JPH0916901A - Magnetizing method and magnetic disk - Google Patents

Abstract

PURPOSE: To greatly contribute to a decrease in the error rate of an embossment type magnetic disk. CONSTITUTION: The embossment type magnetic disk which has a servo-pit, etc., in uneven pattern is magnetized. At this time, when the range of the current value determined by the amplitude allowable range in a magnetizing current dependency characteristic graph of a reproduced waveform is Iamp0-Iamp1 and the range of the current value determined by the time allowable range is Iint0-Iint1, the current value which is smaller between the Iamp0 and Iint0 is regarded as the lower limit of a magnetizing current and the current value which is larger between the Iamp1-Iint1 is regarded as the upper limit of the magnetizing current, so that magnetization is performed. Consequently, the magnetic disk can be magnetized so that an optimum reproduced waveform can be obtained by a reproduction system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an embossed magnetic disk and a method of magnetizing the same.

[0002]

2. Description of the Related Art As a storage medium for a computer or the like, a disc-shaped magnetic disk which can be randomly accessed is widely used. Above all, a glass plate, a plastic plate, Alternatively, a magnetic disk (so-called hard disk) using a hard material such as an Al alloy plate having a surface subjected to Ni-P plating or alumite treatment has been used.

A flying magnetic head is usually used for recording / reproducing on / from the magnetic disk. The floating magnetic head is levitated with a minute distance from the rotating disk surface, and the floating magnetic head is moved in the radial direction to scan over a predetermined data track. , Record and reproduce magnetic signals.

In such a magnetic disk recording / reproducing system, in recent years, miniaturization of devices and high density recording have been advanced. Among them, the high density recording of the magnetic disk is performed by increasing the signal linear density or narrowing the track width to increase the number of data tracks per disk.

However, if the track width of the disk is too narrow, for example, during signal reproduction, interference (crosstalk) from magnetic signals recorded on adjacent data tracks is likely to occur and the S / N ratio deteriorates.

Therefore, as a magnetic disk capable of suppressing such crosstalk, there has been proposed an embossed magnetic disk in which a data track, a servo pit portion, and a clock mark are formed as a concavo-convex pattern on a substrate surface.

In this embossed magnetic disk, the uneven shape of the substrate surface is reflected on the surface of the magnetic layer, and the magnetic layer has the same uneven pattern as that formed on the substrate surface. The concave portion and the convex portion are magnetized in opposite magnetization directions.

Therefore, when the convex portions are used as the data tracks, the data tracks are magnetically separated from each other because the concave portions are interposed therebetween. Therefore, it is hard to be influenced by the magnetic signals recorded on the adjacent data tracks, and even when the track width is set to be relatively narrow, a reproduction signal having a high S / N ratio can be obtained.

Here, in such an embossed magnetic disk, the magnetization for magnetizing the concave portion and the convex portion in opposite directions is performed as follows.

That is, a magnetic field is applied from the recording magnetic layer side by a permanent magnet capable of generating a relatively large magnetic field, and the permanent magnet is scanned in the track direction. by this,
The entire surface of the disk is magnetized in one direction regardless of the concave and convex portions (first magnetizing step).

Next, a magnetic field in the direction opposite to that of the permanent magnet is applied from the recording magnetic layer side by a magnetic head which generates a relatively small magnetic field, and the magnetic head is scanned in the track direction. At this time, since the magnetic field generated by this magnetic head is small, the magnetization reversal does not occur due to the spacing loss in the concave portion located away from the magnetic head,
The original magnetization direction is maintained. On the other hand, in the convex portion located near the magnetic head, the applied magnetic field causes magnetization reversal, and the magnetized state is opposite to the previous magnetization direction (second magnetization step).

By the above-mentioned magnetization process, a magnetic disk in which the magnetization directions of the concave and convex portions are opposite to each other can be obtained.

[0013]

By the way, in the embossed type magnetic disk, the shape of the convex portion formed as a servo pit or the like on the substrate is ideally a rectangular shape with a rising angle of 90 °. However, in the case of a substrate manufactured by injection molding, it is usual that the convex portion is formed in a trapezoidal shape with a rising angle of about 45 °.

In such a trapezoidal convex portion, the reproduced waveform obtained when the magnetic head scans the convex portion varies depending on the strength of the magnetic field applied in the second magnetization step during magnetization. Can be seen.

FIG. 7 shows a typical example of a convex portion formed on a magnetic disk and a reproduced waveform thereof. In FIG. 7B, the horizontal axis represents time and the vertical axis represents current value.

As shown in FIG. 7A, a trapezoidal convex portion is formed in this magnetic disk, and the convex portion and the concave portion are magnetized to a size of m ₁ and m ₂ , respectively. When a magnetic head scans the convex portion of such a magnetic disk in the D direction in the figure, as shown in FIG. 7B, the boundary position where the magnetization direction is considered to be reversed on the magnetic disk, In this case, the amplitudes opposite to each other are observed on the gradients on both sides of the convex portion.

In this case, when the strength of the magnetic field applied to the magnetic disk in the second magnetizing step, that is, the current value applied to the magnetic head (hereinafter referred to as the magnetizing current) is changed, the magnetic field is changed. The boundary position where the magnetization direction is reversed changes on the disk. When the magnetizing current is smaller, the boundary position where the magnetization direction is reversed is inside, and conversely, when the magnetizing current is larger, the boundary position where the magnetization direction is reversed is outside. When the boundary position where the magnetization direction is reversed on the magnetic disk changes in this manner, the time interval T of the amplitude changes on the reproduced waveform in accordance with the change of the boundary position.
Also, the amplitude A changes. Therefore, in order to obtain a proper reproduction waveform in the reproduction system, it is necessary to set the magnetizing current in the second magnetization step in consideration of such a change in the reproducing waveform depending on the magnetizing current. Normally, a current value that maximizes the amplitude A of the reproduced waveform is used as the magnetizing current.

However, in various reproducing systems for generating servo signals and the like from the concavo-convex pattern of the magnetic disk, it is preferable that the amplitude of the reproduced waveform is certainly large.
There is also an optimum value for the amplitude time interval in each system. That is, it is not always the optimum condition for the reproduction system that the amplitude of the reproduction waveform is maximum, and the amplitude of the reproduction waveform and the time interval between the amplitudes are considered to meet the standards of the reproduction system. Need to be present. Therefore, in reality, it is difficult to obtain a good reproduction signal from a magnetic disk magnetized with a magnetizing current set only from the amplitude of the reproduced waveform.

Therefore, the present invention has been proposed in view of such a conventional situation, and it is possible to magnetize a magnetic disk so that an optimum reproduction waveform is generated on the reproduction system. An object is to provide a magnetizing method. It is another object of the present invention to provide a magnetic disk capable of generating an optimum reproduced waveform on the reproducing system by using such a magnetizing method.

[0020]

In order to achieve the above object, a magnetizing method of the present invention is applied to a magnetic disk having a recording magnetic layer formed on a non-magnetic substrate having an uneven pattern. When magnetizing the concave portion and the convex portion of the recording magnetic layer in opposite magnetization directions, the current value range determined by the amplitude allowable range on the magnetization current dependence characteristic diagram of the reproduction waveform in the concavo-convex pattern is set to Iamp0- Iamp1, the range of the current value determined by the time allowable range is Iint0
If Iint1, Iamp0 or Iint0
Whichever is smaller is used as the lower limit of the magnetizing current, and I
It is characterized in that the magnetization is performed with the larger current value of amp1 or Iint1 as the upper limit of the magnetization current.

A magnetic disk in which a recording magnetic layer is formed on a non-magnetic substrate on which an uneven pattern is formed, wherein the concave portion and the convex portion of the recording magnetic layer are mutually formed by the magnetizing method according to claim 1. It is characterized by being magnetized in opposite magnetization directions.

[0022]

With respect to the embossed type magnetic disk in which the servo pits and the like are formed as the concavo-convex pattern, the current value range determined by the amplitude allowable range on the magnetization current dependence characteristic diagram of the reproduction waveform is Iamp0 to Iamp1, and the time is allowed. When the range of current values determined by the range is Iint0 to Iint1, the smaller current value of Iamp0 or Iint0 is the lower limit of the magnetization current, and the larger current value of Iamp1 or Iint1 is the magnetization current. When the magnetization is performed as the upper limit of, the magnetic disk is magnetized so that the amplitude of the reproduction waveform and the time interval of the amplitude fall within the allowable range. In the magnetic disk magnetized in this way, a good servo signal can be obtained, so the error rate can be suppressed small.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described with reference to the drawings.

In this embodiment, with respect to a magnetic disk in which a recording magnetic layer is formed on a non-magnetic substrate on which data tracks, servo pits, and clock marks are formed as a concavo-convex pattern, concaves and convexes of the recording magnetic layer are formed. And are magnetized in opposite magnetization directions.

In the magnetic disk to be magnetized, the non-magnetic substrate is produced by injection-molding a polymer material using a stamper die in which a concavo-convex pattern to be formed on the substrate is formed. It is something. Examples of the polymer material include polycarbonate, polyethylene terephthalate, polybutylene terephthalate and the like.

The recording magnetic layer is made of Co, Co-Pt,
Co-Ni, Co-Ni-Cr, Co-Cr, Co-C
It is a metal thin film made of a Co-based alloy such as r-Ta. These thin films are formed by vacuum thin film forming technology such as sputtering.
The surface of the non-magnetic substrate on the side where the concavo-convex pattern is formed is formed so as to have a surface shape that reflects the concavo-convex pattern.

In this embodiment, such a magnetic disk is magnetized so that the concave portion and the convex portion of the recording magnetic layer have opposite magnetization directions. A magnetizing device for performing this magnetization is shown in FIG.

This magnetizing device applies a relatively large magnetic field and a relatively small magnetic field to a magnetic disk 5 fixed by a disk fixing device 10 on a spindle 6, and Magnetic disk 5
It has a magnetic head 1 for generating a reproduction waveform from

The magnetic pole of the permanent magnet 4 is a magnetic disk 5.
The magnetic disk 5 is supported at a minute distance from the disk surface so as to be directed to the side, and is moved in the radial direction of the disk. Therefore, by operating the permanent magnet 4 in the radial direction of the disk while rotating the magnetic disk 5, a magnetic field is applied to the entire surface of the disk by the permanent magnet 4. Although a permanent magnet is used as a magnet for applying a large magnetic field to the magnetic disk 5 here, an electromagnet or a magnetic head may be used instead.

On the other hand, the magnetic head 1 is supported with a minute distance from the disk surface of the magnetic disk 5 so that the magnetic gap faces the magnetic disk 5 side, and is operated to move in the radial direction of the disk. Has been done.

Here, the magnetic head 1 is selected from a magnetization mode in which a magnetic field is applied to the magnetic disk 5 in an arbitrary size and a reproduction mode in which a reproduction waveform is generated from the magnetic disk. The amplifier 7, the A / D conversion device 8, and the controller unit 9 that function in these modes are connected.

The amplifier 7 is for arbitrarily changing the current value (magnetizing current) supplied to the magnetic head 1 in the magnetizing mode, and by changing the magnetizing current, the magnetic head 1 is changed. The magnitude of the magnetic field generated changes.

On the other hand, the A / D converter 8 is for detecting a reproduced waveform in the reproduction mode, and for example, a digital oscilloscope or the like is used. The magnitude of the amplitude of the detected reproduced waveform and the time interval of the amplitude are digitized by the controller unit 9 connected to the A / D converter 8.

Therefore, when the magnetic head 1 is moved in the radial direction of the disk, a magnetic field of arbitrary magnitude is applied to the entire surface of the disk by the magnetic head 1 in the magnetizing mode, and the magnetic field is magnetized in the reproducing mode. The reproduced waveform is detected from the disc on which the reproduction is performed.

In order to perform the magnetization by such a magnetizing device, the magnetic disk 5 to be magnetized is fixed on the spindle 6 so that the side on which the recording magnetic layer is formed is the upper side, and FIG.
A magnetic field is applied by the permanent magnet 4 as shown in FIG.
By the applied magnetic field, the recording magnetic layer of the magnetic disk 5 is magnetized to have a size of m _{2 in} one direction regardless of the concave and convex portions (first magnetizing step).

Next, the magnetic head 1 is set to the magnetizing mode,
As shown in FIG. 3A, an arbitrary magnetizing current is supplied to the magnetic head 1 to generate a magnetic field in the direction opposite to that of the permanent magnet 4. Since the magnetic field generated by this magnetic head 1 is small, magnetization reversal does not occur due to spacing loss in the recesses located away from the magnetic head 1, and the original magnetization direction is maintained. On the other hand, in the convex portion located near the magnetic head, the magnetic field is applied to cause the magnetization reversal, and the state becomes magnetized in the size of m _{1 in the} direction opposite to the previous magnetization direction (second magnetization step). .

Next, from the magnetic disk in which the convex portions and the concave portions are magnetized in the sizes of m ₁ and m ₂ respectively,
In order to observe the reproduced waveform of servo pits, clock marks, etc., the magnetic head scans the convex portions corresponding to these pits. When the magnetic head scans the convex part, A / D
In the converter, as shown in FIG. 3B, reproduced waveforms having amplitudes opposite to each other are observed corresponding to possible boundary positions where the magnetization is reversed on the magnetic disk. In FIG. 3B, the horizontal axis represents time and the vertical axis represents current value. Then, the amplitude A of this reproduced waveform
And the time interval T between the amplitudes is digitized by the control unit (reproduction waveform generating step).

The magnetization of the magnetic disk and the observation of the reproduced waveform are basically performed in the above steps.

Here, in order to magnetize the magnetic disk so that an appropriate reproduction waveform can be obtained in a specific reproduction system, it is important to set the magnetizing current in the second magnetizing step.

In this embodiment, this magnetizing current is set based on the magnetizing current dependence characteristics of the amplitude of the reproduced waveform and the time interval of the amplitude. The magnetizing current dependency characteristic of the magnitude of the amplitude and the time interval of the amplitude is obtained by repeatedly performing the second magnetizing step and the reproducing waveform generating step while changing the magnetizing current.

FIGS. 4 and 5 show characteristic diagrams in which the magnitude of the amplitude of the reproduced waveform and the time interval of the amplitude thus measured are plotted with the magnetizing current as the horizontal axis. It should be noted that FIGS. 4 and 5 show examples in which different magnetic disks are used as samples.

Here, in any of the characteristic diagrams, the magnitude of the amplitude of the reproduced waveform increases depending on the magnetizing current up to a certain value, and thereafter, the magnetizing current increases. Shows a change that decreases depending on. The magnetizing current that maximizes this amplitude is Iamp.

On the other hand, the time interval T of the amplitude increases in a cubic function depending on the magnetizing current. Here, each reproduction system has an optimum value of the time interval of the amplitude. The magnetizing current for which the time interval of the amplitude has this optimum value is Iint. In addition, here, the optimum time interval is about 300 ns.
Assume that

Here, in the case of FIG. 4, the magnetizing current Iamp having the maximum amplitude and the magnetizing current Iint having the optimum time interval T of the amplitude coincide with each other. In such a case, the second magnetization step may be performed using this Iamp (that is, Iint) as the magnetizing current.

On the other hand, in FIG. 5, Iamp has a value smaller than Iint, and these values do not match. In such a case, it is necessary to set the magnetizing current in consideration of the amplitude allowable range of the reproduced waveform and the time allowable range of the amplitude in the reproducing system. The permissible range is a range determined by the servo signal quality after the servo signal is generated, that is, an amplitude range and a time interval range in which the signal quality can be secured at a certain value or more, and varies depending on the reproducing system. A method of setting the magnetizing current in consideration of this allowable range will be described with reference to FIG.

That is, FIG. 6 schematically shows a magnetizing current dependence characteristic of a general reproduction waveform. In FIG. 6, Iam
p0 is a magnetizing current at which the amplitude of the reproduced waveform is equivalent to the lower limit of the amplitude allowable range of the reproducing system, and Iam
p1 is a magnetizing current at which the amplitude of the reproduced waveform corresponds to the upper limit of the allowable amplitude range of the reproducing system.

Iint0 is a magnetizing current whose amplitude time interval has a magnitude corresponding to the lower limit of the time allowable range of the reproduction system, and Iint1 is the amplitude time interval
It is a magnetizing current having a magnitude corresponding to the upper limit of the time permissible range of the reproducing system.

Here, in this characteristic diagram, Iint0 <I
The magnitude relationship is such that amp0 <Iint1 <Iamp1. In such a case, Iint0 to Iamp
1 range, more preferably Iint0 to Iint1 and I
Range where amp0 to Iamp1 overlap, that is, Iamp
The magnetizing current is selected in the range of 0 to Iint1. By magnetizing with such a magnetizing current, the magnetic disk
The amplitude of the reproduction waveform and the interval between the amplitudes are magnetized so as to be values within or close to the permissible range of the reproduction system.

The amplitude permissible range and the time permissible range shown in FIG. 6 are examples, and Iint0, Iint1, and Iam.
The p0 and Iamp1 do not always have the magnitude relationship as described above. Depending on the magnetic disk and playback system,
And Iint0 and Iamp0, Iint1 and Iamp
The magnitude relationship of 1 may be reversed. In any case, Iint0 or Iamp0, whichever is smaller, is used as the lower limit of the magnetizing current, and Iint1 or Iam is set as the lower limit.
If the larger current value of p1 is set as the upper limit of the magnetizing current, similarly, in the magnetic disk, both the magnitude of the amplitude of the reproduction waveform and the interval between the amplitudes are within or within the permissible range of the reproduction system. Will be magnetized to have a value close to.

The above is the setting range of the magnetizing current applicable to general reproducing systems. The reproducing system includes a system giving priority to the magnitude of the amplitude of the reproduced waveform, a system giving priority to the time interval of the amplitude, and the reproduced waveform. There is a system in which the magnitude of the amplitude and the time interval of the amplitude are emphasized by certain weights. If such a weighting is obvious, then
It is more preferable to set the magnetizing current according to the weighting.

For example, the optimum value Iopt of the magnetizing current of the system which gives priority to the magnitude of the amplitude of the reproduced waveform is Iint.
If 0 <Iamp <Iint1, then Iopt = I
amp, Iamp <Iint0 and Iamp1> Iin
If t0, then Iopt = Iint0, Iamp>
If Iint1 and Iamp0 <Iint1, then Iopt = Iint1.

Further, the optimum value Iopt of the magnetizing current of the system giving priority to the time interval of amplitude is Iamp0 <Iint <Ia.
In the case of mp1, Iopt = Iint, Iint <
If Iamp0 and Iint1> Iamp0, then Iopt = Iamp0Iint> Iamp1 and Iin
If t0 <Iamp1, then Iopt = Iamp1
It is.

Further, the optimum value Iopt of the magnetizing current of the system in which the magnitude of the amplitude of the reproduced waveform and the time interval of the amplitude are emphasized with certain weights is Iopt = (mIamp + nIint) / (m + n) (however, m, n is an integer). Here, m is weighting of the magnitude of the amplitude of the reproduced waveform, and n is weighting of the time interval of the amplitude, which is set according to the reproducing system.

As described above, the magnetizing current is weighted for each of the amplitude of the reproduced waveform and the time interval of the amplitude in the reproducing system, and Iamp0, Iamp, Iamp1, Iint0, I on the characteristic diagram of the reproduced waveform magnetizing current.
If the magnitude relation between int and Iint1 is determined, it can be determined to a certain value. Therefore, for example, a control circuit of the above magnetizing device may be equipped with a judgment circuit for deriving an optimum magnetizing current according to the above-mentioned conditions, and the amplifier may be controlled according to the derived current value information. For example, it is possible to automatically magnetize the magnetic disk with an optimum magnetizing current.

[0055]

As is apparent from the above description, in the magnetizing method of the present invention, the reproducing waveform depends on the magnetizing current with respect to the embossed magnetic disk in which the servo pits and the like are formed as the concavo-convex pattern. The current value range determined by the amplitude allowable range on the characteristic diagram is Iamp0 to Iamp1, and the current value range determined by the time allowable range is Iint0 to Ii.
When nt1, Iamp0 or Iint0, whichever is smaller, is used as the lower limit of the magnetizing current, and Iam
Since the magnetization is performed with the larger current value of p1 and Iint1 as the upper limit of the magnetization current, the magnetic disk can be magnetized so that an optimum reproduction waveform can be obtained in the reproduction system. Therefore, it can largely contribute to the reduction of the error rate of the embossed magnetic disk.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a magnetizing device for carrying out a magnetizing method of the present invention.

FIG. 2 is a schematic diagram for explaining a first magnetization step in the magnetizing device.

3A and 3B are diagrams for explaining a second magnetizing step in the magnetizing device, FIG. 3A is a schematic diagram showing a magnetized state of a magnetic disk, and FIG. 3B is a diagram showing a magnetized magnetic disk. It is a characteristic view which shows the reproduced waveform obtained.

FIG. 4 is a characteristic diagram showing an example of a magnetization current dependence characteristic of a reproduced waveform.

FIG. 5 is a characteristic diagram showing another example of a magnetizing current dependence characteristic of a reproduced waveform.

FIG. 6 is a current value range Ia determined by an allowable amplitude range.
It is a schematic diagram for demonstrating the range Iint0-Iint1 of the electric current value determined by mp0-Iamp1 and a time permissible range.

FIG. 7 is for explaining a reproduced waveform, (a)
Is a schematic diagram showing a magnetized state of the magnetic disk, (b)
FIG. 3 is a characteristic diagram showing a reproduction waveform obtained from a magnetized magnetic disk.

Claims (2)

[Claims] 1. A magnetic disk comprising a recording magnetic layer formed on a non-magnetic substrate having an uneven pattern,
When the concave portion and the convex portion of the recording magnetic layer are magnetized in opposite magnetization directions, the current value range determined by the amplitude allowable range on the magnetization current dependence characteristic diagram of the reproduction waveform in the concavo-convex pattern is Iam.
When the range of current values determined by p0 to Iamp1 and the time allowable range is Iint0 to Iint1, Iamp0 or Iint0, whichever is smaller, is set as the lower limit of the magnetizing current, and Iamp1 or Iint1
The magnetizing method is characterized in that the magnetizing method is performed by using the larger one of the two as the upper limit of the magnetizing current. 2. A magnetic disk comprising a recording magnetic layer formed on a non-magnetic substrate on which an uneven pattern is formed,
A magnetic disk in which the concave portion and the convex portion of the recording magnetic layer are magnetized in opposite magnetization directions by the magnetizing method according to claim 1.