JPH10222944A - Magnetic recording medium, magnetic recorder/ reproducer and production of disc molding die - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance off-track characteristics by specifying the ratio Lw/Gw of the width Gw of a groove to the width Lw of land, i.e., the protruding part between grooves, formed along a recording track and provided with a pit corresponding to a servo signal thereby suppressing fluctuation in the floating amount of a magnetic head at the time of recording/reproduction. SOLUTION: Lw/Gw is set at 2.0 or above. In one embodiment of a magnetic disc where a magnetic recording layer is formed on a disc substrate of 2.5" diameter, the level difference between a groove 3 and a land 4, i.e., a data zone, is 100nm, the width t1 of the upper surface of the data zone 4 is 2.3μm, the width t3 of inclining surface part on the boundary of the data zone 4 and the groove 3 is 0.3μm, the width t2 of the bottom face of the groove 3 is 0.9μm. In this regard, the data zone 4 has width Lw=t1 +t3 equal to 2.6μm, the groove 3 has width Gw=t2 +t3 equal to 1.2μm and the ratio Lw/Gw is equal to 2.17.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium in which a groove serving as a guide groove for tracking control is formed, and a magnetic recording / reproducing apparatus for recording / reproducing on / from such a magnetic recording medium. Further, the present invention relates to a method for manufacturing a disk molding die which is a master disk of a substrate of a magnetic recording medium.

[0002]

2. Description of the Related Art In the field of magnetic recording media, development of magnetic recording media in which pits corresponding to servo signals are formed in advance has been promoted in order to further increase the recording density.
Here, the pits corresponding to the servo signals are irregularities formed in advance at the time of molding the substrate of the magnetic recording medium according to the servo signals.

[0003] In a magnetic recording medium having such pits formed thereon, before being used for recording / reproducing, the concave and convex portions are magnetized so that the polarities are opposite, thereby writing a servo signal. . Since such pits can be easily formed very finely and with high precision, by forming pits corresponding to the servo signals in advance on the substrate in this way, it is possible to write servo signals with high precision. It becomes possible. That is, a servo signal can be written at a very accurate position on a recording track, and as a result, high-density recording can be easily achieved as compared with a conventional magnetic recording medium. In the following description, an area where such a servo signal is written is referred to as a servo zone.

In a magnetic recording medium in which such pits are formed, grooves are usually formed along recording tracks. Here, the groove is a groove-shaped recess formed along the recording track, and is formed in a region other than the servo zone. That is, the groove is formed along an area of the recording track where data is recorded and reproduced by the user. The protrusions between the grooves are called lands, and data recorded and reproduced by the user is mainly recorded on the lands. In the following description, an area in which such a groove is formed and data is recorded and reproduced by a user is referred to as a data zone.

[0005]

When recording and reproducing on a magnetic recording medium using a magnetic head, the magnetic head is arranged on the magnetic recording medium and the magnetic recording medium is rotated at a high speed. At this time, the magnetic head slightly flies due to the influence of the flow of air generated by the rotation. In order to perform stable recording and reproduction on the magnetic recording medium, it is desirable to keep the flying height constant.

However, in the magnetic recording medium in which pits and grooves are formed as described above, it is difficult to keep the flying height of the magnetic head constant because the medium surface has irregularities. In particular, in a magnetic recording medium having a servo zone and a data zone, the ratio of the convex portion to the concave portion in the servo zone where the pit is formed, and the ratio of the convex portion and the concave portion in the data zone where the groove is formed. Is different from the flying height of the magnetic head on the servo zone and the flying height of the magnetic head on the data zone.

Here, the height of the pit is equal to or higher than the height of a texture formed on a recording medium in a conventional hard disk device or the like, and the size of the pit is about several μm. It is comparable to texture. Therefore, the magnetic recording medium in which the ratio of the convex portion to the concave portion in the servo zone where the pit is formed is different from the ratio of the convex portion and the concave portion in the data zone where the groove is formed, has a texture. It is in a state where it is formed unevenly.

As a result, as described above, the flying height of the magnetic head on the servo zone is different from the flying height of the magnetic head on the data zone, and the flying height of the magnetic head fluctuates during recording and reproduction. It is difficult to perform stable recording and reproduction. Such a problem is a problem peculiar to a magnetic recording medium in which pits are formed in advance,
This cannot happen with a magnetic recording medium that is flat over the entire surface. That is, in a magnetic recording medium in which pits and grooves are formed in advance, it is a major problem to suppress the fluctuation of the flying height of the magnetic head.

[0009] In a magnetic head in which a groove is formed to make the data zone uneven, the flying height of the magnetic head changes due to the effect of the unevenness, and the off-track characteristic also changes greatly. This can easily be imagined from the fact that the distance from the magnetic head becomes large and the output becomes small in the groove portion which is the concave portion. Therefore, it is necessary to prevent the off-track margin from being reduced by the influence of the groove in a magnetic head in which the data zone is formed by forming a groove.

The present invention has been proposed in view of the above-described conventional circumstances, and is directed to a magnetic recording medium in which pits corresponding to servo signals are formed and grooves are formed along recording tracks. Therefore, a variation in the flying height of the magnetic head during recording and reproduction is small, and it is possible to provide a magnetic recording medium having excellent off-track characteristics, and it is preferable to perform recording and reproduction on such a magnetic recording medium. It is an object of the present invention to provide a magnetic recording / reproducing device. Another object of the present invention is to provide a method for manufacturing a disk molding die suitable for manufacturing a substrate of a magnetic recording medium as described above.

[0011]

When data is recorded on or reproduced from a magnetic recording medium by a floating magnetic head, the relationship between the recording / reproducing characteristics and the flying height of the magnetic head can be obtained by calculation. For example, Williams-Com
“An Analytical Model of theWrite Pro by stock et al.
cess in Digitak Magnetic Recording ”17th Annu. AIP
As described in Conf. Proc. Part 1, 738-742, 1990, the amount of spacing when data is recorded on a magnetic recording medium by a floating magnetic head, that is, the space between the magnetic head and the magnetic recording medium. It is possible to calculate the transition width of the magnetization of the magnetic recording medium based on the distance, and from this, it is possible to estimate the output when reproducing the recorded signal.

That is, by such a calculation, it is possible to know the magnitude of the output of the reproduction signal obtained from an arbitrary position on the magnetic recording medium even if the magnetic recording medium has pits or grooves formed thereon. It is possible. Therefore,
For example, a ratio between a reproduced signal from a track on which data is newly recorded and a signal serving as noise can be obtained.
Here, the signal serving as noise includes, for example, a signal from a track adjacent to a track on which new data is recorded,
This is a signal or the like caused by old data remaining on the track on which data is recorded. The present inventor has studied the relationship between the ratio of the reproduced signal to the noise and the shape of the pits and grooves, etc., for the magnetic recording medium on which pits and grooves have been formed by such calculations.

By the way, the output of the reproduced signal obtained from the magnetic recording medium is, of course, the largest at the convex portion, and then at the step between the convex and concave portions. Is large and the output from the concave part is the smallest, but when examining the recording and reproduction characteristics,
It is necessary not only to consider the magnitude of the output obtained from each of these parts, but also to examine whether the reproduced output is a proper signal capable of reproducing data. Therefore, as described later, the present inventor manufactured a plurality of magnetic recording media having different shapes of pits and grooves, actually measured their bit error rates, and set conditions under which the bit error rates were sufficiently reduced. Examined.

As a result of the above study, the present inventor has found that, in a magnetic recording medium in which pits and grooves are formed, the off-track characteristics are as follows: the land width Lw, which is a protrusion between grooves, and the groove width Lw. It has been found that the off-track characteristic can be improved by setting the ratio Lw / Gw to an appropriate value.

The present invention has been made on the basis of such findings. In the magnetic recording medium according to the present invention, irregularities corresponding to servo signals are formed, and grooves are formed along recording tracks. And the width L of a land which is a convex portion between the grooves.
The ratio Lw / Gw of w to the width Gw of the groove is 2.0 or more. Here, when the track pitch is Tp and the width of the slope portion at the boundary between the land and the groove is t, the ratio Lw / Gw
Is preferably in the range represented by the following formula (1-1), and specifically, the ratio Lw / Gw is preferably 7.26 or less. It should be noted that such a definition of the ratio Lw / Gw is particularly suitable for a magnetic recording medium in which the step between the groove and the land is 100 nm or more.

Lw / Gw ≦ (4/5 × Tp + t) / (1/5 × Tp-t) (1-1) On the other hand, the magnetic recording / reproducing apparatus according to the present invention has a groove along a recording track. A recording magnetic head for performing magnetic recording on the magnetic recording medium on which is formed, the track width T of the recording magnetic head is not less than the width Lw of a land which is a convex portion between the grooves, Track pitch T
It is characterized by being equal to or less than the sum of p and the width Gw of the groove.

Here, assuming that the land width is Lw, the groove width is Gw, the track pitch is Tp, and the servo error margin during magnetic recording is Em, the track width T of the recording magnetic head is It is preferable to be within the range shown by the following formula (1-2).

Lw + Em × 2 ≦ T ≦ Tp + Gw−Em × 2 (1-2) Further, the method of manufacturing a disk molding die according to the present invention is characterized in that a metal material is adhered on a base material to form a metal film. Forming a pit and / or groove by applying a photoresist on the metal film formed in the metal film forming step, and exposing and developing the photoresist according to a predetermined pattern. A cutting step of forming a resist pattern leaving only a corresponding portion, and performing reactive ion etching on the metal film using the photoresist left in the cutting step as a mask, and forming the pits of the photoresist in the metal film. And / or an etching step of forming a portion corresponding to the groove equivalent portion into a convex shape to form a disk molding die. .

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings. It should be noted that the present invention is not limited to the following examples, and it is needless to say that materials, shapes, and the like can be arbitrarily changed without departing from the gist of the present invention.

The magnetic recording medium according to the present embodiment is a magnetic disk in which a magnetic recording layer is formed on a 2.5-inch-diameter disk substrate made of plastic, and as shown in FIG. It has a servo zone 2 in which a pit 1 is formed and a data zone 4 in which a groove 3 is formed along a recording track. In FIG. 1, black portions indicate convex portions, and other portions indicate concave portions.

The magnetic disk is magnetized so that its concave and convex portions have opposite polarities before recording and reproducing. As a result, a servo signal is written to the pit 1 formed in the servo zone 2.

In this magnetic disk, grooves 3 are formed at a predetermined track pitch Tp in the data zone 4, as shown in FIG. 2, which is a cross-sectional view taken along line AA of FIG. A hill-shaped area between the groove 3 and the groove 3 becomes a land 4. Here, the groove 3 is formed so as to step t ₀ of the groove 3 and the land 4 is equal to or greater than 100 nm. In this magnetic disk, land 4
Is the center of the track, and the data signal is
Is recorded around the part.

In the magnetic disk to which the present invention is applied, the ratio Lw of the width Lw of the land 4 to the width Gw of the groove is obtained.
/ Gw is 2.0 or more. Here, it is difficult to form the land 4 and the groove 3 completely in a rectangular shape, and usually, as shown in FIG. 2, the boundary between the land 4 and the groove 3 is a slope. Therefore, in the following description, as shown in FIG. 2, the width of the upper surface portion of the land 4 is t ₁ , and the width of the groove 3 is
Width t ₂ bottom portion of the width of the slant portion at the boundary of the land 4 and groove 3 and t _3, the land 4 and groove 3
The center of the slope at the boundary of is the boundary between the land 4 and the groove 3. That is, in this specification, t ₁ + t ₃ is referred to as the width of the land 4, the width of the land 4 is referred to as Lw, and t ₂ + t ₃ is referred to as the width of the groove 3.
Is defined as Gw.

For the magnetic disk as described above, the ratio Lw / Gw of the width Lw of the land 4 to the width Gw of the groove 3
A plurality of magnetic disks were manufactured by changing the width Lw of the land 4 and the width Gw of the groove 4 in order to examine the relationship between the magnetic disk and the off-track characteristics.

Here, the concavo-convex pattern of the disk substrate is
The optical disk was formed using the same method as that generally used in the production of the optical disk. That is, first, a photoresist was applied to the surface of a glass substrate serving as a reference surface, and a groove pattern was exposed on the photoresist based on cutting data. After exposing the groove pattern, the photoresist was developed to form a resist pattern corresponding to the groove pattern. next,
Ni plating is performed on the resist pattern, and then the Ni plating is peeled off from the resist pattern,
The back surface was polished to a desired thickness. This is the disk molding die that serves as the master of the disk substrate. Then, injection molding was performed using this disk molding die to produce the disk substrate as described above.

However, in manufacturing the disk substrate in this manner, the groove 3 is not formed over the entire surface of the disk substrate, but is formed at a radius of 20.degree.
It was formed only in the portion between 0 mm and 25.0 mm, and the other portions remained flat.

In the evaluation of the off-track characteristic described later, the off-track characteristic of the magnetic disk on which the groove 3 was formed was measured at a radius of 24.0 mm. In the evaluation of the off-track characteristic described later, the off-track characteristic is compared with the off-track characteristic of a flat magnetic disk. Important part, that is, the radius of the disk substrate 2
It was substituted by examining the off-track characteristics in a portion other than between 0.0 mm and 25.0 mm.

Then, a magnetic recording layer was formed on the disk substrate manufactured as described above by a sputtering method using Ar as a sputtering gas. Here, the magnetic recording layer includes an underlayer serving as an underlayer of the magnetic layer, a magnetic layer including a 0.5 mm-thick intermediate layer made of Cr in the middle, and a protective layer for protecting the magnetic layer. , In this order. Then, a lubricant layer was further formed on such a magnetic recording layer to obtain a magnetic disk.

Specifically, the underlayer was formed by forming a Cr film to a thickness of 10 nm at a sputtering gas pressure of 0.1 Pa and a film formation rate of 2 nm / sec. The magnetic layer was formed by depositing Co ₆₄ Pt ₂₀ Cr ₁₆ to a thickness of 24 nm at a sputtering gas pressure of 0.1 Pa and a deposition rate of 2 nm / sec.
Further, the protective layer was formed by forming a film of C to a thickness of 13 nm at a sputtering gas pressure of 0.5 Pa and a film formation rate of 0.5 nm / sec. Further, the lubricant layer is made of FomblinZ-Do.
1 was formed by a dipping method so that the film thickness became about 2 nm.

When the magnetic characteristics of the magnetic recording layer of the magnetic disk manufactured as described above were measured using a vibrating sample magnetometer (VSM), the residual magnetization thickness Mr · t = 9 mA was maintained. The magnetic force Hc was 167 kA / m, and the coercive force squareness ratio S ^* was 0.8.

In order to examine the characteristics of the magnetic disk as described above when the width Lw of the land 4 and the width Gw of the groove 3 are changed, as first to third embodiments, the width Lw of the land 4 and the groove Lw will be described. In addition to producing a magnetic disk having a ratio Lw / Gw of 2.0 or more to the width Gw of the groove 3, the ratio Lw / Gw of the width Lw of the land 4 to the width Gw of the groove 3 was less than 2.0 as a comparative example. Was prepared. In the following Examples and Comparative Examples, numerical values indicating the shapes of the grooves 4 and the lands 3 are the shapes of the grooves 4 and the lands 3 actually formed on the magnetic disk using an atomic force microscope (AFM). Are actually measured values.

Embodiment 1 In the magnetic disk of this embodiment, the step t ₀ between the groove 3 and the land 4 is 100 nm, the width t ₁ of the upper surface of the land 4 is 2.3 μm, and the slope at the boundary between the land 4 and the groove 3 The width t ₃ is 0.3 μm, and the width t ₃ of the bottom surface of the groove ₃ is 0.9 μm. At this time, the width Lw of the land 4 = t ₁
+ T ₃ is 2.6 μm, and the width of the groove 3 Gw = t ₂ +
t ₃ is 1.2 μm, and their ratio Lw / Gw is 2.
Seventeen.

Embodiment 2 In the magnetic disk of this embodiment, the step t ₀ between the groove 3 and the land 4 is 100 nm, the width t ₁ of the upper surface of the land 4 is 2.5 μm, and the slope at the boundary between the land 4 and the groove 3 is The width t ₃ is 0.3 μm, and the width t ₃ of the bottom surface of the groove ₃ is 0.7 μm. At this time, the width Lw of the land 4 = t ₁
+ T ₃ is 2.8 μm, and the width of the groove 3 Gw = t ₂ +
t ₃ is 1.0 μm and their ratio Lw / Gw is 2.
80.

Embodiment 3 In the magnetic disk of this embodiment, the step t ₀ between the groove 3 and the land 4 is 100 nm, the width t ₁ of the upper surface of the land 4 is 2.8 μm, and the slope at the boundary between the land 4 and the groove 3 is formed. The width t ₃ is 0.3 μm, and the width t ₃ of the bottom surface of the groove ₃ is 0.4 μm. At this time, the width Lw of the land 4 = t ₁
+ T ₃ is 3.1 μm, and the width of the groove 3 Gw = t ₂ +
t ₃ is 0.7 μm, and their ratio Lw / Gw is 4.
43.

[0035] In the magnetic disk of Comparative Example 1 In this comparative example, the step t ₀ of the groove 3 and the land 4 is 100 nm, the width t ₁ of the upper surface of the land 4 is 2.0 .mu.m, the ramp portions at the boundary of the land 4 and groove 3 The width t ₃ is 0.3 μm, and the width t ₃ of the bottom surface of the groove ₃ is 1.2 μm. At this time, the width Lw of the land 4 = t ₁
+ T ₃ is 2.3 μm, and the width of the groove 3 Gw = t ₂ +
t ₃ is 1.5 μm and their ratio Lw / Gw is 1.
53.

Evaluation of Off-Track Characteristics Recording and reproduction were actually performed on the magnetic disks manufactured as described above, and their off-track characteristics were measured.

Here, for recording and reproduction, a composite magnetic head combining an inductive magnetic head functioning as a recording magnetic head and a magnetoresistive magnetic head functioning as a reproducing magnetic head was used. A recording magnetic head composed of an inductive magnetic head has a track width of 3.8 μm and a magnetic gap interval of 0.5 μm. A reproducing magnetic head composed of a magnetoresistive magnetic head is used. , Track width is 3.0μ
m, the distance between the magnetic shields sandwiching the magnetoresistive element was 0.36 μm.

The above-mentioned composite magnetic head was used by incorporating it into a so-called 50% nano slider in order to secure a contact with the magnetic disk. Here, the slider length was 2.0 mm and the slider width was 1.6 mm. Recording and reproduction were performed by rotating the magnetic disk at a linear velocity of 7.36 m / sec. At this time, the flying height of the composite magnetic head is about 60 nm.

The measurement of the off-track characteristic is shown in FIG.
As shown in (1), data D1, D2, D3, D4, and D5 were written on a magnetic disk using a recording magnetic head, and then data D3 was reproduced by a reproducing magnetic head 10.

That is, first, as shown at t ₁₁ and t ₁₂ in FIG. 3, each of the right and left tracks is shifted by 1.52 μm from a track for which the off-track characteristic is to be measured (hereinafter, referred to as a recording track). Temporary data D1 and D2 were written to one track using a recording magnetic head.

Next, data D3 to be detected was written on the recording track using a recording magnetic head. At this time, the width t _{13 of} the portion written on the recording track corresponds to the track width T of the recording magnetic head, and is 3.8 μm. The data length of the data D3 recorded on the recording track was 9628 Bytes.

Next, the recording magnetic head was shifted from the center of the recording track by a width corresponding to 95% of the track pitch Tp, and data D4 and D5 were overwritten on two adjacent left and right tracks. That is, t ₁₄ and t in FIG.
_As shown in FIG. ₁₅ , data D4 and D5 were overwritten on two tracks on the left and right, which were separated by 3.6 μm from the center of the recording track, using a recording magnetic head.

Then, the reproducing magnetic head 10 having a track width t ₁₆ of 3.0 μm is repeatedly reproduced with respect to the area in which the data is written as described above while shifting the reproducing magnetic head little by little from the center of the recording track. Data and
The bit error rate was measured by comparing with the original recording data. Here, the standard of the bit error rate was set to 10 ^-7 . That is, the maximum off-track amount that satisfies the bit error rate of 10 ⁻⁷ was used as the evaluation criterion. In the following description, the maximum off-track amount that satisfies the bit error rate of 10 ⁻⁷ is simply referred to as the maximum off-track amount. When the groove 3 is not formed and the disk surface is flat, the maximum off-track amount is about 1.3 μm.
m.

FIG. 4 shows the result of measuring the bit error rate of the magnetic disk manufactured as a comparative example as described above. In FIG. 4, the horizontal axis represents the off-track amount, that is, the position of the maximum off-track amount when the reproducing magnetic head 10 is shifted to the left with respect to the recording track. As shown.

As can be seen from FIG. 4, the maximum off-track amount of the magnetic disk of the comparative example was about 1.28 μm. As described above, in the magnetic disk of the comparative example, the groove 3 is not formed, the maximum off-track amount is smaller than when the disk surface is flat, and the off-track characteristics are deteriorated.

Then, the maximum off-track amount was similarly measured for the magnetic disks manufactured as Examples 1 to 3. FIG. 5 shows the measurement results together with comparative examples in a graph.

In FIG. 5, the horizontal axis represents the width t ₁ of the upper surface of the land 4, and the vertical axis represents the maximum off-track amount. H1 is the magnetic disk of the comparative example, J
Reference numeral 1 denotes the magnetic disk of the first embodiment, J2 denotes the magnetic disk of the second embodiment, and J3 denotes the magnetic disk of the third embodiment.

Since the maximum off-track amount when the disk surface is flat is about 1.3 μm, the off-track characteristics are improved more than when the disk surface is flat, FIG. 5 shows that the width t ₁ is about 2.23 μm or more.

The width t ₁ of the upper surface of the land 4 is 2.23 μm because the width Lw = t ₁ + t ₃ of the land 4 is 2.26 μm.
m, the width Gw = t ₂ + t _{3 of} the groove 3 corresponds to 1.27 μm, and their ratio Lw / Gw is 1.99. That is, when the ratio Lw / Gw is about 2.0 or more, the maximum off-track amount becomes larger than when the disk surface is flat, and the off-track characteristics are improved.

From the above, it has been found that the off-track characteristic is improved when the ratio Lw / Gw of the width Lw of the land 4 to the width Gw of the groove 3 is about 2.0 or more. Is realized only when at least the entire land 4 is covered by the recording magnetic head.
In order for the recording magnetic head to cover the land 4 without fail, the track width T of the recording magnetic head must be larger than the width Lw of the land 4. Therefore,
In a magnetic recording / reproducing apparatus that performs recording / reproducing on a magnetic disk in which the groove 3 is formed, it is necessary to make the track width T of the recording magnetic head larger than the width Lw of the land 4.

On the other hand, as shown in FIG. 6, the track width T of the recording magnetic head 11 is the width Lw of the land 4, the width Gw of the groove 3 formed on the right side of the land 4, and the width of the land 4.
Is larger than the sum of the width Gw of the groove 3 formed on the left side of the track, data will always be written to the land 4 of the adjacent track. Here, the sum of the width Lw of the land 4 and the width Gw of the groove 3 corresponds to the track pitch Tp. Therefore, the track width T of the recording magnetic head 11 needs to be equal to or less than the sum of the track pitch Tp and the width Gw of the groove 3.

In summary, in a magnetic recording / reproducing apparatus provided with a recording magnetic head for performing magnetic recording on a magnetic disk having grooves 3 formed along recording tracks, the track width T of the recording magnetic head is reduced. , The width of the land 4 and the width of the groove 3 are preferably equal to or less than the sum of the track pitch Tp and the width Gw of the groove 3.

Further, considering an actual magnetic recording / reproducing apparatus, if the track width T of the recording magnetic head is the same as the width t ₁ of the upper surface of the land 4, if a servo error occurs in the recording magnetic head during writing, Then, the land 4 cannot be covered immediately. Therefore, in order to cover the land 4 sufficiently, the track width T of the recording magnetic head is set to be slightly larger than the width t ₁ of the upper surface of the land 4 in consideration of a servo error at the time of recording. More specifically, it is preferable to add a width approximately twice as large as a servo error margin at the time of recording to the track width T of the recording magnetic head.

Therefore, when the servo error margin at the time of recording is Em, the track width T of the recording magnetic head is
Preferably satisfies the following expression (2-1).

T ₁ + Em × 2 ≦ T (2-1) On the other hand, if the track width T of the recording magnetic head is too wide,
The track width T needs to be smaller than the sum of the track pitch Tp and the width Gw of the groove 3 because the track enters the land 4 of the adjacent track. Also at this time, it is necessary to take into account the servo error at the time of recording, and the track width T of the recording magnetic head is
It is preferable to satisfy the following expression (2-2).

T ≦ Tp + Gw−Em × 2 (2-2) Therefore, from the above equations (2-1) and (2-2), the track width T of the recording magnetic head is expressed by the following equation (2- It is preferable that the setting is made so as to satisfy 3).

Lw + Em × 2 ≦ T ≦ Tp + Gw−Em × 2 (2-3) By the way, as described above, the recording magnetic head covers the land 4 regardless of the servo error. Has the track width T of the recording magnetic head set to (t ₁ +
Em × 2) or more. In a normal magnetic recording / reproducing apparatus, the servo error margin of the recording magnetic head is approximately 1/10 or less of the track pitch Tp. Therefore, the track width T of the recording magnetic head needs to be (t1 + Tp / 5) or more.

Since the recording magnetic head is not allowed to enter the land 4 of the adjacent track, the recording magnetic head having the track width T of (t1 + Tp / 5) is not used. 7, it is necessary to satisfy the following expression (2-4).

T ₃ + t ₂ + t ₃ ≧ Tp / 5 (2-4) Here, the width Lw of the land 4 is represented by (t ₁ + t ₃ ), and the width Gw of the groove 3 is (t ₂ + t) ₃ ) From the above equation (2-4), the ratio Lw / Gw of the width Lw of the land 4 and the width Gw of the groove 3 needs to satisfy the following equation (2-5). I understand.

Lw / Gw ≦ (4/5 × Tp + t ₃ ) / (1/5 × Tp−t ₃ ) (2-5) In the above example, the track pitch Tp = 3.8 μm
m, and the width t ₃ of the slope at the boundary between the land 4 and the groove 3 is t ₃ = 0.3 μm.
From the ratio L of the width Lw of the land 4 to the width Gw of the groove 3
It is preferable that w / Gw is 7.26 or less.

However, the above equation (2-5) is generally applicable regardless of the value of the track pitch Tp. Therefore, the present invention sets the track pitch Tp to 3.8 μm
However, the present invention is not limited to the above embodiments.

Incidentally, the definition of the ratio Lw / Gw is as follows.
As shown in FIG. 8, an angle θ formed between the slope 101 at the boundary between the land 101 and the groove 102 and the land 101.
Is particularly suitable for a magnetic disk having an angle of 90 ° or more and 105 ° or less. When θ is 90 ° or more and 105 ° or less, a magnetic disk having more excellent off-track characteristics can be obtained.

As will be described later, since the substrate of such a magnetic disk is manufactured by injection molding, θ does not become 90 ° or less. If θ is 105 ° or more, the off-track characteristics deteriorate.

A substrate of a magnetic disk having θ of 90 ° or more and 105 ° or less is manufactured by injection molding using a disk molding die as described below.

The disk molding die comprises a base material and a metal film formed on the base material. The method for manufacturing the disk molding die includes a metal film forming step, a cutting step, and an etching step.

In the metal film forming step, a metal material is applied on the base material to form a metal film, and the surface of the metal film is polished to a mirror surface.

As the metal material, a material having reactivity to ion plasma is preferable.
And so on.

In the cutting step, a photoresist is applied on the metal film formed in the metal film forming step, and the photoresist is exposed and developed according to a predetermined pattern. A resist pattern is formed in accordance with the predetermined pattern, leaving only the pit and groove equivalent portions.

In the etching step, the metal film is subjected to reactive ion etching using the photoresist left in the cutting step as a mask. A portion of the metal film corresponding to the pit and groove equivalent portion of the photoresist is formed in a convex shape to form a disk molding die.

In the above reactive ion etching, BCl ₃
This is a chemical etching in which a reactive gas plasma is used to perform etching by a chemical reaction with a metal of a metal film.

Ti can be etched by a chemical reaction with a gas such as BCl ₃ . When a Ti film is formed on a base material as in the present invention, reactive ion etching can form unevenness more sharply than conventional physical etching in which ions are hit on a metal film and trenches are excavated. it can.

A disk molding die was manufactured by the above method. Using this disk molding die, a disk substrate was produced by injection molding, and a magnetic recording layer was formed on the disk substrate to produce a magnetic disk.

Example 4 First, a Ti film was formed on a substrate by a sputtering method using Ar as a sputtering gas.

Specifically, the degree of vacuum was 5 × 10 ⁻⁵ Pa, the sputtering gas pressure was 0.2 Pa, the input power was 800 W, and the film formation rate was 1
The test was performed under the condition of 0 μm / 3000 s.

Next, a photoresist was applied to the surface of the Ti film which was polished and mirror-finished.

The photoresist was exposed and developed according to a predetermined pattern, thereby forming a resist pattern leaving only the pits and grooves corresponding to the predetermined pattern.

The Ti film was etched using the remaining photoresist as a mask. A portion of the Ti film corresponding to the pit and groove equivalent portion of the photoresist was formed in a convex shape to form a disk molding die.

Specifically, the etching is a chemical etching using BCl ₃ reactive gas plasma ions. The pressure ratio between Ar and BCl ₃ is 1: 5, gas pressure 2 × 1
The test was performed under the conditions of 0 ^-4 Torr, an ion beam incidence angle of 75 °, an acceleration voltage of 100 mA / 300 V, and a magnet current of 2 A.

A disk substrate was manufactured by injection-molding plastic using the disk-molding die thus manufactured.

Then, a magnetic recording layer was formed on the disk substrate manufactured as described above by a sputtering method using Ar as a sputtering gas. Here, the magnetic recording layer includes an underlayer serving as an underlayer of the magnetic layer, a magnetic layer including a 0.5 mm-thick intermediate layer made of Cr in the middle, and a protective layer for protecting the magnetic layer. , In this order. Then, a lubricant layer was further formed on such a magnetic recording layer to obtain a magnetic disk.

Specifically, the underlayer was formed by forming a 10 nm Cr film at a sputter gas pressure of 0.1 Pa and a film formation rate of 2 nm / sec. The magnetic layer was formed by depositing Co ₆₄ Pt ₂₀ Cr ₁₆ to a thickness of 24 nm at a sputtering gas pressure of 0.1 Pa and a deposition rate of 2 nm / sec.
Further, the protective layer was formed by forming a film of C to a thickness of 13 nm at a sputtering gas pressure of 0.5 Pa and a film formation rate of 0.5 nm / sec. Further, the lubricant layer is made of FomblinZ-Do.
1 was formed by a dipping method so that the film thickness became about 2 nm.

When the magnetic characteristics of the magnetic recording layer of the magnetic disk manufactured as described above were measured using a vibrating sample magnetometer (VSM), the residual magnetization thickness Mr · t = 9 mA was obtained. The magnetic force Hc was 167 kA / m, and the coercive force squareness ratio S ^* was 0.8.

In the magnetic disk of the fourth embodiment, the step t ₁₀₀ between the groove 102 and the land 101 is 200 nm, the width t ₁₀₁ of the upper surface of the land ₁₀₁ is 3.77 μm, and the land 1
01 and the width t of the slope 103 at the boundary between the grooves 102
₁₀₃ is 0.03 μm, and the width t ₁₀₂ of the bottom surface of the groove ₁₀₂ is 0.97 μm. At this time, the width Lw of the land 101
= T ₁₀₁ + t ₁₀₃ is 3.80 μm, and the groove 102
Width Gw = t ₁₀₂ + t ₁₀₃ of a 1.00 .mu.m, these ratios Lw / Gw is 3.80.

Numerical values indicating the shapes of the groove 102 and the land 101 are obtained by using an atomic force microscope (AFM).
02 and the shape of the land 101 are actually measured.

Comparative Example 2 First, an Ir film was formed on a substrate by a sputtering method using Ar as a sputtering gas.

Specifically, the degree of vacuum was 5 × 10 ⁻⁵ Pa, the sputtering gas pressure was 0.2 Pa, the input power was 800 W, and the film formation rate was 1
The test was performed under the condition of 0 μm / 3000 s.

Next, a photoresist was applied to the above-mentioned Ir film which was polished and mirror-finished.

The photoresist was exposed and developed in accordance with a predetermined pattern, thereby forming a resist pattern in which only pits and grooves were left in accordance with the predetermined pattern.

Using the remaining photoresist as a mask, the Ir film was etched. A portion of the Ir film corresponding to the pit and groove equivalent portions of the photoresist was formed in a convex shape to form a disk molding die.

Specifically, the etching is a physical etching in which a groove is dug by hitting ions, and an Ar pressure of 2 × 1
The test was performed under the conditions of 0 ^-4 Torr, an ion beam incidence angle of 75 °, an acceleration voltage of 100 mA / 300 V, and a magnet current of 2 A.

A disk substrate was manufactured by injection-molding plastic using the disk molding die manufactured as described above.

Then, a magnetic recording layer was formed on the disk substrate manufactured as described above in the same manner as in the example, and a lubricant layer was further formed on the magnetic recording layer to obtain a magnetic disk.

In the magnetic disk of Comparative Example 2, the step t ₁₀₀ between the groove 102 and the land 101 is 200 nm, the width t ₁₀₁ of the upper surface of the land ₁₀₁ is 3.38 μm, and the land 1
01 and the width t of the slope 103 at the boundary between the grooves 102
₁₀₃ is 0.56 μm, and the width t ₁₀₂ of the bottom surface of the groove ₁₀₂ is 0.30 μm. At this time, the width Lw of the land 101
= T ₁₀₁ + t ₁₀₃ is 3.94 μm, and the groove 102
The width Gw = t ₁₀₂ + t ₁₀₃ is 0.86 μm, and their ratio Lw / Gw is 4.58.

Evaluation of Off-Track Characteristics Recording and reproduction were actually performed on the magnetic disks manufactured as described above, and their off-track characteristics were measured.

Here, a composite magnetic head combining an inductive magnetic head functioning as a recording magnetic head and a magnetoresistive magnetic head functioning as a reproducing magnetic head was used for recording and reproduction. A recording magnetic head composed of an inductive magnetic head has a track width of 4.4 μm and an interval of a magnetic gap of 0.5 μm, and a reproducing magnetic head composed of a magnetoresistive magnetic head is used. , Track width 3.6μ
m, the distance between the magnetic shields sandwiching the magnetoresistive element was 0.36 μm.

The above-mentioned composite magnetic head was used by incorporating it into a so-called 50% nano slider in order to secure a contact with the magnetic disk. Here, the slider length was 2.0 mm and the slider width was 1.6 mm. Recording and reproduction were performed by rotating the magnetic disk at a linear velocity of 7.36 m / sec. At this time, the flying height of the composite magnetic head is about 60 nm.

The measurement of the off-track characteristic is shown in FIG.
As shown in FIG. 3, data D101, D102, D103, D104, D
After writing 105, the reproduction was performed by reproducing the data D103 with the reproducing magnetic head 104.

[0098] That is, first, a target for measurement of off-track characteristics tracks from (hereinafter, referred to as recording tracks.), As shown in t _111, t ₁₁₂ in FIG. 9, left and right shifted 1.92μm respectively 2 Temporary data D101 and D102 were written on one track by using a recording magnetic head.

Next, data D103 to be detected was written on the recording track by using a recording magnetic head.
At this time, the width t _{113 of} the portion written on the recording track
Is equivalent to the track width T of the recording magnetic head, and is 4.4.
μm. The data D1 recorded on the recording track
03 has a data length of 8528 Bytes.

Next, the recording magnetic head was shifted from the center of the recording track by a width corresponding to 95% of the track pitch Tp, and data D104 and D105 were overwritten on two adjacent left and right tracks. That is, as shown in t _114, t ₁₁₅ in FIG. 9, the right and left two tracks separated by 4.56μm from the center of the recording track, is overwritten with data D104, D 105 using a recording magnetic head.

Then, reproduction is repeatedly performed on the area in which data has been written as described above while the reproducing magnetic head 104 having the track width t ₁₁₆ of 3.6 μm is slightly shifted from the center of the recording track. The bit error rate was measured by comparing the obtained data with the original recording data. Here, the standard of the bit error rate is 10
^-7 . That is, the maximum off-track amount that satisfies the bit error rate of 10 ⁻⁷ was used as the evaluation criterion.

The results of measuring the off-track amount of the magnetic disk of Example 4 and the magnetic disk of Comparative Example 2 are shown in FIGS. 10 and 11, respectively.

FIG. 12 shows the width t of the upper surface of the land 101.
₁₀ is a theoretical curve of the maximum off-track amount for ₁₀₁ . Solid line A and solid line B represent Example 4 and Comparative Example 2, respectively.
7 is a theoretical curve for a magnetic disk manufactured using the disk molding die of FIG. A solid line C is a theoretical curve for a magnetic disk having a flat surface.

[0104] The magnetic disk of Comparative Example 2, the width t ₁₀₁ of the land top is 3.38Myuemu, maximum off-track amount was 1.34 .mu.m. This result is almost in agreement with the theoretical curve in FIG. 12, the maximum off-track amount of the magnetic disk of Comparative Example 2 was considerably smaller than that of the magnetic disk having a flat surface, and the off-track characteristics were deteriorated.

[0105] On the other hand, the magnetic disk of Example 4, the width t ₁₀₁ of the land top is 3.77Myuemu, maximum off-track amount was 1.59. This result is almost in agreement with the theoretical curve in FIG. 12, the maximum off-track amount of the magnetic disk of Example 4 was larger than that of the magnetic disk having a flat surface, and excellent off-track characteristics were obtained.

The results of Comparative Example 2 and Example 4 are shown in FIG.
Of which substantially coincides with the theoretical curve, the width t ₁₀₁ of the land upper surface
It is presumed that even if the experiment is carried out in the same manner as above, a result similar to the theoretical curve can be obtained.

As is clear from FIG. 12, a magnetic disk manufactured by using a disk molding die formed by forming a Ti film and by reactive ion etching is superior to a magnetic disk having a flat surface. It was found to have off-track characteristics.

[0108]

As is apparent from the above description, according to the present invention, as a magnetic recording medium having a groove formed along a recording track, the fluctuation of the flying height of the magnetic head during recording / reproducing can be reduced. It is possible to provide a magnetic recording medium having excellent track characteristics, and a magnetic recording / reproducing apparatus capable of satisfactorily performing recording / reproducing on such a magnetic recording medium. Further, according to the present invention, the off-track characteristics can be improved, so that it is possible to further increase the track density. Further, according to the present invention, it is possible to provide a magnetic disk on which pits and grooves have been formed in advance, better off-track characteristics than when the disk surface is flat.

[Brief description of the drawings]

FIG. 1 is a plan view schematically showing the state of irregularities in a data zone and a servo zone in an example of a magnetic disk to which the present invention is applied.

FIG. 2 is a cross-sectional view schematically showing the appearance of irregularities in a data zone and a servo zone along line AA in FIG.

FIG. 3 is a diagram schematically showing a recording pattern when measuring a bit error rate.

FIG. 4 is a diagram showing a measurement result of a relationship between an off-track amount of a reproducing magnetic head and a bit error rate.

FIG. 5 is a diagram showing a relationship between a width t _{1 of a} land upper surface and a maximum off-track amount.

FIG. 6 is a diagram showing a relationship between a recording magnetic head having a track width T that is too large, and lands and grooves.

FIG. 7 is a diagram showing a relationship between a recording magnetic head having a track width T of (t ₁ + Tp / 5), lands, and grooves.

FIG. 8 is a cross-sectional view schematically showing an uneven state of a data zone and a servo zone in an example of a magnetic disk to which the present invention is applied.

FIG. 9 is a diagram schematically showing a recording pattern when measuring a bit error rate.

FIG. 10 is a diagram showing a measurement result of a relationship between an off-track amount of a reproducing magnetic head and a bit error rate.

FIG. 11 is a diagram showing a measurement result of a relationship between an off-track amount of a reproducing magnetic head and a bit error rate.

And [12] width t ₁₀₁ of the land top is a diagram showing a relationship between the maximum amount of off-track.

[Explanation of symbols]

1 pit, 2 servo zone, 3 groove,
4 data zone, 10 reproducing magnetic head, 11
Recording magnetic head, Lw land width, Gw groove width, t ₁ , t ₁₀₁ Land upper surface width, t ₂ , t ₁₀₂
Groove bottom width, t ₃ , t ₁₀₃ Width of slope at boundary between land and groove

Claims (8)

[Claims] 1. In a magnetic recording medium in which unevenness corresponding to a servo signal is formed and a groove is formed along a recording track, a width Lw of a land which is a convex portion between the grooves.
And a ratio Lw / Gw of the groove width Gw to the groove width Gw is 2.0 or more. 2. When a track pitch is Tp and a width of a slope portion at a boundary between the land and the groove is t, Lw / Gw ≦ (4/5 × Tp + t) / (1/5 × Tp−
2. The magnetic recording medium according to claim 1, wherein t). 3. The magnetic recording medium according to claim 1, wherein the ratio Lw / Gw is 7.26 or less. 4. A step between the groove and the land is 10
2. The magnetic recording medium according to claim 1, wherein the thickness is 0 nm or more. 5. An angle formed between the land and the slope at a boundary between the land and the groove and the land is 90 ° or more.
2. The magnetic recording medium according to claim 1, wherein the angle is 105 [deg.] Or less. 6. A recording magnetic head for performing magnetic recording on a magnetic recording medium in which a groove is formed along a recording track, wherein a track width T of the recording magnetic head has a protrusion between the grooves. A magnetic recording / reproducing apparatus characterized in that the width is not less than the width Lw of the land, which is a portion, and is not more than the sum of the track pitch Tp and the width Gw of the groove. 7. When the width of the land is Lw, the width of the groove is Gw, the track pitch is Tp, and the servo error margin during magnetic recording is Em, the track width T of the recording magnetic head is Lw + Em. 7. The magnetic recording / reproducing apparatus according to claim 6, wherein x2 ≦ T ≦ Tp + Gw−Em × 2. 8. A metal film forming step of forming a metal film by applying a metal material on a substrate when producing a disk molding die comprising a substrate and a metal film formed on the substrate. And applying a photoresist on the metal film formed in the metal film forming step, exposing and developing the photoresist according to a predetermined pattern, thereby leaving only a pit and / or groove equivalent portion. A cutting step of forming a pattern; and a reactive ion etching of the metal film using the photoresist left in the cutting step as a mask, of the metal film corresponding to the pits and / or grooves of the photoresist. An etching step of forming a portion corresponding to and in a convex shape to form a disk molding die; and a disk molding die. Manufacturing method.