transfer magnetic field is reduced to zero, the magnetic pole portion of the magnetic field applying device, the magnetic transfer master carrier and the slave medium are separated, and then the slave medium is separated and taken out from the close contact body. At this time, even when the transfer magnetic field is set to zero, the magnetic pole portion has residual magnetization,
A small magnetic field is applied to the contact body.
Therefore, when removing the adhered body between the magnetic transfer master carrier and the slave medium from the magnetic pole portion, the magnetization direction of the magnetic transfer master carrier changes due to the residual magnetic field of the magnetic field applying device, and the recorded magnetization state is disturbed. It is considered that the signal quality deteriorates.

Therefore, the magnetic field is observed by a Gauss meter, and the applied magnetic field is adjusted to be zero. Then, the adhered body between the master carrier for magnetic transfer and the slave medium is taken out of the transfer device. It was confirmed that a remarkable decrease was generated. It is considered that the magnetization direction of the soft magnetic layer provided on the magnetic layer of the magnetic transfer master carrier changes, and the magnetization state of the slave medium is disturbed, so that the signal quality of the slave medium is significantly reduced. .

It is difficult to completely eliminate the residual magnetization from the transfer magnetic field applying device in the magnetic transfer device. Accordingly, the present invention provides a method for separating a closely adhered body between a magnetic transfer master carrier and a slave medium from a magnetic field applying apparatus, even if a weak magnetic field is present in the transfer device, if the magnetization direction of the magnetic transfer master carrier does not change. It is found that the magnetization state of the slave medium does not disturb, and a magnetic layer having a high coercive force is provided in contact with the soft magnetic layer to prevent a change in the magnetization direction of the soft magnetic layer of the magnetic transfer master carrier. This prevents the signal quality of the magnetic transfer surface of the magnetic transfer master carrier from deteriorating.

The master carrier for magnetic transfer used in the magnetic transfer method of the present invention comprises a nonmagnetic support, a high coercivity magnetic layer made of a high coercivity magnetic material, and a soft magnetic layer formed on the high coercivity magnetic layer. It is. The high coercive force magnetic layer formed on the magnetic transfer master carrier of the present invention has a coercive force Hc of 4
0 kA / m (5000 e) or more and 318 kA m (40
000e) or less. More preferably, 79.6 kA / m (10000 e) or more and 239 kA / m
m (30000e) or less. The preferred thickness of the magnetic layer is 50 nm or more and 800 nm or less, more preferably 1 nm or more.
It is not less than 00 nm and not more than 500 nm.

The high coercive force magnetic layer can be formed by depositing a high coercive force magnetic material on a non-magnetic substrate by a vacuum film forming method such as a sputtering method.
Specifically, as the high coercive force magnetic layer, Co, a Co alloy (CoPtCr, CoCr, CoPtCrTa, CoP
tCrNbTa, CoCrB, CoNi, etc.), Fe, F
A magnetic layer made of e-alloy (FeCo, FePt, FeCoNi) or the like can be given. It is preferable to provide a non-magnetic underlayer on the substrate side of the high coercivity magnetic layer in order to form a desired magnetic anisotropy, and it is necessary to match the crystal structure and lattice constant to the high coercivity magnetic layer. It is.

The high coercivity magnetic layer may be formed on the entire surface of the master carrier for magnetic transfer and patterned with only the soft magnetic layer, or may be formed by patterning both the high coercivity magnetic layer and the soft magnetic layer. Any of the above may be used.

As the non-magnetic underlayer, Cr, CrT
i, CoCr, CrTa, CrMo, NiAl, Ru or the like can be used. The thickness of the nonmagnetic underlayer is preferably 200 nm or more and 1000 nm or less,
More preferably, it is 300 nm or more and 700 nm or less.

The thickness of the soft magnetic layer is preferably 50 nm or more and 800 nm or less, more preferably 100 nm or more and 500 nm or less. In particular,
As the soft magnetic layer, Co, a Co alloy (CoNi, Co
NiZr, CoNbTaZr, etc.), Fe, Fe alloy (F
eCo, FeCoNi, FeNiMo, FeAlSi,
FeAl, FeTaN), Ni, Ni alloy (NiFe)
Can be used. Of these, FeCo and FeCoNi are particularly preferred.

Preferably, a hard carbon protective film such as diamond-like carbon (DLC) is provided on the magnetic layer, and a lubricant layer may be provided on the hard carbon protective film. The protective film preferably has a diamond-like carbon film having a thickness of 5 to 30 nm and a lubricant. The lubricant has an effect of preventing a scratch caused by friction when correcting a shift generated in a contact process when the master carrier for magnetic transfer and the slave medium are brought into close contact with each other.

The master carrier for magnetic transfer used in the magnetic transfer method of the present invention can be prepared by the following method. As the substrate of the magnetic transfer master carrier, a non-magnetic member having a smooth surface such as silicon, aluminum, glass, or synthetic resin can be used.

First, a photoresist is applied on these substrates, and a resist pattern matching the pattern formed by magnetic transfer is formed by pattern exposure or direct scribing. In the case of pattern exposure, a pattern is formed on a substrate by reactive etching, physical etching using argon plasma or the like, or chemical etching using an etchant.

Next, after forming the underlayer to a predetermined thickness by sputtering, a high coercivity magnetic layer is formed to a predetermined thickness using a high coercivity magnetic material as a target.
Further, a soft magnetic material is formed. Thereafter, the photoresist is removed by lift-off. Alternatively, only the convex magnetic layer that comes into contact with the slave medium during magnetic transfer may be manufactured by photofabrication.

As a method for performing fine processing, an injection molding method may be used. Explaining the injection molding method, while rotating a glass substrate coated with a photoresist, a laser modulated in accordance with a servo signal is irradiated to expose the photoresist to the entire glass surface. The resist is developed, and the glass substrate is developed to form irregularities on the glass. Next, plating is performed on the glass substrate on which the unevenness is formed by removing the resist, thereby producing a plating master having the unevenness. Nickel or a nickel alloy can be used as the plating plate material. Further, in order to improve the durability of the plating master, a carbon film such as diamond-like carbon may be formed by sputtering or the like.

Using a plating master, a resin substrate on which a pattern is formed is manufactured by a method such as injection molding. As the resin material, an acrylic resin such as polycarbonate and polymethyl methacrylate, a vinyl chloride resin such as a polyvinyl chloride / vinyl chloride copolymer, an epoxy resin, an amorphous polyolefin, and a polyester can be used. Polycarbonate is preferred in terms of moisture resistance, dimensional stability, cost, and the like. If there is a burr on the formed plating master, it is removed by burnishing or polishing. The groove depth of the pattern is preferably in the range of 50 to 1000 nm. More preferably, it is in the range of 200 to 500 nm.

Hereinafter, the slave medium used in the present invention will be described. As the slave medium, a coating type magnetic recording medium in which ferromagnetic metal particles are dispersed in a binder, or a metal thin film type magnetic recording medium in which a ferromagnetic metal thin film is formed on a substrate can be used. As a coating type magnetic recording medium, Zip1 which is a recording medium for Zip (Iomega) is used.
And a magnetic recording medium such as a high-density floppy disk called "00, Zip250, or HiFD".

As the metal thin film type magnetic recording medium, Co, Co alloy (CoPtCr, CoCr,
CoPtCrTa, CoPtCrNbTa, CoCr
B, CoNi, etc.), Fe, Fe alloys (FeCo, FeP)
t, FeCoNi) can be used. High magnetic flux density, same direction as the magnetic layer of the magnetic transfer master carrier,
That is, it is preferable to have magnetic anisotropy in the in-plane direction for in-plane recording, and to have perpendicular magnetic anisotropy in the case of perpendicular recording because clear transfer can be performed. It is preferable to provide a non-magnetic underlayer below the magnetic layer, that is, on the substrate side, in order to form a necessary magnetic anisotropy, and it is preferable that the crystal structure and lattice constant match the magnetic layer.

[0028]

The present invention will be described below with reference to examples and comparative examples. Example 1 A 3.5-type magnetic transfer master carrier was prepared using a silicon wafer disk as a substrate, a non-magnetic underlayer of Cr having a thickness of 600 nm, and a 25-nm thick CoCrPt (68:20:12 atomic ratio). High coercivity magnetic layer, FeCo (7
(0:30 atomic ratio) and a soft magnetic layer having a thickness of 200 nm was sequentially formed.

The nonmagnetic underlayer and the magnetic layer were formed by a DC sputtering method using a sputtering apparatus (730H, manufactured by Anelva). The nonmagnetic underlayer Cr and the CoCrPt layer as the high coercivity magnetic layer were formed at 200 ° C., and the FeCo layer as the soft magnetic layer was formed at 25 ° C. The pressure of argon during sputtering is Cr: 1.1 × 10 ⁻² Pa.
(8 mTorr), CoCrPt: 2.1 × 10 ⁻³ Pa
(1.5 mTorr), FeCo: 5.0 × 10 ⁻⁴ Pa
(0.36 mTorr). All input power is 2.
80 W / cm ² . Hc of the obtained high coercive force layer is 1
It is 99 kA / m (2500 Oe).

The disk-shaped pattern is radially 2 from the center of the disk.
Radial lines of equal width 5 μm from the position of 0 mm to 40 mm, and the line interval is 8 at the innermost position in the radial direction of 20 μm.
The interval was μm. Patterning was performed only on the soft magnetic layer. The pattern was formed by forming a high coercivity layer magnetic layer as a continuous layer, applying a resist, forming a resist pattern by pattern exposure and development, and then forming a soft pattern on the high coercivity magnetic layer on which the resist pattern was formed. After forming the magnetic layer, the resist was dissolved and removed to form a patterned soft magnetic layer.

As a slave medium, a commercially available coating magnetic recording medium for Zip250 (manufactured by Fuji Photo Film Co., Ltd.) was used. The coercive force Hc of the slave medium is 199k
A / m (25000e). 3 peak magnetic field strength
The initial DC magnetization of the slave medium is performed using an electromagnet device so as to be 98 kA / m (5000 Oe: twice the slave Hc), and then the slave with the initial DC magnetization is brought into close contact with the master carrier for magnetic transfer. 19 using the device
Magnetic transfer was performed by applying a magnetic field of 9 kA / m (2500 Oe). The obtained slave medium was evaluated by the following evaluation method, and the magnetic transfer information was evaluated. The results are shown in Table 1.

EXAMPLE 2 The slave medium described in Example 1 was replaced with a commercially available Iomega Z
Magnetic transfer was performed in the same manner as in Example 1 except that a coating type magnetic recording medium for ip100 (manufactured by Fuji Photo Film) was used and the transfer magnetic field was set to 127 kA / m (1600 Oe), which was the same as the coercive force of the slave medium. Table 1 shows the results.

Example 3 High coercive force of the magnetic transfer master carrier described in Example 1 The production temperature of the magnetic layer was increased to 300 ° C. to promote the segregation of Cr in the magnetic layer, and the coercive force Hc of the magnetic transfer master carrier was increased. 279
Example 1 except that kA / m (3500 Oe) was changed.
The magnetic transfer was performed in the same manner as described above, and the results are shown in Table 1.

Example 4 After applying a resist on a silicon wafer disk, a resist pattern was formed by pattern exposure and development, and then a non-magnetic underlayer, a high coercive force magnetic layer, and a soft magnetic layer were formed. A master carrier for magnetic transfer was manufactured in the same manner as in Example 1 except that the patterned magnetic layer was formed by dissolving and removing the pattern, and magnetic transfer was performed in the same manner as in Example 1, and the results are shown in Table 1. .

Comparative Example 1 Magnetic transfer was carried out in the same manner as in Example 1 except that the high coercive force magnetic layer was not provided on the master carrier described in Example 1, and the results are shown in Table 1. Comparative Example 2 Magnetic transfer was performed in the same manner as in Example 2 except that the high coercive force magnetic layer was not provided on the master carrier described in Example 2, and the results are shown in Table 1. Comparative Example 3 Magnetic transfer was performed in the same manner as in Example 3 except that a high coercive force magnetic layer was not provided on the master carrier described in Example 3, and the results are shown in Table 1.

(Evaluation Method) Measurement of Electromagnetic Conversion Characteristics The signal quality of the transfer signal of the slave medium was evaluated using an electromagnetic conversion characteristic measuring device (SS-60, manufactured by Kyodo Electronics).
The reproduction signal (TAA) of the above device was measured, and 0.85 mV
It was determined to be good if the reproduction output was obtained. Furthermore, the value of 80% of the reproduction signal (TAA) was used as a threshold value, and the number of times the reproduction output was below the threshold value was measured in one round of the disk on the same track. The same measurement was performed for the entire circumference of the disk. If the total number of times (NDO) where the reproduction output was lower than the threshold value was 15 or more, it was determined to be defective.

[0037]

Table 1 High coercivity layer presence / absence TAA (mV) NDO (piece) Example 1 Yes 0.912 Good 9 Good Example 2 Yes 0.862 Good 13 Good Example 3 Yes 0.906 Good 5 Good Example 4 Yes 0.898 Good 6 Good Comparative Example 1 None 0.906 Good 16 Bad Comparative Example 2 None 0.885 Good 21 Bad Comparative Example 3 None 0.896 Good 18 Bad

[0038]

As described above, according to the magnetic transfer method using the magnetic transfer master carrier of the present invention, the productivity can be reduced in a short time to a disk-shaped medium such as a hard disk, a large-capacity removable disk medium, and a large-capacity flexible medium. well,
Preformat recording such as a tracking servo signal, an address information signal, and a reproduction clock signal can be performed with stable magnetic transfer without lowering the quality of a transfer signal.

Claims (3)

[Claims] 1. A method for performing magnetic transfer on a magnetic recording medium, comprising using a magnetic transfer master carrier having a high coercive force magnetic layer and a soft magnetic layer formed sequentially on a nonmagnetic substrate. 2. A magnetic transfer method, comprising: using a magnetic transfer master carrier having a magnetic layer formed on a portion corresponding to an information signal on the surface of a substrate; and a magnetic recording medium serving as a slave to receive transfer. After the initial DC magnetization in the track direction, a magnetic transfer is performed by applying a transfer magnetic field in a direction opposite to the initial DC magnetization direction of the slave surface by bringing the master medium for magnetic transfer into close contact with the slave medium with the initial DC magnetization. 2. The magnetic transfer method according to claim 1, wherein 3. A magnetic recording medium, wherein a servo signal is recorded by the method according to claim 1.