JP2000132829A - Glass substrate for magnetic recording medium, magnetic recording medium and their production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain high electromagnetic conversion characteristics and CSS durability by controlling the surface roughness of the principal plane by bringing the max. height, center line roughness and the ratio of these values measured by an atomic force microscope(AFM) into specified ranges. SOLUTION: When the surface roughness on at least the principal plane of a glass substrate is measured by an AFM, the surface has 0.2 to 2.5 nm Ra, 3 to 25 nm Rmax and 3 to 35 Rmax/Ra so that the obtd. glass substrate for a magnetic recording medium such as a magnetic disk has <=1.2 μ inch glide height, thereby preventing a magnetic head to cling to the glass substrate. Here, Ra and Rmax stand for line roughness and the max. height, respectively, each specified by JIS B0601. The ratio Rmax/Ra measured by an AFM indicates the distribution (uniformity or scatter) of the height of projections on the rugged substrate surface. The glass substrate contains at least alkali metal oxides and <3 mol% alkaline earth oxides.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic recording medium glass substrate constituting a magnetic recording medium such as a hard disk,
The present invention relates to a magnetic recording medium using the glass substrate for a magnetic recording medium and a method for manufacturing the same.

[0002]

2. Description of the Related Art In the technical field of magnetic recording and reproduction,
The interface between the magnetic head and the magnetic disk has become one of the key technologies for improving the recording capacity. In order to improve the recording density, the flying height of the magnetic head flying above the surface of the magnetic disk (flying height)
However, in the case of performing a CSS (contact start / stop) recording / reproducing, there is a high possibility that the magnetic head is attracted to the magnetic disk (stiction) as the flying height of the magnetic head is reduced. Become.

In order to prevent such a magnetic head from being attracted, various texture techniques have been conventionally proposed. As a typical example, there is a method in which the surface of an Al / NiP plated substrate is formed into an irregular shape by mechanical polishing (Japanese Patent Laid-Open No. 62-273719). In the case of a glass substrate having better flatness than an aluminum substrate, a method of forming a thin film having an uneven surface by sputtering on a glass substrate (Japanese Patent Publication No. 4-62413) or a method of forming unevenness by chemical etching (Tokuhei 7-1015
07) has been proposed.

[0004]

By the way, recently,
With the aim of improving the recording capacity, the glide height has reached a stage of 1.2 μ inch or less. However, the method of forming the above-described texture that has been conventionally proposed,
This was a texture technique under conditions where the glide height was about 8 μ inches. Therefore, it has been difficult to obtain a magnetic disk that satisfies both the sufficient electromagnetic conversion characteristics and the effect of preventing the magnetic head from being attracted at the same time, even when applied to a magnetic disk that records and reproduces data at a low flying height as in today. .

Since the conventional glide height is about 8 μ inch, the surface condition of the magnetic disk (substrate) is evaluated by scanning a stylus having a radius of several μm (for example, 2.5 μm) on the surface. The evaluation by the tally step for measuring the roughness was sufficient, but 1.2 μm as currently required.
When the flying height becomes less than inches (1 inch = 25.4 mm), it is difficult to judge whether or not the state of the glass substrate surface is sufficient to prevent the magnetic head from being attracted by the evaluation using the tally step. It is a situation.

SUMMARY OF THE INVENTION The present invention has been made in view of the above background, and has a glide height of 1.2 μ inch or less, a high electromagnetic conversion characteristic, and a high CSS durability characteristic. It is an object of the present invention to provide a glass substrate for a magnetic recording medium constituting a medium and a method for manufacturing the same.

[0007]

Means for Solving the Problems The present inventors have focused on specifying the surface state of a glass substrate by using an atomic force microscope (AFM) in order to evaluate the appropriate surface state of the glass substrate surface. . This is because the resolution is low in the conventional stylus-type measuring method, and it is not possible to determine whether the surface state of the glass substrate is appropriate. Based on this evaluation method, in order to achieve the above object, the height and distribution (variation in height) of the convex portions in the fine irregularities formed on the main surface of the glass substrate are important factors. Clarified that. In addition, as a result of repeating various experiments, polishing conditions,
It has been found that the target glass substrate surface cannot be obtained unless the surface treatment conditions are set to a specific combination. The present invention is based on such an elucidation result. According to the first invention, at least the surface roughness of the main surface is Ra (center line average roughness) when measured by an atomic force microscope (AFM). =
0.2-2.5 nm, Rmax (maximum height) = 3-25
nm, and Rmax / Ra = 3 to 35. A glass substrate for a magnetic recording medium.

According to a second aspect, in the glass substrate for a magnetic recording medium according to the first aspect, the main surface of the glass substrate for a magnetic recording medium is parallel to a virtual main surface when the main surface is assumed to be completely flat. When the surface is an isosurface, and the irregular surface formed on the main surface of the magnetic recording medium glass substrate is cut by the isosurface, the entire virtual main surface with respect to the sum of the areas of the cut surfaces is obtained. The bearing ratio is defined as a percentage of the area value of the area defined as a percentage, and the contour surface having the bearing ratio of 50% is defined as a reference plane,
The distance from this reference plane to the contour surface having each bearing ratio is defined as the bearing height, and the bearing height of the contour surface, which is 2.5% of the bearing ratio, is defined as B.B. H.
(2.5) The bearing height on the contour surface, which is 5.0% of the bearing ratio, H. (5.0), B.I. H.
(2.5) /Rmax=0.1 to 0.5, or H.
(5.0) /Rmax=0.1 to 0.45. A glass substrate for a magnetic recording medium.

[0009] In a third aspect of the present invention, at least the surface roughness of the main surface is determined by Rm when measured by an atomic force microscope (AFM).
ax = 3 to 25 nm; H. (2.5) / R
max = 0.1-0.5 or B.I. H. (5.0) / Rmax
= 0.1 to 0.45. It is a glass substrate for a magnetic recording medium. (However, BH (2.5) and BH (5.0) are as defined in claim 2)

A fourth invention is a glass substrate for a magnetic recording medium according to any one of the first to third inventions, wherein the glass substrate contains at least an alkali metal oxide. According to a fifth aspect, in the glass substrate for a magnetic recording medium according to any one of the first to third aspects, the glass substrate contains at least an alkali metal oxide and less than 3 mol% of an alkaline earth oxide. A glass substrate for a magnetic recording medium. A sixth invention provides a glass substrate for a magnetic recording medium according to any one of the first to fifth inventions, wherein the glass substrate is used for a magnetic disk having a glide height of 1.2 μ inch or less. It is a glass substrate.

A seventh invention is a magnetic recording medium characterized in that at least a magnetic layer is formed on the main surface of the glass substrate for a magnetic recording medium according to any one of the first to sixth inventions. .

An eighth invention relates to an atomic force microscope (AFM).
The surface roughness of the main surface as measured by Ra = 0.1 to
A glass substrate having a thickness of 1.0 nm is prepared, and the surface roughness of at least the main surface of the glass substrate is Ra = 0.2 to 2.5 n.
m, Rmax = 3 to 25 nm, Rmax / Ra = 3 to 3
5. A method for producing a glass substrate for a magnetic recording medium, wherein the glass substrate is subjected to a chemical surface treatment to obtain a glass substrate.

According to a ninth invention, the surface roughness of the main surface as measured by an atomic force microscope (AFM) is Ra = 0.1-1.
A method for producing a glass substrate for a magnetic recording medium, comprising preparing a glass substrate having a thickness of 0 nm, and subjecting at least the main surface of the glass substrate to a surface treatment with silicic acid.

According to a tenth aspect of the present invention, in the method for manufacturing a glass substrate for a magnetic recording medium according to the eighth or ninth aspect, at least the glass substrate is subjected to the chemical surface treatment or the surface treatment with silica hydrofluoric acid. 0.3-3.
A method for producing a glass substrate for a magnetic recording medium, wherein the polishing is performed using an abrasive containing free abrasive grains having a particle diameter of 0 μm.

According to an eleventh invention, in the method for manufacturing a glass substrate for a magnetic recording medium according to the tenth invention, the chemical surface treatment or the surface treatment with silicic acid is carried out in the polishing step of the glass substrate. A method for manufacturing a glass substrate for a magnetic recording medium, characterized in that a portion having a relatively high residual strain in a residual stress distribution generated at a position of a polishing locus due to grains is processed into a convex portion. .

According to a twelfth aspect, in the method for manufacturing a glass substrate for a magnetic recording medium according to any one of the ninth to eleventh aspects, the concentration of the silicic acid is 0.15 to 3.0.
% By weight of a glass substrate for a magnetic recording medium.

According to a thirteenth invention, in the method for manufacturing a glass substrate for a magnetic recording medium according to any one of the eighth to twelfth inventions, the glass constituting the glass base material comprises at least an alkali metal oxide and an alkaline earth metal. Containing oxides of a kind and the total content of alkaline earth oxides is 3 mo
A method for producing a glass substrate for a magnetic recording medium, wherein the glass substrate content is less than 1%. A fourteenth invention is directed to the method of manufacturing a glass substrate for a magnetic recording medium according to the thirteenth invention, wherein the glass constituting the glass base material is made of SiO2.
8 to 75% by weight, 5 to 23% by weight of Al2 O3, Li2
A method for manufacturing a glass substrate for a magnetic recording medium, characterized in that the glass is a glass containing 3 to 10% by weight of O and 4 to 13% by weight of Na2 O as a main component.

According to a fifteenth aspect of the present invention, in the method for manufacturing a glass substrate for a magnetic recording medium according to the fourteenth aspect, the glass constituting the glass substrate contains 62 to 75% by weight of SiO2 and 5 to 15% of Al2 O3. % By weight, 4-10
% By weight, 4 to 12% by weight of Na2 O, and 5.5 of ZrO2.
-15% by weight, containing Na2
O / ZrO2 weight ratio of 0.5 to 2.0, Al2 O3 /
A method of manufacturing a glass substrate for a magnetic recording medium, wherein the glass is a glass having a weight ratio of ZrO2 of 0.4 to 2.5.

According to a sixteenth invention, in the method for manufacturing a glass substrate for a magnetic recording medium according to any one of the eighth to fifteenth inventions, a chemical strengthening treatment is performed after the chemical surface treatment or the surface treatment with silicic acid. A method for manufacturing a glass substrate for a magnetic disk.

A seventeenth invention is directed to a magnetic recording medium glass substrate manufactured by the method for manufacturing a magnetic recording medium glass substrate according to any one of the eighth to sixteenth inventions, wherein:
A method for manufacturing a magnetic recording medium, comprising forming at least a magnetic layer.

According to an eighteenth aspect, for each type of magnetic head,
The surface condition of the glass substrate for a magnetic recording medium for improving the flying characteristics of the magnetic head is specified in the range of values of Ra, Rmax and Rmax / Ra measured by an atomic force microscope (AFM). R obtained when the surface of a glass substrate is surface-treated under various surface treatment conditions and the surface state after the treatment is measured by an atomic force microscope (AFM).
a, Rmax, and Rmax / Ra, the surface treatment conditions when the respective values fall within the above specific ranges are determined, and the surface of the glass substrate for a magnetic recording medium is surface-treated by the determined surface treatment conditions. Of manufacturing a glass substrate for a magnetic recording medium.

According to the first aspect, when the surface roughness of at least the main surface of the glass substrate is measured by AFM, Ra = 0.2 to 2.5 nm and Rmax = 3 to 25 n
By setting m and Rmax / Ra = 3 to 35, it is possible to obtain a glass substrate for a magnetic recording medium such as a magnetic disk having a glide height of 1.2 μ inch or less and having no magnetic head attracted. In the case of a CSS type magnetic disk, a glass substrate for a magnetic recording medium such as a magnetic disk which satisfies even higher CSS durability characteristics can be obtained. Here, Ra and Rmax are respectively JIS B
0601 are the center line average roughness and the maximum height.

The value of Rmax measured by AFM indicates the maximum height of the unevenness formed on the substrate surface, and Rmax is 3n.
If it is less than m, the surface of the substrate will be in a state close to a mirror state, and for example, the magnetic head will be undesirably attracted to the surface of the magnetic disk. If Rmax exceeds 25 nm, the glide height exceeds 1.2 μ inch, which is not preferable.

The ratio of Rmax / Ra measured by AFM is an important factor because it indicates the distribution (variation (uniformity)) of the heights of the protrusions on the surface of the substrate and changes the friction coefficient. . The present inventors have found that there is an appropriate range for the variation in the height of the projections of the concavities and convexities for realizing high CSS durability characteristics while maintaining the glide height of 1.2 μ inch or less. .

When Rmax / Ra indicating the distribution (variation) of the heights of the projections is less than 5, the unevenness becomes relatively uniform, the static friction coefficient exceeds 3, and the contact area of the magnetic head increases. It is not preferable because it is easy to be adsorbed and the CSS durability is deteriorated.

Further, when Rmax / Ra exceeds 35, it means that the maximum height of the projections with respect to the entire average surface roughness becomes large, the coefficient of static friction becomes 1 or less, and the contact area of the magnetic head decreases. However, since the load on the largest convex portion increases, a head crash occurs, which is not preferable.

As a recording / reproducing method of a magnetic disk, CS
There are an S method and a load / unload (ramp load) method. For example, in the case of the CSS method, Ra = 0.2 to 2..
5 nm, Rmax = 5 to 25 nm, Rmax / Ra = 5
-35, preferably Ra = 0.7-1.5 nm, Rma
x = 8 to 18 nm, surface roughness is controlled within the range of Rmax / Ra = 10 to 20, and in the case of the load / unload method, specifically, Ra = 0.2 to 2.5 nm, Rmax
= 3 to 10 nm, and the surface roughness is controlled within the range of Rmax / Ra = 3 to 15. The irregularities formed on the surface of the glass substrate of the present invention have a texture function for preventing attraction with the magnetic head.

As described above, Rmax / Ra is a parameter indicating the distribution (variation (uniformity)) of the projections and depressions on the surface of the substrate. Although it is certain that a high CSS durability characteristic can be obtained, actually, the protrusions on the surface of the magnetic disk which directly contact the magnetic head are high protrusions equivalent to Rmax which is the maximum protrusion height among the protrusions and recesses on the substrate surface. It is important to control the ratio (distribution) of the high protrusions in order to further lower the flying height and to obtain high CSS durability characteristics. Therefore, the parameter B.B., which is a parameter indicating the proportion of high protrusions equivalent to Rmax, which is the maximum protrusion height of unevenness on the substrate surface, is used. H. The ratio of / Rmax becomes very important.

According to the second or third aspect of the present invention, the contour surface having a bearing ratio of 50% is used as a reference surface, and the height from the reference surface is defined as the bearing height. Bearing ratio 2.5% bearing height B. H. (2.5), bearing ratio 5.0%
The bearing height of B. H. (5.0), B.I.
H. (2.5) /Rmax=0.1-0.5, or H.
It is preferable to set (5.0) /Rmax=0.1 to 0.45 because further lowering of the flying height can be realized and high CSS durability characteristics can be obtained.

Here, the bearing ratio and the bearing height will be described. FIG. 1 is a measurement photograph when the surface roughness of the main surface of the glass substrate for a magnetic disk obtained by the present invention is measured by an atomic force microscope (AFM).
FIG. 2 is a measurement curve showing surface irregularities on a specific straight line on the surface shown in FIG. Now, a virtual main surface is assumed assuming that the main surface of the glass substrate is completely flat, and a plane parallel to the virtual main surface is defined as a contour plane. The contour plane whose distance from the virtual main surface is within a predetermined range cuts the irregularities formed on the main surface of the glass substrate. The ratio of the total area of the virtual main surface to the sum of the areas of the cut surfaces of all the concavities and convexities cut by the contour surface expressed as a percentage is defined as a bearing ratio.

Further, a contour surface at which the bearing ratio is 50% is defined as a reference surface, and a distance from the reference surface to a contour surface having each bearing ratio is defined as a bearing height.

The above bearing ratio is plotted on the horizontal axis,
The vertical distance of the contour plane at that time from the highest point, that is, the depth (bearing depth) is plotted on the vertical axis, and is called a bearing curve. FIG. 3 shows a bearing curve of the surface unevenness shown in FIG. The bearing ratio is 5
The contour plane at a depth of 0% is the reference plane.

The bearing height at which the bearing ratio becomes 2.5% is defined as B.I. H. (2.5) The bearing height at which the bearing ratio becomes 5.0% is defined as B. H. (5.0).

In such a case, B.I. H. (2.5) / Rmax
= 0.1 to 0.5, or B.I. H. (5.0) / Rmax =
It has been found that when the ratio is 0.1 to 0.45, further lowering of the flying height can be realized and high CSS durability characteristics can be obtained.

B. Measured by AFM H. The ratio of / Rmax relatively indicates the ratio (distribution) of the height and the maximum protrusion height at a certain bearing value, and is closely related to the protrusion density. As a result of various experiments, the present inventors found that B.I. H. / Rmax value is CS
It has been found that there is a close relationship between S durability and the coefficient of static friction. That is, B. H. (2.5) / Rmax, B.R. H. (Five.
0) When / Rmax is less than 0.1, the friction coefficient increases largely due to sliding, and the CSS durability is low. Also,
B. H. (2.5) / Rmax, B.R. H. (5.0) / Rmax
Exceeds 0.5 and 0.45, respectively, the coefficient of friction exceeds 3, which is not preferable.

In this case, the plane having a bearing ratio of 50% in the bearing curve is used as the reference plane, but this is for defining the reference plane of the bearing height.
This reference plane may take any bearing ratio value in the bearing curve. However, the case where the bearing ratio is 50% is preferable because it is the center plane of the convex and concave portions in the irregularities on the main surface of the glass substrate.

The bearing height (BH) is set to a value of 2.5% or 5.0% by the bearing ratio because of the low flying height and low friction required for the magnetic disk. This is because the coefficient and the ratio of the density of the convex portions having a height equivalent to the maximum surface roughness that comes into contact with the magnetic head, which is associated with the high CSS durability, can be accurately identified.

Table 1 shown in FIG. 4 shows a plurality (four) of magnetic disks of which the density of the protrusions was previously measured by AFM (the protrusions when sliced 6 nm from the average line of the surface roughness). 380 pieces (disk A), 96 pieces (disk B), 64 pieces (disk C), 0 pieces (disk D) are prepared, and the bearing ratio is 0.025% and 0.25%, respectively. 2.5%, 5.0%, 2
B. 5% H. It shows the result of calculating / Rmax.

B. shown in Table 1 of FIG. H. / Rmax
Can be said to be a relative representation of the ratio of the protruding portions. When the bearing ratio is set to 0.025% and 0.25%, the disk A> Disk B> Disk C> Disk D must be satisfied. H. The value of / Rmax is larger than that of disk A or disk B. This is considered to be because the bearing ratio takes into account a relatively small value, that is, only a very small area of the convex portion is considered, so that the ratio of the number of abnormal projections irrelevant to the glide characteristic is included in a large amount. . Therefore, in this case, it is not preferable because the ratio of the convex portions cannot be identified.
In the case of a bearing ratio of 25%, the ratio of the density of the convex portions can be identified, but the B.D. H. / Rm
This is not preferable because the range of ax is small.

The above results are summarized as follows, and the second and third inventions are based on these results. (1) The bearing curve of the unevenness of the surface of the substrate is obtained, and a reference plane serving as a reference of the bearing height is determined. In the case of the second invention and the third invention, the depth is such that the bearing ratio is 50%. (2) Bearing height measured from the reference plane determined in 1 above. H. And the ratio of Rmax (BH / Rma
x) is a characteristic required for a magnetic disk or a specific parameter indicating the state of surface unevenness corresponding to this characteristic. H. A bearing ratio that can be accurately identified by the value of / Rmax is selected. In the case of the second invention and the third invention, the bearing which can accurately identify the ratio of the convex portion on the substrate surface corresponding to the characteristics required for the magnetic disk, such as the glide height, the friction coefficient, and the CSS durability. Ratio values (2.5%, 5.0%) are selected. (3) The bearing ratio selected in the above item 2 satisfies the characteristics required for the magnetic disk. H.
Determine the range of / Rmax. In the case of the second invention and the third invention, B.G.
H. (2.5) /Rmax=0.1-0.5, or H.
(5.0) /Rmax=0.1 to 0.45.

The glass substrate for a magnetic disk manufactured by such a method for managing the surface roughness is useful for a magnetic disk that requires strict control of the surface roughness of the substrate, such as a further reduction in the flying height of a magnetic head. is there. Further, according to the fourth aspect, the above-mentioned glass substrate contains at least an alkali metal oxide, so that the above-mentioned glass substrate is subjected to a chemical surface treatment (silica hydrofluoric acid treatment or the like) to form the above-mentioned (first glass substrate).
To the third invention) can be easily obtained.

According to the fifth invention, the above-mentioned glass substrate contains at least an alkali metal oxide and an alkaline earth oxide, and the content of the alkaline earth oxide is 3%.
When the content is less than mol%, the desired surface roughness described above (the first to third inventions) can be easily obtained by a chemical surface treatment (silica hydrofluoric acid treatment or the like) as described later. Further, according to the sixth aspect, by using the magnetic disk having a glide height of 1.2 μ inch or less for recording and reproduction, the effect is maximized in high recording density and high CSS durability. Is done.

According to the seventh aspect, at least a magnetic layer is formed on the main surface of the above-mentioned glass substrate,
A magnetic disk satisfying high electromagnetic conversion characteristics and high CSS durability characteristics can be obtained.

According to the eighth aspect, the surface roughness of the main surface as measured by AFM is Ra = 0.1 to 1.0 n.
m, and at least the main surface of the glass substrate has a surface roughness of Ra = 0.2 to 2.5 nm, Rma
By performing a chemical surface treatment such that x = 3 to 25 nm and Rmax / Ra = 3 to 35, a glass substrate for a magnetic disk satisfying high CSS durability characteristics can be stably manufactured.

Further, according to the ninth aspect, the surface roughness of the main surface as measured by AFM is Ra = 0.1 to 1.0 n.
m, and at least the main surface of the glass substrate is surface-treated with silica hydrofluoric acid to obtain a high CS.
A glass substrate for a magnetic disk satisfying the S durability characteristic can be stably manufactured. In order to stably manufacture a glass substrate for a magnetic disk that satisfies high CSS durability characteristics, the surface roughness of the glass substrate before surface treatment is set to a predetermined roughness (Ra = 0.1 to 1.0 nm). In addition, it is necessary to select a chemical to be surface-treated as silicic acid.

In order to stably manufacture the glass substrate for a magnetic disk of the present invention, which requires high-precision control of the surface roughness, the present inventors require the surface roughness of the glass substrate before the surface treatment. Has a great influence on the height distribution (variation) of the projections on the finally obtained substrate surface. As a result of intensive studies, it is preferable that the surface of the glass substrate before the surface treatment is in a mirror surface state.
= 0.1 to 1.0 nm. Desirably, Ra = 0.1 to 1.0 nm, Rma
It was found that x should be set to 1 to 20 nm.

The hydrofluoric acid used for treating the surface of the glass substrate of the present invention has a lower etching power than hydrofluoric acid or hydrofluoric acid aqueous solution containing potassium fluoride which has been conventionally used as an etching solution. Since the etching rate is low), it is possible to control the surface roughness with high accuracy. A typical example of hydrofluoric acid is hydrofluoric acid (H2 SiF6). The silicon hydrofluoric acid treatment liquid may contain other acids (such as hydrofluoric acid, sulfuric acid, hydrochloric acid, and nitric acid) in a small amount to enhance the etching (cleaning) effect and the like.
A commercially available detergent (a neutral detergent, a surfactant, an alkaline detergent, and the like) may be added.

The treatment conditions of the hydrofluoric acid are determined mainly by the hydrofluoric acid concentration, the immersion time in the hydrofluoric acid, and the temperature of the hydrofluoric acid. The hydrofluoric acid is obtained by dissolving hydrofluoric acid in water, and the hydrofluoric acid concentration refers to the concentration of hydrofluoric acid dissolved in water. The hydrofluoric acid concentration and the temperature are related to the etching rate (a specific range will be described later), and the immersion time in the hydrofluoric acid is related to the obtained roughness and the tact time of the process.
The treatment conditions of these hydrofluoric acids mainly depend on the surface roughness Rma
The surface roughness Rmax increases as the concentration of silica hydrofluoric acid increases, the immersion time in silica hydrofluoric acid increases, and the temperature of silica hydrofluoric acid increases. The treatment conditions of the above-mentioned hydrofluoric acid are appropriately adjusted depending on the roughness of the surface irregularities to be formed, and the immersion time in the hydrofluoric acid is 50 to 60.
The temperature of the silicic acid for 0 sec is preferably 15 ° C to 60 ° C from the viewpoint of controllability of the surface roughness.

According to the tenth aspect, the glass substrate is obtained by polishing at least the main surface of the glass substrate before the surface treatment with free abrasive grains having a particle diameter of 0.3 to 3.0 μm. Shall be polished with an agent. The particle size is mainly correlated with the surface roughness Ra, and when the average particle size of the abrasive grains is increased,
The surface roughness Ra of the glass substrate after the silica hydrofluoric acid treatment is increased (however, at this time, the surface roughness Rmax hardly changes). By setting the particle size to 0.3 to 3.0 μm, a preferable density of the convex portion and a tip shape of the convex portion in contact with the magnetic disk can be obtained, so that a glass substrate for a magnetic disk with higher CSS durability can be provided. it can.

When the particle size of the free abrasive grains is less than 0.3 μm,
Agglomeration of the abrasive is likely to occur, and the residue after the washing step is increased.
It is not preferable because roughness after etching becomes too large.

The free abrasive grains include cerium oxide (CeO2), alumina (Al2 O3), colloidal silica (SiO2), iron (Fe2 O3), chromium oxide (Cr2 O3), zirconium oxide (ZrO2), and titanium oxide. (TiO2).

Further, in the eleventh invention, the chemical surface treatment or the surface treatment with silica hydrofluoric acid is relatively performed in the residual stress distribution generated at the locus of the free abrasive grains in the polishing step of the glass base material. The processing is performed so that a portion having a high residual distortion becomes a convex portion.

The present inventors have discovered that when the surface is treated with silica hydrofluoric acid after polishing with an abrasive containing free abrasive grains, the trajectory of the free abrasive grains tends to be formed as a projection. Although the mechanism is not clear, the load of the polishing process is applied to the surface of the glass substrate by the free abrasive grains, which causes a structural change in the Si—O network of the glass from a histological point of view. This is considered to cause unevenness in the residual stress distribution and to reduce the etching rate by silicic hydrofluoric acid at a location where the residual strain is relatively high.

The ninth to eleventh inventions positively utilize the phenomenon according to the above-mentioned discovery, and thereby make it possible to obtain a desired surface roughness state for the first time.

The concentration of the above-mentioned hydrofluoric acid is 0.15 to 3.0.
% By weight (twelfth invention).
It is preferable that the electric conductivity of the silicic acid is 2 to 30 ms / cm. When the concentration of the silicic acid is less than 0.15% by weight, the etching effect and the cleaning effect on the glass substrate are reduced, and the desired surface roughness cannot be formed. When the concentration exceeds 3.0% by weight, Since the etching rate is increased, it is difficult to control the surface roughness with high accuracy, and a glass substrate for a magnetic recording medium having a stable quality cannot be obtained, which is not preferable.

If the projections as in the first to third aspects of the present invention are formed, the type of the glass substrate used in the present invention,
The size, thickness and the like are not particularly limited. Examples of the material of the glass substrate include aluminosilicate glass, soda lime glass, sodaaluminosilicate glass, aluminoborosilicate glass, borosilicate glass, and quartz glass. Above all, silicic acid has particularly good controllability of chemical etching with respect to aluminosilicate glass, and enables highly accurate control of surface roughness.

Further, the glass substrate (glass substrate for forming the convex portion by the mechanism as in the eleventh invention) used in the manufacturing method of the present invention contains at least an alkali metal oxide and contains The total content of earth oxides (RO: MgO, CaO, etc.) is 3 mo
It is preferable that the composition be less than 1% of the material (the thirteenth invention).
It is preferable to use a material containing as a main component l2 O3: 5 to 23% by weight, Li2 O: 3 to 10% by weight, and Na2 O: 4 to 13% by weight (a fourteenth invention).

In order to make the formation of the projections more remarkable by the mechanism as in the eleventh invention, it is necessary to use CaO or Mg.
It is desirable that the glass does not contain an alkaline earth (metal) oxide such as O. In particular, as in the fifteenth invention, the composition of the glass substrate is as follows: SiO2: 62 to 75% by weight, Al2 O3: 5 to 15% by weight, Li2 O: 4-1.
0% by weight, Na2 O: 4 to 12% by weight, ZrO2: 5.
5 to 15% by weight as a main component,
The weight ratio of 2 O / ZrO 2 is 0.5 to 2.0, and Al 2 O 3
Aluminosilicate glass having a weight ratio of / ZrO2 of 0.4 to 2.5 is preferred. By chemically strengthening such aluminosilicate glass,
This is preferable because the transverse rupture strength is increased, the depth of the compressive stress layer is deep, the Knoop hardness is excellent, and the controllability of etching in the surface treatment with silica hydrofluoric acid is very excellent. Note that N5 manufactured by HOYA CORPORATION is a typical example of the above-mentioned aluminosilicate glass.

Further, by performing the surface treatment with the hydrofluoric acid in at least two stages, or by using different hydrofluoric acid concentrations in each stage, the fine surface roughness of the substrate surface can be controlled. .

It is preferable to carry out a chemical strengthening treatment after the chemical surface treatment or the surface treatment with silicic acid (the sixteenth invention). Here, as the chemical strengthening method,
There is no particular limitation as long as it is a conventionally known chemical strengthening method. For example, from the viewpoint of the glass transition point, a low-temperature ion exchange method in which ion exchange is performed in a region not exceeding the transition point temperature is preferable. As the alkali molten salt used for chemical strengthening,
Potassium nitrate, sodium nitrate, or a nitrate obtained by mixing them is mentioned.

In the case where the surface treatment with the above-mentioned silica hydrofluoric acid is performed immediately after the surface of the glass substrate is chemically strengthened, the residual strain formed by the free abrasive grains on the surface of the glass substrate is reduced by the chemical strengthening treatment. Since the surface roughness cannot be controlled because it is buried in the stress, it is not preferable. However, between the chemical strengthening treatment step and the surface treatment step with silica hydrofluoric acid (before the surface treatment with silica hydrofluoric acid), as in the case of chemical strengthening treatment → polishing treatment with free abrasive grains → surface treatment with silica hydrofluoric acid, The same effect as described above can be obtained by including a polishing process using particles.

According to the seventeenth aspect, high electromagnetic conversion can be achieved by forming at least a magnetic layer on the main surface of the glass substrate manufactured by the above-described method for manufacturing a glass substrate for a magnetic recording medium such as a magnetic disk. A magnetic recording medium such as a magnetic disk which satisfies the characteristics and the high CSS durability characteristics can be obtained.

According to the eighteenth aspect, Ra, Rm indicating the height of unevenness measured by an atomic force microscope (AFM).
a, by controlling the surface roughness of the main surface of the glass substrate so that Rmax / Ra indicating the height distribution of the irregularities falls within a specific range, a magnetic disk or the like that satisfies high electromagnetic conversion characteristics and high CSS durability characteristics. A glass substrate for a magnetic recording medium to be used is obtained. Also, as in the following configurations (a) and (b), the bearing height indicating the ratio (distribution) of the projections having a height corresponding to the maximum projection height has a specific value, and the bearing height on the isosurface has a specific value. (BH) / Rmax (BH / Rmax), or Ra, Rmax, Rm
ax / Ra, B.A. H. By controlling the surface roughness of the main surface of the glass substrate so that / Rmax is in a specific range, a glass substrate for a magnetic recording medium used for a magnetic disk or the like satisfying high electromagnetic conversion characteristics and high CSS durability characteristics. Is obtained. (A) For each type of magnetic head, the bearing height (B.H.H.) when the surface condition of the glass substrate for a magnetic recording medium for improving the flying characteristics of the magnetic head is measured by an atomic force microscope (AFM). ) And Rmax (BH / Rmax)
x), the surface of the glass substrate for a magnetic recording medium is surface-treated under various surface treatment conditions, and the surface state after the treatment is measured by an atomic force microscope (AFM). . H. Wherein the surface treatment conditions are determined when the value of / Rmax falls within the above specific range, and the surface of the magnetic recording medium glass substrate is surface-treated by the determined surface treatment conditions. Substrate manufacturing method. (However, the bearing height (BH) is the content defined in claim 2). (B) For each type of magnetic head, a glass substrate for a magnetic recording medium that improves the flying characteristics of the magnetic head. , Rma when the surface state of is measured by an atomic force microscope (AFM).
x, Rmax / Ra, bearing height (BH) and R
The surface of the glass substrate for a magnetic recording medium is subjected to surface treatment under various surface treatment conditions, and the surface state after the treatment is determined using an atomic force microscope (AH). AFM), Ra, Rmax,
Rmax / Ra, B.R. H. Wherein the surface treatment conditions are determined when the value of / Rmax falls within the above specific range, and the surface of the magnetic recording medium glass substrate is surface-treated by the determined surface treatment conditions. Substrate manufacturing method. (However, bearing height (BH)
Is the content defined in claim 2. )

[0064]

(Embodiment 1) FIG. 5 is a schematic sectional view showing the structure of a magnetic disk according to Embodiment 1 of the present invention. As shown in FIG. 5, the magnetic disk of this embodiment has a glass substrate 1 on which a seed layer 2, an underlayer 3, a magnetic layer 4, a protective layer 5, and a lubricating layer 6 are sequentially formed.

The glass substrate 1 was composed of 63.5% by weight of SiO 2, 14.2% by weight of Al 2 O 3, and 10.4% of Na 2 O.
Wt%, Li2O: 5.4 wt%, ZrO2: 6.0 wt%, Sb2O3: 0.4 wt%, As2O3: 0.1
Aluminosilicate glass having a composition of weight%, having an outer diameter of 65 mmφ, a central hole diameter of 20 mmφ, and a thickness of 0.63.
It was processed into a 5 mm disk shape. The two main surfaces, the end surface and the chamfered portion are precisely polished and surface-treated with silica hydrofluoric acid, so that the surface roughness of both main surfaces is Ra =
1.3 nm, Rmax = 14.1 nm, Rmax / Ra
= 10.8, B.I. H. (2.5) = 6.02 nm; H.
(5.0) = 4.33 nm; H. (2.5) / Rmax =
0.43, B.I. H. (5.0) /Rmax=0.31.

The seed layer 2 is made of NiA having a thickness of 40 nm.
1 (Ni: 50 at%, Al: 50 at%) film.
Since the seed layer 2 has a small crystal grain size and excellent uniformity, the underlayer 3 and the magnetic layer 4 formed thereon are formed.
Has a fine crystal grain size and plays a role in reducing noise.
As the seed layer, in addition to NiAl described above, NiAl
NiAlRu, NiAlNd, N
iAlW, NiAlTa, NiAlHf, NiAlM
o, NiAlCr, NiAlZr, NiAlNb and the like.

The underlayer 3 is made of CrMo (C
r: 94 at%, Mo: 6 at%) film. The underlayer 3 preferably reduces the difference in the crystal lattice spacing of the magnetic layer 4 formed thereon as much as possible, and plays a role in improving the coercive force. Examples of the underlayer include Cr, CrV, and the like in addition to CrMo described above. Preferably, matching with the lattice spacing of the seed layer 2 is preferable because crystal growth becomes good and electromagnetic conversion characteristics become good. Further, the underlayer is not limited to a single layer, and may have a plurality of layers in which the same or different layers are stacked. For example, Cr
/ CrMo, Cr / CrV, CrV / CrV, etc.

The magnetic layer 4 is made of CoPtCr having a thickness of 27 nm.
Ta (Co: 75 at%, Cr: 17 at%, Pt: 5
at%, Ta: 3 at%) film. The material of the magnetic layer in the magnetic disk of the present invention is not particularly limited. As the magnetic layer, specifically, CoPt, CoCr, CoNiCr, CoCrTa, C
oPtCr, CoNiPt, CoNiCrPt, CoN
A magnetic thin film such as iCrTa or CoCrTaPtNb can be used.

The magnetic layer has a multilayer structure (for example, CoCrPtTa / C) in which the magnetic film is divided by a non-magnetic film (for example, Cr, CrMo, CrV, etc.) to reduce noise.
rMo / CoCrPtTa). Also,
As the magnetic layer, in addition to the above-mentioned Co-based, ferrite-based,
A granular material having a structure in which magnetic particles such as Fe, Co, FeCo, and CoNiPt are dispersed in a non-magnetic film made of iron-rare earth or SiO2 or BN may be used.
Further, the magnetic layer may be of any of an in-plane type and a vertical type.

The protective layer 5 is a 10 nm-thick hydrogenated carbon (H: 30 at%) film. The protective layer plays a role of corrosion resistance and wear resistance of the magnetic layer. As the protective layer, in addition to the above-mentioned hydrogenated carbon, carbon, nitrogenated carbon, hydrogenated nitrogenated carbon, fluorinated carbon, Cr, S
iO2 and the like.

The lubricating layer 6 is a liquid lubricating film made of perfluoropolyether having a thickness of 1 nm. The lubricating layer plays a role of wear resistance. As the lubricating layer, in addition to the above-described perfluoropolyether, a fluorocarbon-based liquid lubricant or a lubricant composed of an alkali metal salt of sulfonic acid can be used. If the protective layer 5 has a function as a solid lubricant, the lubricating layer 6 can be omitted.

Next, a method of manufacturing the magnetic disk of the above-described embodiment and a method of manufacturing a glass substrate used for the magnetic disk will be described. Manufacturing Process of Glass Substrate for Magnetic Disk (1) Roughing Process First, a glass substrate made of aluminosilicate glass cut into a disk shape having a diameter of 66 mmφ and a thickness of 3 mm from a sheet glass formed by a down-draw method using a grinding wheel,
Grinding with a relatively coarse diamond wheel, diameter 66
It was molded to a diameter of 1.5 mm and a thickness of 1.5 mm.

In this case, in place of the down-draw method, a sheet glass cut out from a sheet glass formed by a float method and processed in the same manner as described above,
A disk-shaped glass body may be obtained by direct pressing using a lower mold and a body mold.

As the aluminosilicate glass, SiO2: 63.5% by weight, Al2 O3: 14.2
Wt%, Na2 O: 10.4 wt%, Li2 O: 5.4
Wt%, ZrO2: 6.0 wt%, Sb2O3: 0.4
% By weight, glass for chemical strengthening of As2 O3: 0.1% by weight.

Next, both surfaces of the glass substrate were ground one by one with a diamond grindstone having a finer grain size than the grindstone. The load at this time was about 100 kg. As a result, the surface roughness of both main surfaces of the glass substrate is set to Rmax of 10
Finished to about μm.

Next, a hole was made in the center of the glass substrate using a cylindrical grindstone, and the outer peripheral end surface was also ground to a diameter of 65 mmφ. Then, the outer peripheral end surface and the inner peripheral surface were subjected to predetermined chamfering. . At this time, the surface roughness of the end surface (side surface and chamfered portion) of the glass substrate was about 4 μm in Rmax.

(2) End Mirror Finishing Process Next, the surface roughness of the end surface portion (angular portion, side surface, and chamfered portion) of the glass substrate is 1 μm in Rmax and 0 in Ra while rotating the glass substrate by brush polishing. 0.3 μm
Polished to a degree. This end-face mirror finishing step is effective for preventing sub-film defects caused by the generation of dust from the glass substrate end face generated during the transfer of the glass substrate, the cleaning step, and the like, which adhere to the main surface of the glass substrate. The surface of the glass substrate that had been subjected to the end surface mirror finishing was washed with water.

(3) Sanding (Lapping Step) Next, the glass substrate was sanded. This sanding step aims at improving dimensional accuracy and shape accuracy.
The sanding step was performed using a lapping apparatus, and was performed twice while changing the abrasive grain size to # 400 and # 1000. Specifically, first, using alumina abrasive grains having a grain size of # 400, setting the load L to about 100 kg, and rotating the internal rotation gear and the external rotation gear, the two main surfaces of the glass substrate housed in the carrier are brought into contact with each other. Accuracy 0-1 μm, surface roughness (Rma
x) Lapping was performed to about 6 μm.

Next, lapping was performed by changing the particle size of the alumina abrasive grains to # 1000, and the surface roughness (Rmax) was 2 μm.
m. After finishing the sanding process,
Washing was carried out by sequentially immersing in a washing tank of a neutral detergent and water.

(4) First Polishing Step Next, a first polishing step was performed. This first polishing step is for the purpose of removing scratches and distortions remaining in the above sanding step, and was performed using a polishing apparatus. Specifically, the first polishing step was performed under the following polishing conditions using a hard polisher (cerium pad LP66: manufactured by Speed Fam) as the polisher.

Polishing liquid: cerium oxide (particle size: 1.3 μm)
(Free abrasive) + water Load: 80-100 g / cm2 Polishing time: 30-50 minutes Removal amount: 35-45 μm Lower platen rotation speed: 40 rpm Upper platen rotation speed: 35 rpm Inner gear rotation speed: 14 rpm Outer gear rotation speed ： 29rpm

The glass substrate having been subjected to the above polishing step is sequentially immersed in each of washing tanks of a neutral detergent, pure water, pure water, IPA (isopropyl alcohol) and IPA (steam drying).
Washed. In addition, ultrasonic waves were applied to each cleaning tank. This cleaning step can be omitted when the polishing liquid in the next second polishing step is used together. Also, the first
The hard polisher used in the polishing process is not particularly limited,
It can be appropriately selected depending on the target surface roughness, the end shape of the substrate, and the like.

(5) Second Polishing Step (Final Polishing) Next, using the polishing apparatus used in the first polishing step, the polisher is changed from a hard polisher to a soft polisher (Kanebo N751).
A second polishing step was performed instead of 9). Polishing conditions are
Polishing liquid: Cerium oxide (particle diameter 0.8 μm) (free abrasive grains)
+ Water, load: 80 to 100 g / cm2, polishing time: 9 to
It was the same as the first polishing step, except that the removal amount was 3 to 5 μm for 15 minutes. The surface roughness of the main surface of the glass substrate obtained by the second polishing step was measured by AFM (atomic force microscope).
max = 3.8 nm. Here, the soft polisher used in the second polishing step is not particularly limited. However, in order to form the projections formed through the subsequent surface treatment step into a convex shape, it is preferable to use a polisher having relatively low hardness, and the polisher has a hardness (Asker C) of 60 or less, more preferably. Is preferably 55 or less.

(6) Surface Treatment Step (Cleaning Step) The glass substrate after the second polishing step is subjected to silicic acid (concentration: 0.35%, temperature: 45 ° C., immersion time: 150).
sec), silica hydrofluoric acid (concentration: 0.28%, temperature: 45)
The substrate was sequentially immersed in each treatment (washing) tank at 200 ° C. and immersion time: 200 sec) to perform surface treatment (washing). In addition, ultrasonic waves were applied to each treatment (washing) tank.

The glass substrate after the surface treatment step is
Immerse in each washing tank of neutral detergent, pure water, pure water, IPA (isopropyl alcohol), IPA (steam drying) sequentially,
Washed. In addition, ultrasonic waves were applied to each cleaning tank other than the IPA vapor tank used in the step of IPA (steam drying).

(7) Chemical Strengthening Step Next, the glass substrate after the above-mentioned grinding, polishing, surface treatment (washing) and washing steps was chemically strengthened. For chemical strengthening,
A chemically strengthened salt prepared by mixing potassium nitrate (60%) and sodium nitrate (40%) is prepared.
The substrate was heated to 300 ° C., and the cleaned glass substrate preheated to 300 ° C. was immersed for about 3 hours. In this immersion, in order to chemically strengthen the entire surface of the glass substrate, the immersion was performed in a state where a plurality of glass substrates were housed in a holder so as to be held at end faces.

As described above, by immersing in the chemically strengthened salt, lithium ions and sodium ions in the surface layer of the glass substrate are replaced by sodium ions and potassium ions in the chemically strengthened salt, respectively, and the glass substrate is strengthened. The thickness of the compressive stress layer formed on the surface layer of the glass substrate was about 100 to 200 μm. The glass substrate that had been chemically strengthened was immersed in a water bath at 20 ° C., rapidly cooled, and maintained for about 10 minutes.

(8) Washing Step The glass substrate after the rapid cooling was immersed in sulfuric acid heated to about 40 ° C., and washed while applying ultrasonic waves. Inspection of the surface of the glass substrate thus obtained,
No foreign body was found.

The surface roughness of the main surface of the glass substrate after the above-mentioned cleaning step was measured by AFM.
m, Rmax = 14.1, B.I. H. (2.5) = 6.02n
m, B. H. (5.0) = 4.33 nm, Rmax / Ra
= 10.8, B.I. H. (2.5) /Rmax=0.43,
B. H. (5.0) /Rmax=0.31.

When the surface condition of the main surface of the glass substrate after the final polishing and the surface condition of the main surface of the glass substrate after the above-mentioned cleaning step were observed by AFM, it was found that a convex portion was present at the locus of the free abrasive grains in the final polishing step. It was confirmed that a portion was formed. In particular, it is considered that a portion having a relatively high residual strain in the residual stress distribution formed on the glass main surface by the free abrasive grains is formed as a convex portion.

Manufacturing Process of Magnetic Disk The glass substrate for a magnetic disk obtained through the above-described processes is subjected to heat treatment of the glass substrate, formation of a seed layer, formation of an underlayer, formation of a magnetic layer, and formation of a protective layer. Each step of film formation was continuously performed using an in-line type sputtering apparatus.

This in-line type sputtering apparatus comprises:
Although not shown, the first chamber in which the substrate heating heater is installed, the NiAl target (N
i: 50 at%, Al: 50 at%), CrMo target (Cr: 94 at%, Mo: 6 at%) and CoC
rPtTa target (Co: 75 at%, Cr: 17
At%, Pt: 5 at%, and Ta: 3 at%) are sequentially provided, and a third chamber in which a carbon target is provided is provided.

Then, when the glass substrate is introduced into the first chamber via the load lock chamber, the glass substrate is sequentially conveyed in each of the chambers by a predetermined conveying device at a predetermined constant speed. Film formation and processing are performed under the conditions described above. That is, in the first chamber,
A process of heating the glass substrate at 350 ° C. for 2 minutes is performed. In the second chamber, the seed layer 2 having a thickness of 40
nm NiAl film, 25 nm thick CrM as the underlayer 3
An O film and a CoCrPtTa film having a thickness of 27 nm, which is the magnetic layer 4, are formed. In the third chamber, a 10 nm-thick hydrogenated carbon film serving as the protective layer 5 is sequentially formed.

The sputtering conditions in the second and third chambers are such that the sputtering pressure is 2 mTorr in the second chamber and 3 mTo in the third chamber.
rr, the sputtering atmosphere in the second chamber is an inert gas of argon, and the sputtering atmosphere in the third chamber is a mixed gas in which 8% hydrogen is mixed with an inert gas of argon. Further, each sputtering power was set to 2 kW in the second chamber and 3 kW in the third chamber.

Next, the substrate having undergone the steps up to the formation of the protective layer is taken out of the above-mentioned in-line type sputtering apparatus, and a perfluoropolyether liquid lubricant is applied to the surface of the protective layer by a dipping method. A magnetic disk according to Example 1 was obtained by forming a lubricating layer of 1 nm.

Table 2 in FIG. 6 shows the evaluation results of the electromagnetic conversion characteristics and CSS durability characteristics of the obtained magnetic disk. When the magnetic characteristics and recording / reproducing characteristics of the obtained magnetic disk were measured, good results were obtained in which the coercive force was 2300 Oe and the S / N ratio was 20 dB. The coercive force was measured by cutting out a sample of 8 mmφ from the manufactured magnetic disk, applying a magnetic field in the direction of the film surface, and measuring the maximum externally applied magnetic field of 10 kOe using a vibrating sample magnetometer.

The recording and reproducing characteristics (S / N ratio) were measured as follows. That is, using the obtained magnetic disk, an MR (magnetoresistive) head having a magnetic head flying height of 0.055 μm, a relative speed between the MR head and the magnetic disk of 9.6 m / s and a linear recording density of 163 kfc
The recording / reproducing output at 1 (linear recording density of 163,000 bits per inch) was measured. In addition, medium noise during signal recording and reproduction was measured by a spectrum analyzer with a carrier frequency of 23 MHz and a measurement band of 26 MHz, and the S / N ratio was calculated. MR used for this measurement
The head has a track width of 3.1 / 2.4 μm and a magnetic head gap length of 0.35 /
0.28 μm.

Further, in a 100,000 times CSS durability test using a 30% head slider with a rotation speed of 4000 rpm and a load of 3 g under a normal temperature and normal humidity atmosphere, the adsorption phenomenon between the magnetic disk and the magnetic head. A magnetic disk having high CSS durability was obtained without occurrence of head crash.

The coefficient of static friction between the magnetic disk and the magnetic head was measured by a strain gauge and found to be 0.6. Next, when a glide height test using an AE sensor was performed, it was confirmed that contact did not occur between the head and the medium up to a head flying height of 1.0 μ inch. That is, the glide height of this disk was 1.0 μ inch. From the above results, a magnetic disk which was recorded and reproduced with a glide height of 1.2 μ inch or less and satisfied high electromagnetic conversion characteristics and high CSS durability characteristics was obtained.

Comparative Example 1 Next, a glass substrate was manufactured by changing the polishing conditions and the surface treatment time with silica hydrofluoric acid, and the surface roughness of the glass substrate was evaluated by tallying. Similarly, a magnetic disk was prepared, and the coefficient of static friction, glide height (μ inch), CS
The S durability characteristics are shown as Comparative Example 1 in Table 2 of FIG. The evaluation conditions of the tally step measured at this time were a scanning distance of 250 μm and a stylus pressure of 7 mg.

As in Comparative Example 1, when the surface of the glass substrate for a magnetic disk was evaluated by the tally step (although the surface roughness was within the range of the surface roughness specified in the present invention), the glide height was reduced. The result was 2 μ inches or more, and the variation was large. This is because the stylus-type measuring method such as tally step cannot capture fine irregularities because the radius of curvature of the needle is large, so that a magnetic disk that can satisfy a glide height of 1.2 μ inch or less can be obtained. This indicates that it is difficult to control the surface state.

Therefore, in order to control the surface state of the magnetic disk which can satisfy the glide height of 1.2 μ inch or less, the surface roughness is evaluated by an atomic force microscope (AFM) capable of observing a finer surface state. I knew it had to be done. The surface roughness of the glass substrate shown below is measured by AFM.

(Examples 2 to 17, Comparative Examples 2 to 9)
A magnetic disk was prepared in the same manner as in Example 1, except that the polishing conditions (particle size of free abrasive grains) and the surface treatment time with silica hydrofluoric acid were changed to change the surface roughness of the glass substrate.
These are Examples 2 to 17 and Comparative Examples 2 to 9 and, in each case, the surface roughness Rma of the main surface of the glass substrate.
x (nm), Ra (nm), Rmax / Ra, B.I. H.
(2.5) / Rmax, B.R. H. (5.0) / Rmax, coefficient of static friction, glide height (μ inch), and CSS durability characteristics are shown in Table 2 in FIG.

The coercive force and S / N ratio of the magnetic disks in Examples 2 to 17 and Comparative Examples 2 to 9 were measured.
Good values of 200 Oe or more and 18 dB or more were shown. In Comparative Example 4, the surface roughness R of the main surface of the glass substrate
When the value of max was less than 5.0 nm, the magnetic head was attracted to the magnetic disk due to the mirror state. In Comparative Example 2, the glide height exceeded 1.2 μm because the surface roughness Rmax of the main surface of the glass substrate exceeded 25.0 nm.

In Comparative Example 6, since the surface roughness Ra of the main surface of the glass substrate was less than 0.2 nm, the coefficient of friction became 3 or more, and a head crash occurred.
In Comparative Example 3, the glide height was 1.2 due to the surface roughness Ra of the main surface of the glass substrate exceeding 2.5 nm.
exceeded μ inch. In Comparative Example 5, Rmax / Ra is 8
When the value was less than 3, the head crash occurred because the coefficient of friction became 3 or more. B. H. (2.5)
/ Rmax and B.I. H. (5.0) / Rmax is larger than 0.5 and 0.45, respectively.

In Comparative Examples 7 and 8, Rmax / R
When a exceeded 20, the CSS durability was lowered and a head crash occurred. B. H. (2.5) / R
max and B.I. H. (5.0) / Rmax is smaller than 0.1. In Comparative Example 8, when the particle size of the free abrasive grains was less than 0.3 μm, the surface durability was reduced, and the CSS durability was deteriorated. In Comparative Example 9,
When the particle size of the free abrasive grains exceeded 3.0 μm, the surface roughness increased, and the glide height exceeded 1.2 μ inch.

From the above results, it was found that recording / reproduction was performed at a flying height of 1.2 μ inch or less, high electromagnetic conversion characteristics, and high CSS.
In order to obtain a magnetic disk that satisfies the durability characteristics, the surface roughness of the glass substrate for a magnetic disk should be within the range specified in the present invention, and during manufacturing, in final polishing before surface treatment with silica hydrofluoric acid. It was found that the particle size of the free abrasive grains had to be within a predetermined range.

Optimization of the concentration of silicofluoric acid (Example 1, Examples 18 to 21, Comparative Examples 10 to 12) Next, the concentration of silicic acid was changed in the surface treatment with silicic acid after final polishing. Magnetic disks were manufactured in the same manner as in Example 1, and these were designated as Example 1, Examples 24 to 27, and Comparative Examples 18 to 20. In each case, the surface roughness Rmax (n
m), Ra (nm), Rmax / Ra, static friction coefficient,
The glide yield is summarized in Table 3 in FIG. Here, the glide yield was defined as a magnetic disk which was hit when a magnetic disk manufactured under each condition was prepared and each was inspected at a flying height of 1.2 μ inch by a glide head. Further, the coercive force and S / N ratio of the magnetic disks in Examples 18 to 21 and Comparative Examples 10 to 12 were measured, and showed good values of 2200 Oe or more and 18 dB or more.

In Comparative Example 11, the concentration of silica hydrofluoric acid was 1.0
Since the content exceeded the weight percent, the controllability of etching was poor and the variation in surface roughness became large, so that a reproducible product could not be produced. In Comparative Example 10, a sufficient etching effect was not obtained because the concentration of silicofluoric acid was less than 0.15% by weight, so that the surface roughness of the main surface of the glass substrate became a mirror surface, and the magnetic head was adsorbed. Was.
In Comparative Example 12, the concentration of silicic acid in the first treatment was 0.15.
Although it was set to less than% by weight, an appropriate roughness was obtained by increasing the concentration of the second treatment, but the dispersion was large and the yield was low.

From the above results, it is possible to control the surface roughness with high accuracy by setting the concentration of silicic acid to a predetermined range (0.15 to 3.0% by weight), and to obtain a stable magnetic disk. A magnetic disk that can be supplied, has a glide height of 1.2 μ inch or less, and satisfies high electromagnetic conversion characteristics and high CSS durability characteristics was obtained.

Optimization of Surface Roughness of Glass Substrate After Final Polishing (Example 1, Examples 22 to 27, Comparative Examples 13 to 15) Next, the polishing conditions were changed to change the surface of the glass substrate after final polishing. Except that the roughness was changed, magnetic disks were manufactured in the same manner as in Example 1, and these were used in Examples 1 and 2.
2 to 27 and Comparative Examples 13 to 15, in each case, the surface roughness Rmax (n
m), Ra (nm), Rmax / Ra, static friction coefficient,
The glide height (μ inch) and CSS durability characteristics are summarized in Table 4 in FIG. Example 1, Examples 22 and 2
7, the coercive force of the magnetic disk in Comparative Examples 13 to 15,
The S / N ratio was measured and found to be good values of 2000 Oe or more and 18 dB or more.

In Comparative Example 13, the surface roughness of the glass substrate main surface after final polishing was less than 1.0 nm in Rmax,
When the Ra was less than 0.1 nm, the roughness was small even after the silica hydrofluoric acid treatment, and the friction coefficient exceeded 3. Comparative Example 1
In No. 4, since the surface roughness of the main surface of the glass substrate after final polishing exceeded 1.0 nm in Ra, Ra after silica hydrofluoric acid treatment became 2.5 nm or more. occured. In Comparative Example 15,
Since Rmax and Ra are large, the glide height is 1.
It was 2 μ inches or more.

From the above results, by making the surface roughness of the glass substrate after final polishing a predetermined roughness, it is possible to suppress the dispersion of the projections on the surface of the glass substrate finally obtained. A magnetic disk having a glide height of less than inches and satisfying high electromagnetic conversion characteristics and high CSS durability characteristics was obtained.

Glass Type of Glass Substrate (Example 28, Comparative Examples 16 to 17) Next, the glass substrate was changed to aluminosilicate glass (Example 28), quartz glass (Comparative Example 16), and soda lime glass (Comparative Example 17). Instead, a magnetic disk was manufactured in the same manner as in Example 1 except that the polishing conditions and the surface treatment conditions using silica hydrofluoric acid were appropriately changed in order to make these glass substrate surfaces have a predetermined surface roughness. The composition of the aluminosilicate glass used in Example 28 was 64.0% by weight of SiO2, 16.0% by weight of Al2 O3, 9.0% by weight of Na2O, and 7.0% by weight of Li2O. , ZrO2: 4.0% by weight, the composition of soda lime glass used in Comparative Example 17 above was SiO2: 72.5% by weight, Na2O: 15.2%.
0% by weight, Al2 O3: 1.0% by weight, CaO: 9.0
Glass of 2.5% by weight and 2.5% by weight of MgO was used.

As a result, in Example 28, the surface roughness was R
a = 1.2 nm, Rmax = 11.0 nm, the coefficient of friction was 1.9, and the CSS durability was good. However, the surface roughness of Comparative Examples 16 and 17 was larger than that of Examples 1-28. It has a different shape, the coefficient of static friction is 3 or more, and CS
Good results were not obtained in S durability characteristics. As described above, the reason why the projections are formed differently depending on the glass type of glass is considered from the results of the above-described example and Comparative Examples 16 and 17, and the glass substrate surface is contained in water in the polishing step using free abrasive grains. It is considered that an exchange reaction between H + and alkali ions (Na +, Li +) contained in the glass has occurred. It seems that OH is attached to Si or Al forming the glass network by the exchange reaction. A hydrated layer that is easily etched is formed. In the hydrated layer, the stress distribution due to the difference in the stress applied by the free abrasive grains (the part where the stress is large, the etching rate decreases,
It is considered that a portion having a small stress has a high etching rate), and unevenness is formed due to the difference in the etching rate. The ease with which the hydration layer is formed is related to the formation of projections and depressions (projections), which is considered to be due to the difference in glass type of glass. In Comparative Example 1 described above, since no alkali metal oxide was contained in the glass, no hydration layer was formed and no irregularities were formed. As a result of examining the reason why no irregularities were formed on the glass in Comparative Example 2, it was considered that the alkaline earth oxides (CaO, MgO) contained in the glass of Comparative Example 2 were involved in the formation of the irregularities. The effect of alkaline earth oxides was studied. The glasses shown in Table 5 of FIG. 9 are seven types of glass materials having different alkaline earth oxide contents. This glass material was treated with silica hydrofluoric acid in the same manner as in Example 1 to produce a glass substrate. In addition, the surface of the glass substrate before the hydrofluoric acid treatment and the surface of the glass substrate after the hydrofluoric acid treatment were observed with an atomic force microscope (AFM). As a result, in the case of a glass substrate containing no TiO2 (glasses A to D), a glass substrate containing at least 2 mol% (1.6 wt% or more) of alkaline earth oxides (MgO, CaO) (glass C, D) In (2), it was confirmed that the roughness of the surface as shown in the above example was not remarkable, and it was difficult to form a convex portion. On the other hand, a glass substrate containing TiO2 (E ~
In the case of G), alkaline earth oxides (MgO, CaO)
Total content of 3 mol% or more (2.4 wt% or more)
It was confirmed that the glass (glass G) contained had no noticeable surface roughness as shown in the above-described examples, and it was difficult to form convex portions. From the above results, the glass composition for forming the projections by the production method of the present invention contains at least an alkali metal oxide in order to form a hydrated layer on the glass substrate surface during the polishing step using free abrasive grains. And hinders the exchange reaction of alkali ions for forming the above-mentioned hydrated layer. It was found that the content of the alkaline earth oxide was desirably less than 3 mol% (less than 2.4 wt%). More preferably, the total content of the alkaline earth oxides is desirably less than 2 mol% (less than 1.6 wt%).

If the etching rate of the glass substrate by the silica hydrofluoric acid treatment is too high, it is difficult to control the irregularities (particularly the shape of the projections). SiO2 content (in the case of glass containing TiO2, SiO2 + Ti
It is desirable that the total amount of O2) be 65 mol% or more. Therefore, as the glass used in the production method of the present invention, any glass that satisfies the above conditions may be used.Moreover, in order to improve the mechanical strength of the glass substrate, it is necessary to consider a point that enables chemical strengthening. , Its composition ratio is
SiO2: 58 to 75% by weight, Al2 O3: 5 to 23% by weight, Li2 O: 3 to 10% by weight, Na2 O: 4 to 13%
What is necessary is just to consist of the material which contains a weight% as a main component, Furthermore, desirably it is an alkaline-earth metal (oxide).
It was found that it was desirable to use a glass containing no. In particular, the aluminosilicate glass as defined in claim 13 is preferable under the above-mentioned polishing conditions and surface treatment conditions using silicic acid. However, even for a glass substrate other than the glass defined in claims 12 to 13, the polishing conditions and the surface treatment conditions are selected to obtain the surface roughness conditions defined in claims 1 to 3. As a result, a magnetic disk having a glide height of 1.2 μ inch or less and satisfying high electromagnetic conversion characteristics and high CSS durability characteristics can be obtained. Claims 1-3
Even if it is a very smooth glass substrate having no surface roughness as defined in the above, fine projections are formed on the main surface of the glass substrate, and the surface roughness according to claims 1 to 3, the present invention The same effect can be obtained.

In the above description, the surface roughness range of the glass substrate for a magnetic recording medium for obtaining the desired glide height, friction coefficient, and CSS durability has been mainly described. Investigate how the surface treatment conditions (silicon hydrofluoric acid concentration, immersion time in silica hydrofluoric acid, silica hydrofluoric acid treatment temperature) affect the surface roughness of the glass substrate for magnetic recording media. The control method will be described. FIGS. 10 and 11 are graphs showing the relationship between the immersion time in silica hydrofluoric acid and Rmax and the relationship between the immersion time in silica hydrofluoric acid and Ra when the particle size of the abrasive grains is changed.
The concentration and temperature of the silicic acid at this time are constant, and are 0.28% by weight and 45 ° C., respectively. As shown in FIG. 10, Rmax does not depend on the particle size of the abrasive grains, and has a correlation with the immersion time in hydrofluoric acid and Rmax can be controlled by adjusting the immersion time in hydrofluoric acid. Is shown. Also, as shown in FIG.
Depending on the immersion time in silica hydrofluoric acid (for example,
80 sec) There is a correlation between the particle size of the abrasive grains and Ra, indicating that Ra can be controlled by adjusting the particle size of the abrasive grains. Further, the concentration of silicic acid and the temperature of silicic acid treatment are related to the etching rate. As the concentration and temperature increase, the etching rate increases and the surface roughness Rmax tends to increase. Actually, when a glass substrate for a magnetic recording medium is manufactured by the manufacturing method of the present invention, since the surface roughness changes greatly due to the fluctuation of the concentration of the hydrofluoric acid and the temperature of the hydrofluoric acid, the silicon fluoride is always maintained at a constant etching rate. It is necessary to monitor the acid concentration and the hydrofluoric acid treatment temperature. In particular, the concentration of silicofluoric acid has a correlation with the conductivity, and the monitoring and control of the conductivity can accurately control the etching rate. In the above-described embodiments, the magnetic recording medium mainly used in the CSS system has been described. However, a typical glass substrate for a magnetic recording medium used in the load / unload system and an example in which the magnetic recording medium is manufactured Is shown below. The particle size of the abrasive grains and the surface treatment conditions (silicon hydrofluoric acid concentration, silica hydrofluoric acid treatment temperature, and immersion time in silica hydrofluoric acid) in Example 1 were appropriately adjusted, and Rmax = 4.3 nm and Ra =
A glass substrate for a magnetic recording medium having a surface roughness of 0.46 nm and Rmax / Ra = 9.3 was produced. A seed layer, an underlayer, a magnetic layer, a protective layer, and a lubricating layer were formed on the obtained glass substrate in the same manner as in Example 1 to obtain a magnetic recording medium.
The obtained magnetic recording medium had good coercive force and S / N ratio, good glide characteristics, no head crash, etc., and also good flying characteristics. As described above, the present invention has been described with reference to the preferred embodiments. However, the present invention is not necessarily limited to the above embodiments. For example, although the surface treatment with silicic acid in the above embodiment was performed in two stages, it may be performed in one surface treatment step or in three or more surface treatment steps.

Further, the glass substrate of the present invention uses glass for chemical strengthening, and the chemical strengthening step is performed after the surface treatment with silica hydrofluoric acid. However, the surface treatment with silica hydrofluoric acid may be performed after the chemical strengthening treatment. In that case, the glass substrate is polished with free abrasive grains, and immediately after the glass substrate surface is chemically strengthened, if the above-described surface treatment with silicic acid is performed, by chemical strengthening, the glass substrate surface is formed by free abrasive grains. Since the residual strain is buried in the stress of chemical strengthening, the surface roughness cannot be controlled, which is not preferable.However, chemical strengthening process → polishing treatment with free abrasive grains → chemical strengthening treatment such as surface treatment with silica hydrofluoric acid The same result as described above can be obtained by inserting a polishing treatment step using free abrasive grains between the step and the surface treatment step using silica hydrofluoric acid (immediately after the surface treatment using silica hydrofluoric acid). Further, the disk manufactured by the present invention can be used not only in the CSS system but also in the zone texture system and the load / unload system.

[0119]

As has been described in detail above, the present invention is to make the surface roughness of the main surface of a glass substrate for a magnetic recording medium a specific state when measured by an atomic force microscope (AFM). Thereby, it is possible to obtain a magnetic recording medium glass substrate and a magnetic recording medium that constitute a magnetic recording medium having a glide height of 1.2 μ inches or less, high electromagnetic conversion characteristics, and high CSS durability characteristics, Further, it is possible to further chemically treat a glass substrate having a predetermined surface roughness state when the surface roughness of the main surface is measured by an atomic force microscope with silica hydrofluoric acid or the like to the above-described specific surface roughness state. Is what it is. Further, the glass substrate is set so that the ratio of Ra, Rmax, Rmax / Ra specified by an atomic force microscope (AFM) or the bearing height of the isosurface having a specific value of the bearing ratio to Rmax is in a specific range. By controlling the surface roughness of the main surface, it is possible to obtain a glass substrate for a magnetic recording medium used for a magnetic disk or the like which satisfies high electromagnetic conversion characteristics and high CSS durability characteristics.

[Brief description of the drawings]

FIG. 1 is a view showing a photograph taken by an atomic force microscope (AFM) of a main surface of a glass substrate for a magnetic recording medium according to the present invention.

FIG. 2 is a diagram showing a measurement curve of surface irregularities on a specific straight line on the surface shown in FIG. 1;

FIG. 3 is a diagram showing a bearing curve of the surface unevenness shown in FIG. 1;

FIG. 4 shows a magnetic disk with a known density of protrusions measured by AFM. H. It is a figure which shows Table 1 which put together the result which computed / Rmax.

FIG. 5 is a schematic sectional view showing a configuration of a magnetic disk according to the first embodiment of the present invention.

FIG. 6 is a table showing a summary of evaluation results of electromagnetic conversion characteristics and CSS durability characteristics of the magnetic disks of Examples 1 to 17 and Comparative Examples 1 to 9.

FIG. 7 is a diagram showing Table 3 in which the evaluation results of the electromagnetic conversion characteristics and CSS durability of the magnetic disks of Examples 1, 18 to 21 and Comparative Examples 10 to 12 are summarized.

FIG. 8 is a diagram showing Table 3 in which the evaluation results of the electromagnetic conversion characteristics and CSS durability of the magnetic disks of Examples 1, 22 to 27 and Comparative Examples 13 to 15 are summarized.

FIG. 9 is a diagram showing Table 5 in which the compositions of various glasses constituting the glass substrate are summarized.

FIG. 10 is a graph showing the relationship between the immersion time in Teffluoric acid and Rmax when the particle size of the abrasive grains is changed.

FIG. 11 is a graph showing the relationship between the immersion time in silica hydrofluoric acid and Ra when the grain size of the abrasive grains is changed.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Glass substrate, 2 ... Seed layer, 3 ... Underlayer, 4 ... Magnetic layer, 5 ... Protective layer, 6 ... Lubricating layer

Claims (18)

[Claims] At least the surface roughness of the main surface, when measured by an atomic force microscope (AFM), is Ra = 0.2-2.
5 nm, Rmax = 3 to 25 nm, Rmax / Ra = 3
35. A glass substrate for a magnetic recording medium, comprising: 2. The glass substrate for a magnetic recording medium according to claim 1, wherein a plane parallel to an imaginary main surface when the main surface of the glass substrate for a magnetic recording medium is assumed to be completely flat. When the unevenness formed on the main surface of the magnetic recording medium glass substrate is cut by the contour surface, the value of the total area of the virtual main surface with respect to the sum of the areas of the cut surface Is defined as a bearing ratio, and a contour surface at which the bearing ratio is 50% is defined as a reference surface, and a distance from the reference surface to a contour surface having each bearing ratio is defined as a bearing height. The bearing height on the contour surface, which is 2.5% of the bearing ratio, is defined as B.
H. (2.5) The bearing height on the contour surface, which is 5.0% of the bearing ratio, H. (5.0), B. H. (2.5) /Rmax=0.1-0.5, or
B. H. (5.0) A glass substrate for a magnetic recording medium, wherein /Rmax=0.1 to 0.45. 3. The surface roughness of at least the main surface, when measured by an atomic force microscope (AFM), is Rmax = 3 to 25.
nm and B.I. H. (2.5) /Rmax=0.1
~ 0.5 or B.I. H. (5.0) /Rmax=0.1-0.
45. A glass substrate for a magnetic recording medium, which is 45. (However, BH (2.5) and BH (5.0) are as defined in claim 2) 4. The glass substrate for a magnetic recording medium according to claim 1, wherein said glass substrate contains at least an alkali metal oxide. 5. The glass substrate for a magnetic recording medium according to claim 1, wherein said glass substrate contains at least an alkali metal oxide and less than 3 mol% of an alkaline earth oxide. Glass substrate for a magnetic recording medium. 6. The glass substrate for a magnetic recording medium according to claim 1, wherein the glass substrate is used for a magnetic disk having a glide height of 1.2 μ inch or less. . 7. A magnetic recording medium, wherein at least a magnetic layer is formed on the main surface of the glass substrate for a magnetic recording medium according to claim 1. 8. A glass substrate having a main surface having a surface roughness Ra of 0.1 to 1.0 nm as measured by an atomic force microscope (AFM), wherein at least a main surface of the glass substrate is provided. The surface roughness is Ra =
0.2-2.5 nm, Rmax = 3-25 nm, Rma
A method for producing a glass substrate for a magnetic recording medium, comprising performing a chemical surface treatment so that x / Ra = 3 to 35. 9. A glass substrate whose main surface has a surface roughness Ra of 0.1 to 1.0 nm as measured by an atomic force microscope (AFM) is prepared. A method for producing a glass substrate for a magnetic recording medium, comprising performing a surface treatment with silicic acid. 10. The method for producing a glass substrate for a magnetic recording medium according to claim 8, wherein at least the main surface of the glass substrate is treated with 0.1% before the chemical surface treatment or the surface treatment with silica hydrofluoric acid. 3 ~
A method for producing a glass substrate for a magnetic recording medium, comprising polishing using an abrasive containing free abrasive grains having a particle diameter of 3.0 μm. 11. The method of manufacturing a glass substrate for a magnetic recording medium according to claim 10, wherein the chemical surface treatment or the surface treatment with silicic acid is performed.
In the polishing step of the glass substrate, the process is performed such that a portion having a relatively high residual strain becomes a convex portion in a residual stress distribution generated at a position of a polishing locus by the free abrasive grains. A method for manufacturing a glass substrate for a magnetic recording medium. 12. The method of manufacturing a glass substrate for a magnetic recording medium according to claim 9, wherein the concentration of said hydrofluoric acid is 0.15 to 3.0% by weight. A method for manufacturing a glass substrate for a recording medium. 13. The method of manufacturing a glass substrate for a magnetic recording medium according to claim 8, wherein the glass constituting the glass substrate contains at least an alkali metal oxide and an alkaline earth oxide. A method for producing a glass substrate for a magnetic recording medium, wherein the content of the alkaline earth oxide is less than 3 mol%. 14. The method for manufacturing a glass substrate for a magnetic recording medium according to claim 13, wherein the glass constituting the glass base material has a SiO 2
A glass substrate for a magnetic recording medium, comprising 75% by weight, 5 to 23% by weight of Al2 O3, 3 to 10% by weight of Li2 O, and 4 to 13% by weight of Na2 O. Manufacturing method. 15. The method for manufacturing a glass substrate for a magnetic recording medium according to claim 14, wherein the glass constituting the glass base material is made of SiO2 of 62 to 60.
75% by weight, 5 to 15% by weight of Al2 O3, 4 to 10% by weight of Li2 O, 4 to 12% by weight of Na2 O, ZrO2
5.5 to 15% by weight as a main component, the weight ratio of Na2 O / ZrO2 is 0.5 to 2.0, and A
A method of manufacturing a glass substrate for a magnetic recording medium, wherein the glass has a weight ratio of l2O3 / ZrO2 of 0.4 to 2.5. 16. The method for manufacturing a glass substrate for a magnetic recording medium according to claim 8, wherein a chemical strengthening treatment is performed after said chemical surface treatment or said surface treatment with silicic acid. Of manufacturing a magnetic disk glass substrate. 17. A method for manufacturing a glass substrate for a magnetic recording medium according to claim 8, wherein at least a magnetic layer is formed on a main surface of the glass substrate for a magnetic recording medium. Of manufacturing a magnetic recording medium. 18. The surface state of a glass substrate for a magnetic recording medium for improving the flying characteristics of a magnetic head for each type of magnetic head, as measured by an atomic force microscope (AFM).
The surface of the glass substrate for a magnetic recording medium is surface-treated under various surface treatment conditions, and the surface state after the treatment is determined by an atomic force microscope (A).
Ra, Rma obtained when measured by FM)
A magnetic processing method comprising: determining surface treatment conditions when each of x and Rmax / Ra falls within the above specific range; and performing a surface treatment on the surface of the glass substrate for a magnetic recording medium according to the determined surface treatment conditions. A method for manufacturing a glass substrate for a recording medium.