JPH05189736A - Magnetic disk substrate and magnetic disk formed by using the same and production thereof - Google Patents

Abstract

PURPOSE:To satisfy the low coefft. of friction of a disk surface with a head and the durability to attraction by forming a rough surface consisting of fine dotty ruggedness on the surface of the magnetic disk substrate to the surface roughness of a specific characteristic value. CONSTITUTION:The rough surface 16 consisting of the fine dotty ruggedness is formed on the surface of the magnetic disk substrate 11. The state of such rough surface 16 is formed to the surface roughness of 60 to 240Angstrom center line average roughness Ra, 500 to 2000Angstrom max. roughness Rtm, 300 to 1500Angstrom height Rpm of a center line peak and 0.5 to 0.75 value of Rpm/Rtm. Such state is obtd. by bringing the extremely fine abrasive grains suspended in fluid into collision against the surface of the substrate 11, thereby roughening the surface. The lower floating and lower coefft. of friction of the magnetic head and the surface characteristic having the good durability to attraction are obtd. The lower floating at <=0.1mum of the magnetic head on the disk surface is enabled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk suitable for application to a hard disk, a magnetic disk substrate used for the same, and a method for manufacturing the same. Be able to cope with the emergence.

[0002]

2. Description of the Related Art Horizontal magnetic recording media are broadly classified into coating type magnetic recording media and plating type and sputter type magnetic recording media depending on the structure of the medium. The plating-type and sputter-type magnetic recording media have the advantage of higher recording density than the coating-type magnetic recording media. As shown in FIG. 8, this type of plating or sputter type medium comprises a Ni-P plating base layer 2, a Co-Ni-P layer, and a Co-Ni layer formed on a substrate 1 made of Al in this order from the bottom. A magnetic film 3 made of a plated or sputtered film, a protective film 4, and a lubricating film 5 are laminated.

In this case, the surface of the magnetic disk substrate 1 is
In order to secure a low coefficient of friction and good adsorption durability in relation to the magnetic head, so-called texture processing is performed in which a large number of fine streaky grooves are provided along the circumferential direction to roughen the surface. Be seen. Originally, the texture processing is intended to cause magnetic anisotropy in the circumferential direction of the disk during the sputtering processing, but in order to prevent head adsorption, the roughness of the substrate surface is further increased than the original purpose. The reality is that it must be increased. Of course, the adsorption durability is influenced not only by the roughness due to the texture but also by the characteristics of the protective film and lubricating film on the magnetic disk surface. The larger the size, the better the adsorption durability in general.

Therefore, the magnetic disk substrate 1 is textured so as to give a certain degree of roughness in consideration of the friction coefficient and the adsorption durability.

Generally, the roughness of the substrate 1 in the radial direction by the texture has an average roughness (Ra) of 50 to 100Å, a maximum roughness (Rtm) of 450 to 600Å, and a center line mountain height or center line C (in FIG. 9). The height (Rpm) of the mountain from the center of the cross-sectional area of the mountain shown is 150 to 250Å, and Rpm / Rt
The ratio of m is 0.3 to 0.4.

However, in view of the nature of the texture processing, if the roughness is increased, surface defects such as scratches or minute protrusions are likely to occur, and these defects will cause an accident such as head crash later.

[0007]

On the other hand, in order to improve the recording density of the magnetic disk, there is a so-called low flying height, in which the flying distance between the magnetic disk surface and the magnetic head which opposes the magnetic disk surface is reduced. Is needed. But,
In a magnetic disk using a conventional texture substrate, that is, a substrate provided with a certain degree of roughness, the S / N ratio is lowered due to the surface shape anisotropy, and scratches and minute protrusions caused by the above-described texture processing are generated. However, there is a drawback in that the surface defect portion and the head come into contact with each other, which may cause traveling failure or damage to the magnetic disk surface.

On the other hand, a magnetic disk in which the surface roughness of the magnetic disk substrate due to the texture is reduced has a large friction coefficient, and, for example, the contact of the magnetic head with the magnetic disk in a floating magnetic head, that is, the start of driving of the disk. Contact before and after, so-called CSS
The friction coefficient increases more and more due to repeated (contact start stop), and the contact between the magnetic disk surface and the magnetic head while the disk drive is stopped in a stopped state causes adsorption, which makes restarting difficult, and finally In some cases, it may not be able to fulfill its role.

The present invention has been made under such circumstances, and its problems are to reduce the flying height of a magnetic head, to reduce the friction coefficient, and to improve the recording density of a magnetic disk. (EN) It is possible to provide a magnetic disk substrate that enables good adsorption durability, a magnetic disk using the same, and a method for manufacturing a magnetic disk substrate.

[0010]

[Means for Solving the Problems] In order to solve such a problem, as a result of earnest research, as a result of making ultrafine abrasive grains suspended in a fluid collide with the substrate surface to roughen the surface, the magnetic head has a low flying height. It has been found that the optimum surface properties can be obtained for a low friction coefficient and good adsorption durability, and the present invention can be provided.

That is, according to the present invention, as shown in the schematic cross-sectional view of FIG. 1, a rough surface is formed on the surface of a magnetic disk substrate, which is formed by finely arranging dot-shaped irregularities 16 or dot-shaped concave portions. The center line average roughness (Ra) is 60 to 240Å and the maximum roughness (Rtm) is 50.
0 to 2000Å, center line mountain height (Rpm) is 300 to 1
500Å and the ratio of Rpm / Rtm is 0.5 to
Magnetic disk substrate 11 having a surface roughness of 0.75
Make up.

The surface roughness referred to in the present invention is an ultra-precision roughness meter (made by Rank Taylor Hobson Co., Ltd.) in which a stylus with a tip of 2.5 μm is run on the surface with a force of 40 μN.
Using, measurement length 0.49mm, cutoff 0.08
Ra is the centerline average roughness, Rtm is the average value of the maximum amplitude in each cutoff, and Rpm is the average value of the centerline maximum peak heights in each cutoff. ..

Still another aspect of the present invention is a magnetic disk substrate 11
Is a disc-shaped substrate 21 made of aluminum or an aluminum alloy, and an underlayer 22 made of Ni-P plating.

Still another aspect of the present invention is a magnetic disk substrate 11.
Is a disk-shaped substrate 21 made of glass or ceramics. Still another embodiment of the present invention, as shown in the schematic cross-sectional view of the example in FIG.
The magnetic film 13, the protective film 14, and the lubricating film 15 are sequentially deposited to form the magnetic disk 17.

In the manufacturing method of the present invention, the surface of the magnetic disk substrate 11 having the above-mentioned underlayer 22 or the magnetic disk substrate 1 configured without the underlayer 22.
Step of polishing the surface of No. 1, and an average particle size of 0.5 to 5.0 μ
Solid-phase and vapor-phase two-phase flow (hereinafter referred to as solid-gas two-layer flow) in which abrasive grains composed of m are suspended in a fluid is sprayed onto a polished surface by an injection nozzle to form fine dot-like irregularities on the polished surface. 16
The magnetic disk substrate 11 is manufactured through the steps of forming.

[0016]

The magnetic disk 17 using the magnetic disk substrate 11 obtained by the method of the present invention described above exhibits excellent adsorption durability.

Now, on the aluminum alloy substrate 21, Ni-
The P-plated surface was polished with artificial leather using abrasive grains having an average particle diameter of 0.8 to 2.0 μm, and the surface roughness was 10 with Ra.
When the abrasive particles having an average particle diameter of 0.5 to 5.0 μm are suspended in an inert gas on the surface of the base layer 22 having a thickness of ˜60 Å, and the solid gas two-layer flow is blown from the injection nozzle, The surface has a cross section as shown in FIG. 1 when this is schematically shown. That is, the base 21 made of an aluminum alloy plate material
Maximum roughness (Rtm) on the surface of the above Ni-P plated underlayer
An infinite number of fine dot-like irregularities 16 of 0.05 to 0.2 μm (500 to 2000 Å), that is, a fine satin pattern is formed. When this cross section is observed, the width of the peaks is narrower than the width of the valleys.

When the magnetic film 13, the protective film 14, and the lubricating film 15 are coated on the surface of the disk substrate 11 as described above, they are attached thicker to the valleys than to the peaks as shown in FIG. After all, the roughness becomes smaller than the surface of the disk substrate 11.

On the other hand, the conventional textured surface shown in FIG. 10 was polished with artificial leather using abrasive grains having an average particle diameter of 0.8 to 2.0 μm, and the surface roughness Ra was 10
Further, the base layer 22 having a thickness of about 60 Å is further covered with a soft cloth so that
The average grain size of 8 to 2.0 μm is used, or polishing is performed in the circumferential direction using a polishing tape to which the same type of abrasive grains are adhered, and the surface roughness is set to Ra of 50 to 100 Å. is there. Therefore, as shown in FIG. 10, since it has a cross section with a narrow valley bottom width, when the magnetic film 3, the protective film 4, and the lubricating film 15 are formed on this, the valley bottom is filled up as shown in FIG. The maximum roughness (Rtm) of the surface of the magnetic disk after completion becomes smaller, and the area of the mountain portion becomes relatively larger. Therefore, it is considered that the conventional magnetic disk does not have high adsorption durability.

On the other hand, the magnetic disk 17 according to the present invention, as shown in FIG. 1, is relatively large because the center line C of the roughness curve is closer to the valley bottom than the conventional one of FIG. Indicates Rpm / Rtm.

In addition, since the conventional method is a wet-type grinding process for producing a new surface on the entire surface, surface defects such as scratches and minute projections are likely to occur, strong processing cannot be performed, and the maximum roughness (Rtm) is obtained. Despite the practical limit of 600Å, the present invention is a dry surface treatment that mainly applies a compressive force, so that surface defects are less likely to occur, and even if a certain amount of heavy machining is performed, the peak height is high. It is possible to make the thickness uniform, and the practical limit of the maximum roughness (Rtm) is 2000Å.

As described above, according to the present invention, both Rpm / Rtm and Rtm can be increased, the surface roughness after processing the medium can be kept larger, and the friction coefficient can be kept low, and the adsorption durability can be improved. Has the effect of increasing

[0023]

Embodiments of a magnetic disk substrate, a magnetic disk using the same, and a method of manufacturing the same according to the present invention will be described with reference to FIGS.

The magnetic disk substrate 11, that is, the base body 21 constituting the magnetic disk substrate 11 is made of a rigid non-magnetic material, and is formed in a disk shape having a through hole in the center.

The base 21 can be made of Al or Al. In this case, a Ni-P plated layer is formed on the surface of the base 21 as the underlayer 22 of the magnetic film 13. Also,
As the base 21, glass, ceramics, etc. are known in addition to the above-mentioned Al or its alloy.
The base body 21 itself is used as the magnetic disk substrate 11 without applying a Ni-P plating base layer as described above.

The thickness of the substrate 21 is 0.35 to 1.9 mm.
Al alloy is often used, and the Ni—P underlayer 22 is plated to a thickness of 5 to 20 μm.

Then, the surface of the magnetic disk substrate 11 is polished, and abrasive particles having an average particle diameter of 0.5 to 5.0 μm, for example, fine particles of SiC or Al ₂ O ₃ are inactivated by N ₂ gas or the like. A solid-gas phase flow suspended in a fluid such as gas or air is blown to form irregularities 16 in which fine dot-shaped concave portions shown in FIG. 4 are densely dispersed on the polishing surface.

Then, on the disk substrate 11 thus roughened, Co--N is formed by plating or sputtering.
forming a metal magnetic film 13 such as i-P or Co-Ni,
A well-known protective film 14 and a lubricating film 15 are formed on this.

Example 1 Outer diameter 95 mm, inner diameter 25 mm, thickness 1.27 mm
Of the Al-Mg-based aluminum alloy ring-shaped disc body is prepared, and the Ni-P underlayer 22 is provided on both sides of the base body 21.
Is formed by electroless plating, and then 1.
Polished with an abrasive having an average particle diameter of 0 μm to obtain a surface roughness R
So-called normal polishing was carried out to obtain 20Å in a, and the thickness of the underlayer 22 was set to 15 μm. After that, fine spot-like concavities and convexities 16 were simultaneously formed on both surfaces of the substrate 11 by using a free abrasive grain jetting processing device that generates a solid-gas two-phase flow of the SiC fine powder and N ₂ gas.

This free-abrasive blasting machine is disclosed in Japanese Unexamined Patent Publication No.
A device having a special configuration disclosed in Japanese Patent No. 35978 is used.

Although the details of this apparatus will be described later, in this Example 1, in this apparatus, the above solid gas is injected from two injection nozzles having rectangular openings of 0.6 mm × 100 mm which are opposed to each other at a predetermined interval. A two-phase flow is jetted and the solid-gas two-phase flow jetted from both nozzles is blown to the center between these nozzles while moving the substrate 11 in the short side direction of the openings of these nozzles at a constant speed. Then, the above-mentioned dot-shaped irregularities 16 were formed. Fine unevenness 16 on the surface
The Co-Ni-
The magnetic film 13, the protective film 14, and the lubricating film 15 made of P were sequentially deposited and formed in the usual manner to obtain a magnetic disk 17.

Table 1 shows the conditions of Example 1, the conditions of Examples 2 to 5 in which the conditions were changed, and the results of performance measurement of the magnetic disks 17 obtained in Examples 1 to 5.

[Table 1] In (Table 1), the supply amount of abrasive grains is the nozzle opening area of 1 m.
The amount of supply per m ² is shown, and the processing time is the time for the opening to pass through the nozzle with respect to the surface to be processed. The surface roughness of the machined surface obtained on the disk substrate 11 is 40 μN using a stylus with a tip of 2.5 μm by using an ultra-precision roughness meter (Rank Taylor Hobson Co., Ltd.) as described above. Run on the surface by force, measuring length 0.49mm, cutoff 0.0
It was measured at 8 mm. Ra is the centerline average roughness, Rtm is the average value of the maximum amplitude in each cutoff, and Rpm is the average value of the centerline maximum peak heights in each cutoff, which is obtained as an indication of the roughness meter. Then, with respect to the magnetic disk 17 obtained by forming the magnetic film 13, the protective film 14, and the lubricating film 15 on the substrate 11, the dynamic friction coefficient before and after CSS, and C
The SS durability was measured.

The dynamic friction coefficient before CSS was measured by using a wear tester (made by Kubota Comps Co., Ltd.)
The rotation speed was set to 1 rpm, and the average value of the measured distances when the disk was rotated once was determined. The atmosphere at this time was 45% relative humidity and 23 ° C. temperature.

The coefficient of kinetic friction after CSS is obtained by using an actual machine having a drive device and a magnetic head, and using a disk 17
The rotation speed was set to 3600 rpm, and the frictional force was measured with a torque meter. The number of times of CSS is 20,000.
It was time. The atmosphere at this time is 50% or less in relative humidity,
The temperature was set to 23 ° C.

The CSS durability is the same as the method for measuring the dynamic friction coefficient after CSS, but the atmosphere at this time is 80% relative humidity, 30 ° C. temperature, and CSS until head adsorption.
The number of times was measured.

From these results, Examples 1 to 5 show that Ra
Is 60 ~ 230Å, Rtm is 520 ~ 2000Å, Rp
m has a surface roughness of 310 to 1300, and Rpm / Rt
It can be seen that it is preferable for the ratio of m to be 0.52 to 0.72.

In Table 1, Comparative Examples 1 and 2 are the cases where the conventional texture processing is applied, and the artificial leather is 1.0
Polished with an abrasive having an average particle diameter of μm to obtain a surface roughness Ra.
20 Å and then 0.8 and 1.0 with a soft cloth
It was polished in the circumferential direction using abrasive grains having an average grain size of μm. In Comparative Examples 3 and 4, conventional polishing, that is, artificial leather was used to polish grains having an average grain size of 0.8 μm and 1.0 μm. A magnetic disk having the same magnetic film 13, protective film 14, and lubricating film 15 as in Example 1 was formed using each magnetic disk substrate 11 thus obtained. Indicated.

As is apparent from Table 1, in the examples of the present invention, the dynamic friction coefficient and the CSS durability were equal to or higher than those of the conventional texture-processed ones.

On the other hand, in Comparative Examples 1 to 4, as described at the beginning, in order to avoid the occurrence of scratches and surface defects, it is necessary to set the surface roughness Ra to a small value of 20 to 100Å. Therefore, the coefficient of friction after CSS becomes as large as 0.45 to 0.70, and the durability may be lowered, which is not preferable.

The results of measurement of the surface roughness, that is, the profile, are shown in FIG. 5 for Example 1 of the present invention, FIG. 12 for Comparative Example 1, and FIG. 13 for Comparative Example 3.
As is clear by comparing these, it can be seen that the profile of Example 1 in FIG. 5 has a wider valley width than Comparative Example 1. Further, the surface of the disk substrate 11 obtained by the method of the present invention was observed by a microscope, and as a result, it was found that as shown in FIG. On the other hand, in the case of the texture processing, scratches were observed, and it was found that in the texture processing and the polishing processing, surface defects due to minute projections exist.

Next, the free abrasive grain jetting processing apparatus used in the method of the present invention for forming irregularities on the surface of the substrate 11 will be described. FIG. 6 is a cross-sectional view of a free abrasive grain jetting processing apparatus according to an embodiment of the present invention, FIG. 7 is a side view showing a part of the section, and 60 is a jetting processing container of this apparatus. An injection nozzle 50 whose opening end is a narrow rectangle is provided at the center. The injection nozzle 50 is connected to a pipe body 51 made of stainless steel, for example, to which N ₂ gas is supplied. Further, the tube body 51 is supplied with abrasive grains supply pipe 5 in which abrasive grains such as SiC are supplied.
Two are provided. The nozzle 50 is arranged in a ring 53, and the ring 53 is arranged as a workpiece so as to face the transition surface of the substrate 11. Reference numeral 54 represents an abrasive grain recovery tube. A pair of such devices are arranged in the container 60 so as to face each other on both sides of the substrate 11 or the workpiece.

A tube body 51 connected to the injection nozzle 50
Is supplied with dry nitrogen at 5-200 kPa. By doing so, the loose abrasive grains are sucked by the accelerated gas through the connecting portion of the abrasive grain supply pipe 52. Since fine abrasive grains of, for example, SiC having a particle diameter of about 0.5 to 5.0 μm are used here, the loose abrasive grains are sucked by the accelerated substrate, and flow toward the injection nozzle 50 as a solid-gas two-phase flow. , Sent in and spouted from this. In this case, a pressure of 0.1 to 1.3 kg / cm ² is also applied to the abrasive grain supply pipe 52. Here, the supply of loose abrasive particles in the solid-gas two-phase flow is 10
It is set to about g / min so that the direction of the jet flow jetted from the jet nozzle 50 is not disturbed.

Then, on the center plane between the pair of jet nozzles 50, the magnetic disk substrate 11 to be processed is conveyed to the substrate 11 by the conveying means 61 in the short axis direction of the opening shape of the nozzles 50.
Migrate along the plane of. In this way, the abrasive grains are jetted at a high pressure and impact on both surfaces of the substrate 11 of the workpiece to form fine dot-like irregularities.

The supply pressure of the fluid to the supply pipe body 51 was 5 to 200 kPa, and the unevenness could be formed without impregnating the Ni-P plating layer with the abrasive grains. The amount of abrasive grains supplied is 0.1 to 1.0 g per 1 mm ² of nozzle opening area.
Adjust within the range of / minute. Other adjustment items include the distance between the nozzle and the surface to be processed and the processing time.

Thus, according to the present invention,
Ra of 60 to 240 Å, Rtm of 500 to 2000 Å, Rpm of 300 to 1500 Å, R by spraying a solid gas two-phase flow in which abrasive grains are suspended in a gas having a pressure of kPa
It is possible to obtain a roughened disk substrate having a pm / Rtm of 0.5 to 0.75. A magnetic disk 17 having a metal magnetic film 13 on the disk substrate 11
Has improved the magnetic head's attractiveness and abrasion resistance.

On the other hand, the surface roughness Ra of the substrate is 60.
Less than Å, Rtm less than 500 Å,
When the ratio of Rpm / Rtm is less than 0.5, there is a problem that the magnetic head is likely to be attracted to the surface of the disk 17 due to insufficient roughness, and Ra exceeds 240Å and Rtm exceeds 2000Å. Cross over, Rpm / Rtm
If the ratio exceeds 0.75, the heights of the peaks become uneven due to processing, and the magnetic head oscillates, resulting in severe friction, which makes it impossible to sufficiently achieve low flying of the magnetic head.

Further, when the fluid pressure is 5 kPa or less, it is not possible to form the necessary unevenness on the Ni-P plated underlayer, and when it exceeds 200 kPa, the Ni-P plated underlayer is impregnated with abrasive grains. And surface defects such as scratches are formed, which is not preferable.

The substrate surface of the present invention is very superior to the conventional texture substrate surface in the following two points. There are few surface defects. This is more remarkable as the roughness is larger. The center line mountain height is large. In other words, Rpm / Rt
The ratio of m is large. The reason is that the processing method of the present invention does not create a new surface by applying only compressive force to the surface to be processed and grinding like a texture, and is because it is dry processing. Of course, in the case of the present invention, the processing is carried out under the condition that the embedding of abrasive grains does not occur. Further, the oxide film is extremely thin due to the processing in the inert gas. Has a definite difference from the conventional substrate surface,
The ratio of Rpm / Rtm in the present invention is as large as 1.5 to 2.5 times. This means that, for example, when contacting the slider of a floating magnetic head, the net contact area is small due to lack of directivity, and the friction coefficient is inevitably small.
Head adsorption is unlikely to occur. The surface texture of the substrate possessing these properties is maintained to some extent even if a medium layer and a protective film are attached, the head flying height can be reduced, high recording density can be easily achieved, and a magnetic disk with excellent head attraction resistance. Will be provided.

[0049]

As is apparent from the above description, the magnetic disk 17 obtained by subjecting the substrate 11 of the present invention to the medium processing satisfies the low friction coefficient and the adsorption durability of the disk surface with respect to the head required for the magnetic disk. At the same time, it is possible to achieve a low flying height of 0.1 μm or less on the disk surface of the magnetic head, and also a head hit failure (glide test failure).
Also, the signal error is reduced, and the product yield is improved.

The grounds for this are as follows. First, in the final processing of the substrate of the present invention, only a compressive force is applied to the surface to form minute irregularities so as to secure a predetermined roughness. Since it does not generate scraps, it has very few surface defects. This is more remarkable as the roughness is larger,
In other words, a rough substrate can be provided.

Secondly, the substrate surface of the present invention is characterized in that the ratio of Rpm / Rtm is larger than that of the conventional substrate.
That is, since the area of the bottom of the valley is larger than the area of the top of the peak, the coefficient of friction of the surface is small. This is more noticeable when a medium such as a magnetic film is processed on the surface of the substrate.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a surface state of a magnetic disk substrate according to the present invention.

FIG. 2 is a schematic cross-sectional view of an example of a magnetic disk according to the present invention.

FIG. 3 is a schematic sectional view showing a surface state of a magnetic disk according to the present invention.

FIG. 4 is a schematic pattern diagram of a magnetic disk substrate surface according to the present invention.

FIG. 5 is a measurement curve diagram of the surface roughness of the magnetic disk according to the present invention.

FIG. 6 is a plan sectional view of a loose abrasive jet processing apparatus.

FIG. 7 is a side view in which a part of the loose abrasive grain injection processing device is shown as a cross section.

FIG. 8 is a sectional view of a conventional magnetic recording disk.

FIG. 9 is a schematic cross-sectional view showing a surface state of a conventional magnetic disk substrate.

FIG. 10 is a schematic pattern diagram of a conventional textured surface.

FIG. 11 is a schematic cross-sectional view showing a surface state of a conventional magnetic disk.

FIG. 12 is a surface roughness measurement curve diagram of a conventional texture processing.

FIG. 13 is a surface roughness measurement curve diagram of a conventional texture processing.

[Explanation of symbols]

 11 Magnetic Disk Substrate 13 Magnetic Film 14 Protective Film 15 Lubrication Film 17 Magnetic Disk 21 Base 22 Underlayer

Claims (5)

[Claims] 1. A magnetic disk substrate surface is provided with a rough surface composed of fine dot-like irregularities, and the rough surface state has a center line average roughness Ra of 60 to 240Å and a maximum roughness Rtm of 500 to
2000Å, center line mountain height Rpm is 300-1500Å
And a surface roughness Rpm / Rtm of 0.5 to 0.75. 2. The magnetic disk substrate according to claim 1, wherein the magnetic disk substrate comprises a disk-shaped substrate made of aluminum or an aluminum alloy, and a Ni-P plated underlayer on the disk-shaped substrate. 3. The magnetic disk substrate according to claim 1, wherein the magnetic disk substrate comprises a disk-shaped substrate made of glass or ceramics. 4. A magnetic disk comprising the magnetic disk substrate according to any one of claims 1 to 3 and a magnetic film, a protective film, and a lubricating film sequentially deposited on the magnetic disk substrate. 5. A step of polishing the surface of a magnetic disk substrate having or not having a Ni—P underlayer on the surface, and thereafter, the average particle size of 0.5 to 5.0 on the polished surface.
A solid phase and a gas phase in which abrasive particles of μm are suspended in a fluid
A step of spraying a phase flow to form fine dot-like irregularities on the polished surface.