JPH10308021A - Record medium master disk and record medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deformation such as wavy parts on the surface of a substrate by forming a master disk made of Ni so as to have a shape corresponding to the surface shape of the substrate formed in one direction surface and have its thickness more than a specified dimension. SOLUTION: A recessed and projecting pattern formed in one direction surface of a master disk 1 is formed according to the shape of a substrate to be formed, and its thickness is set to a dimension t1 of >= about 0.4 mm. The strength of this master disk 1 itself is increased if t1 is >= 0.4 mm, but about 0.4 mm is desirable from the viewpoint of a manufacturing process. If the thickness of the master disk 1 is set >=0.5 mm, uneven thickness occurs in a surface during manufacturing and, as the thickness is larger, unevenness is increased and thus it is more difficult to suppress such unevenness. The master disk 1 is formed so as to have a mirror-like surface if a substrate to be formed is a mirror type.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording medium master for forming a substrate and a recording medium having a substrate formed from the recording medium master. More specifically, the present invention relates to a recording medium having a magnetic layer formed on at least one surface thereof, The present invention relates to a recording medium master for forming a substrate constituting a magnetic disk on which address signals and the like are recorded by a magnetic head or the like, and a recording medium having this substrate.

[0002]

2. Description of the Related Art For example, in a computer system, a hard disk device is used as a magnetic disk recording / reproducing device for recording / reproducing a magnetic disk. Magnetic films are formed on both surfaces of a magnetic disk built in the hard disk device. In this magnetic disk, at the time of recording and reproduction, information signals and the like are concentrically recorded and reproduced on a magnetic film by a magnetic head mounted on a flying head slider.

In recent years, in such a hard disk device, it has been desired to reduce the size of the device itself and increase the capacity of recording signals. Means for achieving these are to improve the positioning accuracy of the magnetic head, that is, the tracking accuracy. As a method for improving the tracking accuracy in this way, there are various tracking servo systems.

[0004] As a normal tracking servo system,
A method is adopted in which a tracking signal recorded on a magnetic disk is reproduced by a magnetic head, and the position of a head slider is controlled based on the reproduced tracking signal to position the magnetic head at the center on a track.

The tracking accuracy of the tracking servo system varies depending on the accuracy of recording a tracking signal on a magnetic disk by a magnetic head. Therefore, in order to improve the tracking accuracy, a high-precision head feed mechanism for recording a tracking signal is required.

However, since the head feed mechanism is of a mechanical type, its accuracy is limited, and there has been a problem that a desired hard disk drive cannot be downsized and a large recording capacity cannot be achieved.

Therefore, in order to solve such a problem,
A data recording area (hereinafter, referred to as a data zone) including an uneven portion and a control signal recording area (hereinafter, referred to as a servo zone) are formed on both surfaces of the magnetic disk in advance.
A so-called pre-emboss type magnetic disk has been developed.

The pre-emboss type magnetic disk has a substrate made of glass, aluminum, or the like, and having a surface with irregularities. As described above, this magnetic disk has a data zone where information signals are recorded and a servo zone where control signals are recorded.

In the data zone, the data track is formed so as to be convex, and a guard band for separating adjacent data tracks is formed so as to be concave.

In the servo zone, servo patterns such as a burst portion serving as a reference for generating a servo lock, an address portion for specifying a data track, and a fine pattern portion for tracking control of a magnetic head are projected. It is formed so as to be a part or a concave part.

[0011] These data zone and servo zone are:
When an annular substrate is molded by an injection molding method, the substrate is transferred and molded between an outer peripheral edge and an inner peripheral edge of the substrate by a stamper attached to a molding die. In the data zone and the servo zone formed on the substrate, a magnetic film is formed on the surface, and signals are recorded so that the concave portions and the convex portions have opposite polarities.

In such a magnetic disk, since a servo pattern is formed on the surface of the substrate by forming an uneven portion in advance, the accuracy of tracking depends on the accuracy of patterning of the uneven portion. Further, since the uneven portion is patterned using photolithography or the like, the accuracy of the patterning can be improved to be higher than the accuracy of the conventional head feeding mechanism. Therefore, the magnetic disk on which the servo pattern is formed can achieve a smaller hard disk drive and a larger recording capacity.

Conventionally, a substrate constituting a pre-embossed magnetic disk on which a concavo-convex pattern has been previously patterned as described above is mounted on a mold with a stamper patterned in a shape opposite to the concavo-convex pattern formed on the substrate. ,
It is formed by injection molding with a synthetic resin or the like.

This stamper is made of N from the viewpoint of productivity.
It is produced by forming a plating made of i. The stamper is usually used with a thickness of about 0.3 mm.

[0015]

By the way, a magnetic disk substrate manufactured by injection molding using a synthetic resin has a simpler manufacturing process and can be manufactured in large quantities at a lower cost than those made of glass or aluminum. It is.

In particular, from the viewpoint of the manufacturing process, in the case of a pre-emboss type magnetic disk substrate in which unevenness is formed on the substrate, the process of performing pre-emboss type patterning on an aluminum substrate or a glass substrate is complicated and technical. Therefore, it is effective to produce by injection molding using a synthetic resin.

However, when the above-described stamper is attached to a mold and injection molding is performed, the stamper is pressed against the mold at a high temperature and a high pressure due to the pressure when the pair of molds are clamped. Non-uniformity of the surface is reflected on the stamper side, and the stamper itself is deformed by undulation due to high temperature and high pressure. The cause of the deformation of the stamper is mainly the lack of rigidity of the stamper itself. In addition, the pressure at the time of mold clamping at the time of injection molding is about 130 kg per square centimeter.
It is about.

When glass or aluminum is used as the magnetic disk substrate, the step of smoothing the substrate surface is performed by polishing the surface of the substrate. On the other hand, in the case of a substrate made of a synthetic resin, since there is no step of smoothing the substrate surface as described above, the problem of distortion on the substrate surface is further increased.

Here, in a read-only optical disk or a magneto-optical disk on which information signals are recorded by forming embossed pits on the surface, a substrate made of a synthetic resin is similarly used. A substrate is used in which waviness is formed at intervals of about several mm to several tens of mm in the radial direction and at a depth of about several tens to several hundreds of nm. Even when recording / reproducing is performed using an optical pickup, in a magneto-optical disk or the like, a servo zone may be sufficient, and deformation of a substrate or the like hardly causes a problem.

However, when a substrate made of a synthetic resin produced by an injection molding method is used as a substrate for a magnetic disk, the flatness of the substrate is a very important factor, which poses a serious problem.

For example, when recording / reproducing a magnetic disk, the head slider is moved from the surface to about 40 nm to 80 nm.
Since recording / reproducing is performed while flying on the order of nanometers, deformation of the substrate or the like adversely affects the flying characteristics of the head slider and causes a fluctuation in flying height. Subtle spacing fluctuations that occur between the magnetic head mounted on such a head slider and the surface of the magnetic disk adversely affect the recording and reproduction of signals by the magnetic head, causing tracking errors and the amplitude of recording and reproduction signals. Cause fluctuations. Furthermore, if the surface of the magnetic disk is not flat, the surface of the magnetic disk may collide with the magnetic head.

The present invention has been proposed in view of the above-described circumstances, and uses a recording medium master that does not cause deformation such as undulations on the surface of a substrate, and a method using the recording medium master. An object is to provide a manufactured recording medium.

[0023]

Means for Solving the Problems The inventor of the present invention has conducted studies to solve the above-mentioned problems, and as a result, the conventional recording medium master has undulations and irregularities due to heat or the like at the time of molding the substrate. It has been found that undulations, irregularities, and the like occur on the molded substrate. The recording medium master according to the present invention completed on the basis of such knowledge is made of Ni, has a shape corresponding to the surface shape of the substrate to be formed on one surface, and has a thickness of 0.4 mm or more. It is characterized by the following.

Since the thus configured recording medium master has a thickness of about 0.4 mm or more, it is possible to increase the rigidity of the recording medium master itself as compared with the conventional recording medium master. it can. Therefore, this recording medium master has little deformation, undulation, etc., even when subjected to high temperature and high pressure during substrate molding.

The recording medium according to the present invention uses a recording medium master having a shape corresponding to the surface shape of the substrate to be molded on one side and having a thickness of 0.4 mm or more. It is characterized by having a molded substrate.

Since the recording medium thus configured has a thickness of about 0.4 mm or more, its surface shape is transferred by a recording medium master having little deformation and undulation even under high temperature and high pressure. Therefore, the deformation of the recording medium master disc itself is not transferred.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a recording medium master and a recording medium according to the present invention will be described in detail with reference to the drawings.

The recording medium master and the recording medium according to the present invention have a magnetic layer formed on the surface, for example, and a disk master for forming a substrate constituting a magnetic disk on which information signals, address signals, etc. are recorded and reproduced by a magnetic head or the like. Further, the present invention can be applied to a magnetic disk having a disk substrate formed by the disk master.

As shown in FIG. 1, the master disc 1 is made of Ni, and has an uneven pattern on one surface 1a. The concavo-convex pattern formed on one surface 1a of the disk master 1 is formed according to the shape of the substrate to be formed. The master disc 1 has a thickness t ₁ of about 0.1.
It is formed so as to be 4 mm or more. It should be noted that when the substrate to be molded is a mirror-type substrate, the disk master 1 has a mirror surface. Also, this disc master 1
If the thickness t ₁ is 0.4 mm or more, the strength of the disc master itself can be increased. However, from the viewpoint of the manufacturing process, it is desirable that the thickness be about 0.4 mm. The master disc 1 has a thickness of about 0.5 mm.
In this case, thickness unevenness occurs on the surface during manufacturing, and the thicker the thickness, the greater the unevenness, and it is difficult to suppress the unevenness. Therefore, it is desirable that the master disc 1 has a thickness of about 0.5 mm or less.

Next, the structure of the master disk 1 will be described in detail by describing an example of a manufacturing method.

The method of manufacturing the disk master 1 includes a polishing step of polishing one surface of a glass master made of a glass material,
A resist layer forming step of forming a resist layer on a glass master, an exposure step of exposing the resist layer with laser light, a developing step of developing the resist layer exposed by laser light, and a Ni layer on the resist layer. Ni to form
The method includes a layer forming step and a disk master mounting step of mounting a disk master made of Ni to a mold.

First, in the polishing step, as shown in FIG. 2, a glass master 2 is manufactured by polishing one surface of a glass plate made of a glass material. The glass master 2 polished in this polishing step is polished on one side, so that a resist is applied in a later step.

Next, in a resist layer forming step, as shown in FIG. 3, a resist layer 3 which becomes alkali-soluble by exposure treatment is formed on the glass master 2.

Next, in the exposure step, as shown in FIG.
And condensing it for exposure. At this time, while rotating the glass master 2, the laser light focused on the glass master 2 is sent in the radial direction at an equal distance per rotation. In this manner, by exposing the laser beam, the latent image of the groove is formed in the resist layer 3 in a spiral shape at a fixed track pitch. At this time, by irradiating the laser light intermittently, a latent image such as a land and a groove or an embossed pit is formed on the resist layer 3. When a mirror-type master disk having a mirror-finished surface is manufactured, the above-described resist layer forming step, this exposing step, and the developing step described below are not performed.

Next, in the developing step, the glass master 2 is developed with an alkaline developer to remove the portion exposed by the laser beam in the above-described step.
As a result, an uneven pattern to be formed on the master disk is formed. In the concavo-convex pattern formed by the resist layer 3, grooves as continuous grooves and lands left between the grooves are alternately formed in the radial direction of the glass master 2.

Next, in the Ni layer forming step, as shown in FIG. 5, a Ni layer 5 made of Ni is formed on the glass master 2 by electroless plating. Here, the Ni layer 5 is
The film is formed with a thickness of about 0.4 mm or more.

Next, in the disk master mounting process,
As shown in FIG. 6, the Ni layer 5 formed on the glass master 2 is separated from the glass master 2. At this time, by removing the extra resist adhering to the Ni layer 5,
A master disk 6 made of a Ni layer 5 is manufactured. And
When a disk substrate is manufactured from the disk master 6 by, for example, an injection molding method, as shown in FIG.
It is attached to a mold 7 constituting an injection molding device.

The method of manufacturing the master disc is not limited to the above-described example of the manufacturing method. A Ni layer is formed on a glass master, and the Ni layer is formed of, for example, a photoresist so as to correspond to the substrate shape. An uneven pattern may be formed, and etching may be performed on the photoresist by ion etching or the like to manufacture a disc master made of Ni having an uneven pattern formed on one surface.

The disk substrate formed from the disk master manufactured in this manner has a surface shape as shown in FIG. Here, FIG. 8 is a diagram in which the vertical axis indicates the depth [nm] of the unevenness on the surface of the disk substrate, and the horizontal axis indicates the position [mm] in the circumferential direction of the disk substrate. The disk master used here had a Ni layer formed to about 0.4 mm.

The relationship between the depth [nm] of the irregularities on the surface of the disk master or the disk substrate and the position [mm] in the circumferential direction of the disk master or the disk substrate described below is determined by a needle-type surface shape inspection apparatus. , And the shape of the concavo-convex pattern corresponding to the information signal or the like formed on the surface is removed. That is, the relationship between the depth [nm] of the unevenness of the surface of the disk master or the disk substrate and the position [mm] in the circumferential direction of the disk master or the disk substrate is an extra pattern other than the uneven pattern formed on the disk master or the disk substrate. Undulations and undulations. Further, the relationship between the depth [nm] of the unevenness on the surface and the position [mm] in the circumferential direction has a curved characteristic.
This is undulation caused by fixing the disk master or the disk substrate to the surface shape inspection device, and is different from the undulation of the disk master or the disk substrate itself.

As shown in FIG. 8, the disk substrate formed by transferring the concavo-convex pattern formed on the disk master as described above has an undulation of about 70 nm as a whole. It can also be seen that the irregularities having a small period are formed at a thickness of about 15 nm or less. Such a disk substrate has a circumference of about 20 mm within about 4 mm.
Although undulation of about nm is generated, if the slider with the magnetic head is about 2 mm in the circumferential direction of the disk substrate, the slider will not be unable to follow the surface shape of the disk substrate. .

Next, FIG. 9 shows a surface shape of a disk substrate formed by a disk master manufactured with the Ni layer 7 having a thickness of about 0.5 mm in the above-described disk master manufacturing process.

According to FIG. 9, the thickness is about 0.5 m.
Even if the disk substrate formed by the disk master formed in about m is formed by the injection molding method, only a slight irregularity is formed in the circumferential direction, and the shape of the disk master is almost exactly correct. You can see that it has been transcribed.

On the other hand, as a comparative example, only Ni was used.
A master disk having a thickness of about 0.3 mm has a surface shape as shown in FIG. It can be seen that the disk substrate injection-molded using such a disk master has irregularities on the surface as shown in FIG. The unevenness has a depth of about 100 nm and occurs at a period of about 2 mm in the circumferential direction. However, on this disk substrate, the concavo-convex pattern of information signals and the like is accurately transferred.

As described above, when recording / reproducing a magnetic disk having a disk substrate in which irregularities having a depth of about 100 nm are generated at a cycle of about 2 mm, about 2 mm in the circumferential direction. This is performed by a magnetic head provided on a slider having a length dimension. As described above, when recording / reproducing is performed by floating the slider having a length of about 2 mm in the circumferential direction on the magnetic disk, the amplitude is large due to irregularities having a period of about 2 mm formed on the disk substrate. Therefore, the slider cannot follow.
That is, recording and reproduction of information signals, address signals, and the like are not performed in portions where such irregularities occur.

Therefore, according to the master disk manufactured with the thickness dimension of about 0.4 mm or more, as described above, there is no unevenness that makes it impossible to record and reproduce information signals, address signals, and the like. It is possible to form a disk substrate that does not cause the failure to be performed.

Next, a magnetic disk manufactured by using the above-described disk master will be described.

As shown in FIG. 12, the magnetic disk 20 has a magnetic layer and the like formed on a disk substrate formed by an injection molding apparatus having a disk master manufactured by the above-described process. And address signals are recorded. The magnetic disk 20 has a data zone 21 for recording information signals and a servo zone 22 for recording address signals and the like.

The data zone 21 includes a data track portion 23 in which concavo-convex patterns are formed concentrically on the magnetic disk 20 and signal information formed in a convex shape is recorded, and a guard band portion 24 formed in a concave shape. A recess is formed. The recording and / or reproduction of the information signal is performed by following the floating magnetic head to the data zone 21.

The data track portion 23 is formed by a convex portion formed on the surface of the disk substrate. The data track portion 23 has a predetermined track pitch by being formed of a convex portion. A magnetic layer is formed on the data track portion 23, and information signals are recorded by changing the magnetization direction of the magnetic layer. The data track section 23 is reproduced by detecting a leakage magnetic field corresponding to a recorded information signal by a magnetic head.

The guard band portion 24 is formed by a concave portion between the data track portions 23. Although a magnetic layer is formed in the guard band portion 24, since the magnetic layer is recessed from the data track portion 23, a spacing loss occurs between the guard band portion 24 and the magnetic head, and recording of information signals and the like is almost impossible. Not done. Therefore, the guard band 2
4 functions to reduce the recorded noise component by the leakage magnetic field generated from the side surface of the head gap when the information signal is recorded by the magnetic head, and has an advantage of improving the SN ratio. I have.

As shown in FIGS. 13 and 14, the servo zone 22 is a concavo-convex portion formed radially from the center of the magnetic disk 20, and a plurality of concentrically arranged data track portions 23 divided from each other. Of sectors. This sector is formed by dividing the data track portion 23 substantially vertically by unevenness, and a predetermined amount of information signal is recorded.

The servo zone 22 includes a burst section 25 serving as a reference for generating a servo lock, an address section 26 for specifying a data track section 23, and a fine pattern section 27 for controlling tracking of a magnetic head. Are formed so as to be concave portions or convex portions. In the servo zone 22, a magnetic layer is formed on the surface of the formed disk substrate, and signals of opposite polarities m1 and m2 indicated by arrows in FIG. 13 are recorded in the concave and convex portions. That is, the servo zone 22 has a function of causing the magnetic head to accurately follow the data track section 23.

FIG. 15 shows a reproduced signal waveform of a servo signal recorded on the servo zone 22 of the magnetic disk 20 as described above. In FIG. 15, the horizontal axis represents time [μsec].
And the vertical axis represents the voltage value [mV] of the reproduction signal waveform. According to FIG. 15, it can be seen that the magnetic disk 20 having the above-described disk substrate reproduces the servo signal with a substantially constant amplitude and a constant period. In addition,
The magnetic disk 20 has a disk substrate formed using a disk master made of Ni and having a thickness of about 0.5 mm. The magnetic disk 20
It is considered that the same reproduced signal can be obtained even with a disk substrate made of Ni and formed using a disk master having a thickness of about 0.4 mm.

On the other hand, as a comparative example, a reproduced signal of a servo signal recorded on a servo zone of a magnetic disk having a disk substrate formed of a Ni and having a thickness of about 0.3 mm and having a disk substrate. The waveform is shown in FIG. According to FIG. 16, it can be seen that the servo signal does not have a constant amplitude and a constant cycle. In such a magnetic disk, there is a possibility that accurate tracking of the magnetic head or the like cannot be performed.

Therefore, the magnetic disk 2 having the disk substrate formed by the disk master as described above.
A value of 0 does not mean that the period of the irregularities on the surface is smaller than the circumferential length of the slider flying above the surface, so that the slider cannot follow. Therefore,
According to the magnetic disk 20, there is no possibility that the signal cannot be reproduced due to the unevenness formed on the surface.

In the above description, a disk master for forming a substrate on which information signals and address signals are formed as a concavo-convex pattern on the surface and a magnetic disk having a substrate formed from the disk master have been mainly described. The recording medium master and the recording medium according to the present invention can also be applied to a mirror disk master for forming a mirror-type substrate having a mirror-finished surface and a magnetic disk having a mirror-type substrate formed from the disk master. Of course, it is.

In the above description, an example in which the recording medium master and the recording medium according to the present invention are applied to a disk master and a magnetic disk has been described. It is needless to say that the present invention can be applied to a recording medium master for molding a substrate made of a synthetic resin or the like constituting a disk or the like and a recording medium manufactured using the recording medium master.

[0059]

As described in detail above, since the recording medium master according to the present invention has a thickness of about 0.4 mm or more, the strength of the recording medium master itself can be improved. is there. Therefore, according to the recording medium master, even when the recording medium substrate is formed by injection molding, unevenness and undulation due to high temperature and high pressure do not occur.
Therefore, according to this recording medium master, it is possible to mold a recording medium substrate having no irregularities or undulations on the surface. Therefore, the substrate formed by the recording medium master has, for example, a magnetic layer formed on the surface, and can perform recording / reproduction by a magnetic head that records / reproduces signals with a low flying height. Can be realized.

Further, since the recording medium according to the present invention has a substrate formed by a recording medium master having a thickness of about 0.4 mm or more, deformation or undulation of the recording medium master is transferred to the surface. There is nothing. Therefore, according to this recording medium, information signals and address signals are not prevented from being recorded or reproduced due to irregularities or undulations on the surface of the substrate, and high density of information signals and the like can be realized. It is possible.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of a master disc to which the present invention is applied.

FIG. 2 is a cross-sectional view showing an example of a glass master.

FIG. 3 is a cross-sectional view showing an example of a state where a resist layer is formed on a glass master.

FIG. 4 is a cross-sectional view showing an example of a state in which a resist layer is exposed to laser light.

FIG. 5 is a cross-sectional view showing an example of a state where a Ni layer is formed on a resist layer.

FIG. 6 is a cross-sectional view showing an example of a state in which a disk master made of a Ni layer is peeled from a glass master.

FIG. 7 is a diagram showing an example of a state in which a master disc is attached to a mold of an injection molding apparatus.

FIG. 8 is a diagram showing the relationship between the depth of the unevenness and the position in the circumferential direction of a disk substrate formed by a disk master made of a Ni layer having a thickness of about 0.4 mm.

FIG. 9 is a diagram showing the relationship between the depth of irregularities and the position in the circumferential direction of a disk substrate formed by a disk master made of a Ni layer having a thickness of about 0.5 mm.

FIG. 10 is a diagram showing the relationship between the depth of irregularities and the position in the circumferential direction of a disk master made of a Ni layer having a thickness of about 0.3 mm.

FIG. 11 is a diagram showing the relationship between the depth of irregularities and the position in the circumferential direction of a disk substrate formed by a disk master made of a Ni layer having a thickness of about 0.3 mm.

FIG. 12 is a plan view showing an example of a magnetic disk to which the present invention is applied.

FIG. 13 is a plan view showing an example of a servo zone of the magnetic disk.

FIG. 14 is a sectional view showing an example of a servo zone of the magnetic disk.

FIG. 15 is a diagram showing an example of a reproduction signal of a servo zone of the magnetic disk.

FIG. 16 is a diagram showing a reproduction signal of a servo zone of a conventional magnetic disk.

[Explanation of symbols]

1 master disk, 5 Ni layer, 20 magnetic disks,
21 data zone, 22 servo zone

Claims (8)

[Claims] 1. A recording medium master comprising Ni, one surface of which has a shape corresponding to the surface shape of a substrate to be formed, and a thickness dimension of 0.4 mm or more. 2. The recording medium master according to claim 1, wherein an uneven pattern corresponding to a signal recorded on the recording medium is formed on the one surface. 3. The recording medium master according to claim 1, wherein said one surface is a mirror surface. 4. Recording of an information signal by a magnetic head and / or
3. The recording medium master according to claim 1, wherein a substrate constituting a magnetic disk to be reproduced is formed. 5. A recording medium having a substrate formed using a recording medium master made of Ni having a thickness of 0.4 mm or more. 6. The recording medium according to claim 5, wherein a concavo-convex pattern corresponding to a signal is formed on at least one surface of said substrate. 7. The recording medium according to claim 5, wherein at least one surface of said substrate is a mirror surface. 8. The recording medium according to claim 5, wherein the recording medium is a magnetic disk on which a magnetic layer is formed on at least one surface of the substrate and on which information signals are recorded and / or reproduced by a magnetic head.