JPH08147916A - Recording / playback method - Google Patents

Abstract

(57) [Summary] [Structure] In a recording / reproducing method of reading / writing data from / to a magnetic disk by a magnetic head by a contact start-and-stop (CSS) method, as a magnetic disk, a protrusion is formed in a CSS area where the magnetic head performs CSS. Using a magnetic disk having the projections and the height of the projections gradually decreasing toward the data recording area, there is a projection having a height lower than the average projection height.
In the CSS region where no protrusion exists near the S region or the protrusion existing region, the magnetic head is lowered to the magnetic disk and levitated from the magnetic disk, and in the CSS region where a protrusion having a height higher than the average protrusion height exists, the magnetic head Recording and playback method to make the still. [Effect] It is possible to develop a high-density magnetic recording device that does not cause sticking.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording / reproducing method,
Specifically, it relates to a recording / reproducing method performed by a contact start and stop (CSS) method in a magnetic disk device using a magnetic disk such as a hard disk.
In particular, the present invention relates to a recording / reproducing method capable of simultaneously achieving sticking characteristics of a magnetic head on the surface of a magnetic disk and lowering the flying height of the magnetic head while maintaining good CSS characteristics.

[0002]

2. Description of the Related Art Usually, writing / reading of information to / from a hard disk is performed via a magnetic head, and at that time, the hard disk rotates at high speed to levitate the magnetic head. In order to improve the magnetic characteristics, a hard disk is mechanically formed on the substrate surface of the disk or on a base layer made of a non-magnetic material such as NiP plating provided on the substrate surface in a concentric circular shape in the circumferential direction of the magnetic disk. Processing (hereinafter, referred to as mechanical texture) is performed by polishing to leave processing marks.

Due to the recent increase in the amount of information and the demand for smaller and lighter devices, the linear recording density and track density have increased,
As the area per pit becomes smaller, scratches due to mechanical texture as in the conventional case have a higher probability of becoming an error at the time of reading information. Therefore, a method has been proposed in which only the CSS area on the inner circumference of the magnetic disk is mechanically textured and the data recording area is left as it is. However, in this case, the surface of the data recording area is CSS.
The height of the surface of the region is higher than that of the region, and it is difficult to make the step have a smooth slope, and there is a problem that the magnetic head crashes when seeking.

Also, a method of making a texture pattern by a laser has been proposed in place of such a mechanical texture. Examples of the texture by a laser are disclosed in US Pat. Nos. 5,062,021, 5,108,781 and the like, and the NiP layer is locally melted by a strong pulsed laser beam of Nd-YAG. As shown in FIG. 2, the concave hole 6 formed by melting and the rim portion 7 having a diameter of 2.5 to 100 μm formed by the molten NiP around the hole 6 rising and solidifying due to surface tension. An attempt has been made to improve the CSS characteristics with the magnetic head by forming a large number of crater-shaped concavities and convexities made of a torus and using an annular convex rim.

When this method is used, the CSS of the magnetic head is
It is possible to texture only the area. However, even in this case, in order to prevent sticking of the magnetic head, the protrusion height of the CSS region needs to be above a certain level, and the glide height increases by the height of the protrusion. Therefore, since the glide height of the magnetic disk is regulated by the glide height of the CSS area, the head flying height becomes excessive in the data recording area, and the recording density cannot be increased sufficiently. there were.

[0006]

Therefore, in the magnetic disk recording / reproducing method, the stable flying height of the magnetic head in the data recording area can be made sufficiently low to the extent specified by the glide of the data recording area. Further, it is desired that the magnetic head can be stopped on a protrusion having an appropriate height such that sticking does not occur in the CSS area.

[0007]

The present invention has been made for the purpose of fully exploiting the performance of such a high-density magnetic recording disk. The gist of the present invention is to contact the read / write of data with respect to a magnetic disk by a magnetic head. In a recording / reproducing method performed by a start-and-stop (CSS) method, a magnetic disk has a protrusion in a CSS area where CSS is performed, and the height of the protrusion gradually decreases toward a data recording area. The magnetic head is used to descend to and fly from the magnetic disk in the CSS area where there are projections with a height lower than the average projection height or in the CSS area where there is no projection near the projection existing area. In a CSS area where protrusions with a height higher than the average protrusion height exist, the magnetic head is Recording and reproducing method for causing a consists in.

The present invention will be described in detail below. According to the present invention, a magnetic disk is used in which a protrusion is provided in the CSS area on the disk surface so that the height of the CSS gradually decreases toward the data recording area. The part where the head has a height lower than the average height of the protrusions (the height of the protrusions is low) where the head is lowered to the magnetic disk and floats from it.
Alternatively, the projection is not provided and is mechanically textured in the vicinity of the projection forming part, the magnetic head is moved along with the low speed rotation of the magnetic disk, and the final rest position of the magnetic head is It is a CSS region (a portion having a high protrusion height) in which protrusions having a height higher than the average protrusion height of the protrusions are present. In this case, the movement of the magnetic head to a portion having a high protrusion height may be performed immediately after the magnetic disk is stopped as long as it is before the magnetic head causes sticking.

As a preferred method for producing the magnetic disk used in the present invention, a magnetic disk substrate having a nonmagnetic underlayer made of a nonmagnetic material such as NiP on a nonmagnetic substrate is rotated while the surface is circular. Examples include a method of forming projections on the surface by irradiating an energy beam or the like whose output is accurately controlled along the circumferential direction. Examples of energy beams include pulsed lasers, electron beams, and X-rays.
Above all, it is preferable to use a pulse laser, and the present invention will be described below by taking the case of using a pulse laser as an example.
Further, the above-described underlayer may not be formed on the magnetic disk substrate, and the pulse laser may be scanned on the substrate instead of rotating the substrate. Then to this,
After providing an intermediate layer as needed, a magnetic layer is provided, and then a protective layer is usually formed to produce a magnetic disk used in the present invention.

In the present invention, the mechanism of protrusion formation is not yet fully understood, but it is considered as follows. FIG. 1 is a conceptual diagram showing an expected generation mechanism of protrusions. FIG.
In (a), the locally overheated spot portion 5 of the underlayer 4 irradiated with the pulse laser 3 is partially melted, and the melted portion is caused by rotation of the substrate (direction is indicated by an arrow) or laser beam scanning. Moves. As shown in FIG. 1 (b), the temperature of the portion where the beam first hits then decreases and a temperature gradient occurs. Generally, in a molten liquid, the surface tension is higher on the low temperature side, and due to this difference in surface tension, the part that was first irradiated by the beam and melted and then became low temperature takes up the liquid of the melted part later and rises up. . Therefore, as shown in FIG. 1C, a concave portion is formed in the last melted portion, and the concave portion is provided at the rear portion of the protrusion with respect to the scanning direction of the laser beam. That is, the vertical cross-sectional shape that passes through the center of the protrusion and includes the scanning direction of the laser beam has a concave portion on one side of the bottom portion of the protrusion.

In the present invention, the scanning direction of the laser beam is not limited to the scanning direction of the laser beam on a stationary disk, but the laser beam is stationary and the disk is irradiated in a rotated state. It also indicates the direction of rotation of. Depending on conditions such as slow scanning of the laser beam or rotation of the substrate, or high power of the laser beam, thermal contraction may cause depressions around the bottom of the protrusion. Although this phenomenon is not fully understood, the locally heated spot expands,
Since the surrounding area is cold and difficult to deform, the expanded part is immediately cooled by the outside air and remains as a protrusion. Around the protrusion, a recess is formed due to heat shrinkage.

The height of the protrusions can be freely controlled by adjusting the intensity of the laser, the average irradiation time thereof, and the linear velocity of the disk, and the density of the protrusions can be determined by the number of protrusions per revolution and the radius of the pulse laser. The irradiation interval in the direction and the condition for controlling the height of the protrusions are adjusted to freely control. Usually the laser intensity is 20-500 mW,
Average irradiation time is 0.05 to 100 μsec, laser spot diameter is 0.2 to 4 μm, and substrate linear velocity is 0.8 to 1
5 m / sec is preferable. Here, the average irradiation time of the laser refers to the time during which the surface of the underlayer is irradiated with the laser to form one protrusion.

To change the irradiation area of the laser beam, it is usually necessary to change the aperture ratio of the objective lens.
By using the objective lens of 1 to 0.95, the irradiation diameter of the beam can be controlled to about 0.7 to 6 μm. Magnetic disks used in the present invention, the maximum protrusion height of the protrusion existing in CSS region 200nm or less, the protrusion density is 10 ^2-1
0 ⁶ / mm ^2, it is preferable slope of the disk radial projection height extending from the inner circumferential portion disk to the outer peripheral portion is 0.0001 or less. Projection density may become underpin the head lower surface only projection is difficult due to the influence of such undulation of the substrate is less than 10 ² / mm ^2, also ¹⁰⁶ / m
If it is attempted to form protrusions exceeding m ² , it may be difficult to make the protrusions uniform in height due to laser interference or the like. As for the shape of the protrusion in the present invention, it is preferable that the average value of the area of the figure surrounded by contour lines at a height 1 nm below the apex of each protrusion is 2 μm ² or less,
More preferably, it is 0.001 to 0.5 μm ² . The average value of the area of the figure surrounded by the contour lines is a surface profile measuring device by laser interference, for example, "ZY" manufactured by Zygo, Inc. in the United States.
It can be measured by GO ".

In the present invention, the height of the protrusion means the height of the protrusion with respect to the center line of the roughness curve defined by JIS surface roughness (B0601). The density of protrusions is not the average density of the entire magnetic disk, but the density per unit area of the protrusions. In the present invention, a silicon substrate, an aluminum alloy plate or a glass substrate is usually used as the non-magnetic substrate, but a metal substrate of copper, titanium or the like, a ceramic substrate, a resin substrate or the like can also be used.

It is desirable that the material of the substrate has a small surface reflectance and a small thermal diffusivity in view of the relationship between heat generation by laser irradiation and heat dissipation by heat conduction. The underlayer is usually made of a nonmagnetic material, preferably a NiP alloy layer, and is usually formed by an electroless plating method or a sputtering method. The thickness is preferably 50 to 20,0.
00 nm, particularly preferably 100 to 15,000 nm.

An intermediate layer such as a Cr layer or a Cu layer is preferably provided between the magnetic layer and the underlayer, and the thickness thereof is usually 20 to 200 nm, preferably 50 to 10 nm.
It is 0 nm. The magnetic layer provided on the underlayer or the intermediate layer is formed by a method such as electroless plating, electroplating, sputtering or vapor deposition, and is made of Co-P, Co-Ni-P, Co.
-Ni-Cr, Co-Ni-Pt, Co-Cr-Ta,
A ferromagnetic alloy thin film such as a Co—Cr—Pt or Co—Cr—Ta—Pt alloy is formed, and the film thickness is usually 30 to 70.
It is about nm.

A protective layer is provided on the magnetic layer,
As the protective layer, a carbon film, a hydrogenated carbon film, a carbide film such as TiC and SiC, Si, or the like is formed by a method such as vapor deposition, sputtering, plasma CVD, ion plating, or a wet method.
A nitride film of N, TiN or the like, an oxide film of SiO, AlO, ZrO or the like is formed. Of these, a carbon film and a hydrogenated carbon film are particularly preferable. A lubricant layer is usually provided on the protective layer.

In the magnetic disk used in the present invention, the protrusion exists only in the area where the magnetic head performs CSS and does not exist in the data recording area, and the height of the protrusion decreases toward the data recording area. There is. When the magnetic recording device is stopped, the magnetic head is placed in the portion of the CSS area where the sticking is small and the protrusion height is high. When the drive is started, the magnetic head moves to a portion having a low protrusion height in the CSS area as the disk rotates. This part sticks when the magnetic head stops on the magnetic disk, but the frictional force in the sliding state is designed to be sufficiently small. When the number of rotations of the magnetic disk reaches the specified high-speed rotation, the magnetic head is completely separated from the magnetic disk and can move freely in the data recording area.

When the magnetic recording apparatus is driven, when the magnetic head is not sought on the data recording area, the magnetic head is located in the area with a low protrusion height in the CSS area in case of emergency such as power failure. It is desirable to wait. Therefore, it is desired that the CSS area having a low protrusion height has a glide height almost equal to that of the data recording area.

When the driving magnetic recording apparatus is stopped, first, the magnetic head moves from the data recording area to an area having a low protrusion height in the CSS area. After this, the number of revolutions of the magnetic disk is reduced to lower the flying height of the magnetic head,
When the bottom of the magnetic head comes into contact with the protrusion, it is desirable to move and stop the magnetic head in the CSS region where the protrusion height is high.

Further, in the case where the entire surface of the magnetic disk is provided with a mechanical texture having a small surface roughness that causes no sticking when the magnetic head is stationary, the vicinity of the CSS area is provided. The magnetic head may be grounded on the surface of the mechanical texture. In addition, when the CSS region is textured with a laser, it is preferable to use a substrate whose entire surface is mechanically textured with a low glide in advance. In this case, compared to the case of using a simply polished substrate, sticking is less likely to occur even when the protrusion density and protrusion height made by laser are lowered, that is, even in the situation where the substrate and the magnetic head partially contact, In addition, the coefficient of friction is also reduced. Also,
In this case, since the conditions for producing the laser texture are widened, it is a preferable method especially for mass production.

[0022]

EXAMPLES Next, the present invention will be described more specifically by way of examples, but the present invention is not limited to the following examples unless it exceeds the gist. Example 1, Comparative Examples 1 to 3 An aluminum substrate coated with a NiP underlayer having a diameter of 90 mm was mechanically textured so as to have a surface roughness Ra of 2 nm or less, and used as a non-magnetic substrate.

Next, the strengths shown in Table 1 (in Example 1, as the radius decreased, 165 mW to 260 m
Changed to W. ) Was precisely irradiated to the CSS pulse region of the non-magnetic substrate under the conditions shown in Table 1 to form protrusions. Then, a Cr intermediate layer (10
0 nm), a Co-Cr-Ta alloy magnetic film (50 nm) and a carbon protective film (20 nm) are formed, and then a fluorine-based liquid lubricant ("DOL-2000" manufactured by Monte Edison Co., Ltd.) is applied to a thickness of 2 nm by an immersion method. Then, a magnetic disk was produced. An aluminum substrate coated with a NiP underlayer having a diameter of 90 mm was mechanically textured so that the surface roughness Ra was 2 nm or less, and in Comparative Example 3, an aluminum substrate coated with a NiP underlayer having a diameter of 90 mm was used. A magnetic disk manufactured by the same process as in Example 1 was used, except that a substrate having a texture of Ra of about 2 nm (not laser-textured) by a conventional mechanical texture method was used. I was there.

In Table 1, in Example 1 and Comparative Examples 1 to 3, conditions when the protrusions were formed on the non-magnetic substrate (the linear velocity of the rotated substrate, the intensity of the irradiated laser, the average irradiation time of the laser, The numerical aperture NA of the objective lens used for focusing the laser is shown. The spot diameter at which 84% of the energy is concentrated is represented by 1.22 × λ / NA. Also, the average protrusion density of the formed protrusions, the average protrusion height, 1 from the protrusion tip.
Table 1 shows the cross-sectional area of the part lower by nm. In addition, the cross-sectional area shown in Table 1 represents the cross-sectional area at a portion 1 nm lower than the tip of the protrusion.

[0025]

[Table 1] Table-1 ------------------------------------- Substrate Laser Average Average Average Average Projection Projection Objective lens Linear velocity Strength Radiation time Density Elevation Cross section Area aperture (mm / sec) (mW) (μsec) (pieces / mm ² ) (nm) (μm ² ) [NA] −−−− −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− Example 1 1714 165 to 260 1.25 9260 5 to 56 0.38 to 0.08 0.6 Comparative example 1 1714 165 1.25 9260 5 0.38 0.6 COMPARATIVE EXAMPLE 2 1714 300 1.25 9260 56 0.08 0.3 COMPARATIVE EXAMPLE 3 MECHANICAL TEXTURE ------------------------------- −−−−−−−−−−

Table 2 shows the CSS data of each obtained disk.
Static friction coefficient before strike (initial stiction) and CS
The frictional force after S20,000 times was shown. CSS test is a magnetic head
Thin film with floating height of 1.6μ inch and loadgram of 6gf
Head (Slider material: Al ₂O₃TiC) was used. Well
In addition, the flying height of the magnetic head is
Gravity stability of the magnetic head during seek between SS areas
Evaluation was performed using an id tester. Stable ascent of CSS area
The height of the comparative example 1 is 1.1 μ inch, and the height of the comparative example 2 is about 2.
Comparative Example 3 having a size of 4 μm and only mechanical texture
Was 1.0 μ inch. From this, the example
The glide height of 1 is 1.1 to 2.4 μm in the CSS area.
It seems that it is changing continuously between the branches. Implementation
In Example 1, the CSS area has a radius of 19 to 21 mm.
As a result, the height of the protrusion gradually decreases in the outer peripheral direction. Magnetic
The stop position of the head is a position with a radius of 20 to 21 mm,
When the magnetic disk rotates, the magnetic head gradually moves outward.
To the stable disk rotation speed (5,400 rp
By the time it reaches m), the magnetic head has a radius of 19 to 20 m.
Move to the m position and ascend.

On the contrary, when the magnetic head is stopped, the radius of the magnetic head is 2
The rotation speed of the magnetic disk is reduced until the magnetic head and the protrusion of the magnetic disk come into contact with each other at a position of 0 to 21 mm, and then a radius of 20 to 21 before the magnetic disk stops.
The magnetic head is moved to the mm part. Therefore, the stickion of Example 1 and the frictional force after 20,000 times are values at the position of the radius of 20 to 21 mm.

[0028]

[Table 2] Table-2 ---------------------------------------- Initial stiction CSS after 20,000 times (friction coefficient) Friction force ----------------------------------- Example 1 0.12 3 gf Comparative Example 1 4.41 36 gf Comparative Example 2 0.12 Head Crash Comparative example 3 5.19 Stop adsorption drive (750 times) -------------------------

As is apparent from Table-2, the one having only the mechanical texture (Comparative Example 3), and the one having the protrusions with an average protrusion height of 5 nm added thereto by the laser (Comparative Example 1)
, Sticktion, the value of friction force is insufficient. In addition, the one with the protrusions having an average protrusion height of 56 nm by the laser (Comparative Example 2) has a better stickion,
A low-flying magnetic head hits a protrusion and causes a head crash.

On the other hand, the magnetic disk of the present invention in which the protrusion height is continuously changed in the CSS area (Example 1)
Shows that sticking is low and head crash does not occur.

[0031]

According to the present invention, the stable flying height of the magnetic head in the data recording area can be made sufficiently low to the extent specified by the glide of the data recording area, and sticking does not occur in the CSS area. Since the magnetic head can be stopped on a protrusion having an appropriate height that does not exist, it is possible to develop a high-density magnetic recording device without sticking, which is very useful industrially.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing an expected generation mechanism of protrusions of the present invention.

FIG. 2 is a perspective view showing a shape of a medium surface according to a conventional method.

[Explanation of Codes] 3 pulse laser 4 underlayer 5 spot portion 6 concave hole portion 7 rim portion

Front page continuation (72) Inventor Yoji Arita 1000 Kamoshida-cho, Aoba-ku, Yokohama-shi, Kanagawa Mitsubishi Chemical Corporation Yokohama Research Institute

Claims (3)

[Claims] 1. A recording / reproducing method for reading / writing data from / to a magnetic disk by a magnetic head by a contact start and stop (CSS) method, wherein the magnetic head performs CSS as a magnetic disk.
Using a magnetic disk having protrusions in the region and the height of the protrusions gradually decreasing toward the data recording region, a CSS region or protrusion existing region in which protrusions having a height lower than the average protrusion height exist In the CSS area where no protrusion is present in the vicinity, the magnetic head is lowered to the magnetic disk and levitated from the magnetic disk, and the magnetic head is made to stand still in the CSS area in which a protrusion having a height higher than the average protrusion height exists. Recording and playback method. 2. The maximum protrusion height of the protrusion is 200 nm or less,
The protrusion density is 10 to 10 ⁶ / mm ² , and the gradient of the protrusion height in the radial direction from the disk inner peripheral portion to the outer peripheral portion is 0.0.
The recording / reproducing method according to claim 1, wherein the recording / reproducing method is 001 or less. 3. The recording / reproducing method according to claim 1, wherein the average value of the area of a figure surrounded by contour lines at a height 1 nm below the apex of each protrusion is 2 μm ² or less.