JP2001243617A - Friction coefficient management method based on surface roughness, substrate for information recording medium, information recording medium and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To highly precisely design or manage a friction coefficient based on surface roughness in an information recording medium substrate having the surface roughness of Rmax 15 nm or lower, and an information recording medium. SOLUTION: The information recording medium substrate has the surface roughness of Rmax 15 nm or lower. For example, a bearing value (offset bearing area value: OBA%) from a hearing height (rear peak height) corresponding to a bearing area 0.5% to a 3 nm depth (slicing level) is 90% or lower, and a friction coefficient based on surface roughness is 3 or lower.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for managing a coefficient of friction based on surface roughness, a substrate for an information recording medium, an information recording medium and a method of manufacturing the same.

[0002]

2. Description of the Related Art As an information recording medium, there is a magnetic recording medium mounted on a hard disk drive (HDD). The remarkable dramatic increase in the recording capacity of HDDs in recent years has been realized, in part, by the reduction in the gap between the head and the medium (the flying height of the head) during recording and reproduction (reduction in glide). The reduction of the head-medium gap has been realized by efforts to smooth the medium surface, but the smoothing of the medium surface, on the other hand, causes an adsorption problem between the head and the medium. Therefore, the design of the medium surface always suffers from a trade-off between low glide and avoidance of head suction. Precise surface design is required to solve the conflicting problem of smoothing the media surface required for low glide and avoiding the tendency of adsorption (= tendency to increase the coefficient of friction) due to smoothing It is.

Conventionally, AFM has been used for managing the shape of the medium surface from the viewpoint that process feedback is easy.
Surface roughness parameters such as Rmax and Ra by (atomic force microscope), normalized roughness Ra / Rmax, and the like have been used.

[0004]

However, when the relationship between Rmax, Ra or Ra / Rmax measured by AFM and the friction coefficient was examined, it was found that the low glide region (about 10 nm or less) required more precise surface design. It has been found that such a surface management technique is too insensitive. 1 and 2 show the substrate surface roughness measured by AFM (Rmax (FIG. 1), Ra (FIG. 2)).
And the coefficient of friction, but with the same Rmax
(For example, even if Rmax is about 7.5 nm, the friction coefficient has a width of about 0.7 to 2.2, so that Rmax
It is not possible to manage the coefficient of friction with parameters such as Ra and Ra.

On the other hand, there has been proposed a method of managing the friction coefficient by correlating the bearing area (bearing ratio) with the friction coefficient. Specifically, in a magnetic recording medium having a texture formed on the medium surface, the texture (irregularity) is formed so that the bearing area at a depth of 20 nm from the surface top is 20% or less, and the friction coefficient is specified to be small. (Japanese Patent Laid-Open No. 5-18)
No. 9756). Note that the bearing area refers to a ratio of an area that appears when the unevenness in the measurement area is cut at an arbitrary level surface (horizontal plane) to the measurement area,
It can be measured using an AFM (atomic force microscope) or the like. However, this technique mainly focuses on a magnetic recording medium in which the surface of an aluminum alloy substrate having a NiP film formed on the surface is polished with free abrasive grains and textured, and a bearing at a depth of 20 nm from the top of the surface. Since the area is used as a parameter (that is, a magnetic recording medium having a rough surface (20 nm or more) is used), a magnetic recording medium having a surface roughness of Rmax 15 nm or less is quite useful as a friction coefficient management method. There is no problem. Note that this technique is derived from experiments and is not derived based on the theory of a true contact area or the like described later. Furthermore, for example, if the method of forming the texture is different, the total number of projections, the shape of the projections (the radius of curvature of the projections, the horizontal cross-sectional shape, the height of the projections) are different, and even if the Rmax and Ra are the same, the friction due to the medium surface is different. Since the coefficients are different, it can be said that in this case, the above technique is not useful at all as a method for managing the friction coefficient of the medium surface.

The present invention has been made under the above-mentioned background, and provides a novel surface management method capable of obtaining a precise surface design even in a low glide region of about 10 nm or less. It is an object of the present invention to provide an information recording medium substrate (magnetic recording medium substrate), an information recording medium (magnetic recording medium), a method of manufacturing the same, etc.

[0007]

The present inventors have conducted intensive studies on the frictional force acting on the magnetic head and found the following. The frictional force acting on the magnetic head usually
Since there is a lubricant and moisture in the air, it can be expressed by the following equation (1). F = μN + F1 + F2 + F3 + (1) In the above equation (1), F is a friction force, μ is a static friction coefficient, N is a normal force, F1 is a meniscus force by a lubricant,
F2 is the meniscus force of water, and F3 is the adhesion force of other substances (such as organic contaminants). Head (or pad for reducing the contact area with the magnetic disk)
At the contact surface between the pad (bud) of the slider with (bad) and the medium surface with a certain surface roughness, the true contact area is smaller than the apparent contact area because the medium surface has irregularities. Very small. When the load of the head is applied,
The pressure concentrated on the top of the projection crushes the top of the projection, increasing the true contact area and increasing the frictional force. However, there is no change in the apparent contact area. At the true contact surface, adhesion occurs between the surfaces that are in contact with each other. Therefore, as the true contact area increases, a large force (force to cut off a frictional force or the like) is required to separate (shear) the adhesion surface. . From the above, it can be said that μN∝the true contact area. Therefore, from the viewpoint of the surface design, it is presumed that if a shape parameter representing the true contact area between the magnetic head and the medium is extracted, it becomes a theoretically sensitive index for friction.

When the surface roughness obtained by precision polishing of the glass substrate surface is less than Rmax 15 nm, the true contact area between the magnetic head and the medium is proportional to the total number of protrusions that the head can contact (FIG. 9). When the relationship between the total number of projections at a predetermined depth from the maximum projection height in the 5 μm square AFM image to 4 nm and the friction coefficient was examined, the friction coefficient was dependent on the total number of projections (projection density) at the predetermined depth (proportionality). ) However, since it takes a certain amount of time to calculate the protrusion density from the AFM data, it is difficult to say that process feedback is easy, and it is not a parameter suitable for a process monitor. Therefore, it was examined whether the projection density at a predetermined depth cannot be directly represented by any AFM measurement value. Specifically, for example, a 5 μm square (5 μm
(m × 5 μm) The relationship between the bearing area at a depth from the maximum projection height (Rmax) to 4 nm in the AFM image and the total number of projections at the same depth was examined. It was found that there was a proportional relationship with the projection density at a given depth. Further, when the relationship between the bearing area at a depth from the maximum protrusion height (Rmax) in the 5 μm square AFM image to 4 nm and the friction coefficient was examined, the relationship shown in FIG. 10 was obtained. It was found that there was a correlation between the bearing area and the friction coefficient. The bearing area at this predetermined depth position is A
This parameter is easily obtained as an FM measurement result, is easy for process feedback, and is suitable for a process monitor. As described above, as a shape parameter representing the true contact area, for example, the maximum protrusion height (Rmax)
It has been found that the friction coefficient can be controlled with respect to a magnetic recording medium or the like having a surface roughness of Rmax 15 nm or less by using a bearing area near a depth of 4 nm from the surface as a parameter.

[0009] However, when the bearing area is measured by the AFM, the AFM itself has measurement variations. Also, the presence of abnormal projections (irregular points) that do not affect the glide height and do not affect the friction coefficient, such as dust, may cause AFM measurement variations. Due to these variations, Rmax measured by AFM does not represent the true peak height. These variations are usually about 1 to 2 nm, and have a great influence on a magnetic recording medium having a surface roughness (texture) of Rmax 15 nm or less. In particular, Rm
For a magnetic recording medium having a surface roughness (texture) of ax10 nm or less, the influence of the variation of 1-2 nm is extremely large. For example, if the maximum protrusion height is out of order by 1 to 2 nm, the slice level is also out of order by 1 to 2 nm, and it may not be possible to manage the friction coefficient in the bearing area corresponding to this slice level. Even if it can be managed, the friction coefficient of the magnetic recording medium managed in this bearing area varies greatly because the slice level is incorrect (not optimal), and is insufficient as a friction coefficient management method. I found it.

As a result of further research, AFM
When the bearing curve is repeatedly measured according to the formula, the value of the bearing area at which the measured value of the bearing height starts to fluctuate rapidly near the maximum protrusion height (BA = 0%) is obtained. It has been found that the problem of AFM measurement variation can be solved by using various AFM measurement values excluding data up to the value of the bearing area where the measurement value of the AFM starts to vary rapidly. For example, when a bearing curve is repeatedly measured by AFM (atomic force microscope) on a surface having a surface roughness of about Rmax 15 nm or less,
In the vicinity of the maximum protrusion height (BA = 0%), a bearing area value at which the measured value of the bearing height starts to fluctuate rapidly is determined (0.5% in FIG. 7), and the corresponding bearing height (true peak) is obtained. Height) is determined from the bearing curve (FIG. 8). Bearing area at a predetermined depth (3 nm in FIG. 8) from this true peak, in other words, the bearing area when the slice level is offset (subtracted) (offset bearing area: OBA%)
And the coefficient of friction of the medium surface is examined by changing the predetermined depth. From this correlation, the predetermined depth at which the corresponding amount of change in the bearing area becomes larger with respect to the amount of change in the coefficient of friction. (Predetermined slice level).
By managing the friction coefficient based on the correlation (for example, FIG. 5) between the bearing area value (offset bearing area value) and the friction coefficient at the predetermined slice level, the friction coefficient based on the surface roughness is accurately managed. I found what I could do. In this way, by adopting OBA% as an index having high sensitivity to friction and employing this OBA% as a process monitor index, the friction coefficient based on the surface roughness can be managed with high accuracy. Also, in the surface design of the medium, the correlation between OBA% and the coefficient of friction between OBA% and the forming conditions for forming the surface state of the medium (such as the total number of protrusions and curvature) is determined in advance. Through the correlation, the friction coefficient based on the surface roughness can be designed with high precision, and a magnetic recording medium having a desired friction coefficient can be obtained by selecting the above-mentioned forming conditions.

The present invention has the following configuration.

(Structure 1) An information recording medium substrate having a surface roughness of Rmax 15 nm or less, wherein the surface of the substrate has a bearing height (true) corresponding to a bearing area value of 0.2% to 1.0%. From 0.5 to 5
An information recording medium substrate, wherein a bearing area value (offset bearing area value) at a depth of nm (predetermined slice level) is 90% or less.

(Structure 2) An information recording medium substrate having a surface roughness of Rmax 15 nm or less, wherein the surface of the substrate has a bearing height (true) corresponding to a bearing area value of 0.2% to 1.0%. A bearing area value (offset bearing area value) of 90% or less when a slice level is a depth corresponding to 20 to 45% of Rmax from the peak height of the information recording medium.

(Structure 3) The information recording medium substrate comprises:
3. The information recording medium substrate according to Configuration 1 or 2, wherein the substrate is a glass substrate having a surface subjected to precision polishing and / or etching treatment.

(Constitution 4) Rmax 15 nm on the medium surface
An information recording medium having the following surface roughness, wherein the medium surface of the information recording medium has a bearing area value of 0.2%
The bearing area value (offset bearing area value) at a depth of 0.5 to 5 nm (predetermined slice level) from a bearing height (true peak height) corresponding to １．０1.0% is 90% or less. Information recording medium.

(Arrangement 5) Rmax 15 nm on the medium surface
An information recording medium having the following surface roughness, wherein the medium surface of the information recording medium has a bearing area value of 0.2%
When the slice level is a depth corresponding to 20 to 45% of Rmax from the bearing height (true peak height) corresponding to ~ 1.0%, the bearing area value (offset bearing area value) is 90% or less. An information recording medium, characterized in that:

(Structure 6) Structure 4 or 5, wherein the friction coefficient based on the surface roughness of the medium surface is 3 or less.
An information recording medium according to claim 1.

(Structure 7) Structure 4 characterized in that the correlation between the coefficient of friction and the offset bearing area in the information recording medium in which various lubricants are formed is examined, and a lubricant that reduces the frictional force due to the lubricant is employed. 7. The information recording medium according to any one of items 6 to 6.

(Structure 8) The lubricant is PFPE (pe
rfluoro alkyl polyether) to be classified, includes an ether bond in the main chain, - (it OCF ₂ F ₂₎ has an m (OCF ₂₎ n-linear structure, and a lubricant having a hydroxyl group as an end group The information recording medium according to configuration 7, wherein:

(Structure 9) A step of immersing a glass substrate in a heated chemical strengthening treatment liquid, and exchanging ions of a surface layer of the glass substrate with ions in the chemical strengthening treatment liquid to chemically strengthen the glass substrate; A step of treating the surface of the glass substrate pulled up from the liquid with a treatment liquid containing silicic acid,
A method for producing a glass substrate for an information recording medium, comprising:

(Structure 10) A step of polishing the surface of a glass substrate, immersing the glass substrate in a heated chemical strengthening treatment liquid, and ion-exchanging ions in the surface layer of the glass substrate with ions in the chemical strengthening treatment liquid. Chemically strengthening the
The method for producing a glass substrate for an information recording medium having a step of controlling the surface of the glass substrate to a desired surface roughness by a chemical treatment before the step of chemically strengthening, and the glass substrate pulled up from the chemical strengthening treatment liquid Treating the surface of the substrate with a treatment liquid containing silicic acid.

(Structure 11) The chemical treatment includes sulfuric acid,
The method for manufacturing a glass substrate for an information recording medium according to Configuration 10, wherein the glass substrate is treated with a treatment liquid containing at least one acid selected from phosphoric acid, nitric acid, hydrofluoric acid, and silicic hydrofluoric acid, or an alkali.

(Structure 12) The concentration of the silicic hydrofluoric acid is
12. The method for producing a glass substrate for an information recording medium according to any one of Configurations 9 to 11, wherein the content is 0.01 to 10% by weight.

(Structure 13) A method for manufacturing an information recording medium, comprising forming at least a recording layer on the surface of the glass substrate for information recording medium obtained by Structures 9 to 12.

(Arrangement 14) This is a method for managing a friction coefficient based on the surface roughness of an information recording medium having a surface roughness of Rmax 15 nm or less. The bearing curve was repeatedly measured by an AFM (atomic force microscope). In the case, near the maximum protrusion height (BA = 0%),
A bearing area value at which the measured value of the bearing height starts to fluctuate rapidly is determined, a bearing height (true peak height) corresponding to the bearing area value is determined from a bearing curve, and a predetermined depth is determined from the true peak height. The bearing area and the friction coefficient based on the surface roughness are examined by changing the predetermined depth, and from the correlation, the change amount of the friction coefficient is compared with the change amount of the bearing area corresponding to the change amount of the friction coefficient. Is determined at a predetermined depth (predetermined slice level), and a bearing area value (offset bearing area value) at the predetermined slice level is obtained.
A friction coefficient management method based on surface roughness, wherein the friction coefficient is managed based on the surface roughness by using the method.

(Structure 15) Rmax 15n is formed on the medium surface.
A method for managing a friction coefficient based on the surface roughness of an information recording medium having a surface roughness of not more than m, and a bearing area at a depth of 0.5 to 7 nm (slice level) from a maximum height (Rmax) measured by AFM. A friction coefficient management method based on surface roughness, wherein the friction coefficient is managed based on the surface roughness by using the method.

(Structure 16) Rmax 15n is formed on the medium surface.
This is a method of managing the coefficient of friction based on the surface roughness of an information recording medium having a surface roughness of not more than m, and the maximum height (Rmax) measured by AFM is 20 to 40 of Rmax.
A friction coefficient management method based on surface roughness, wherein a friction coefficient is managed based on surface roughness using a bearing area when a depth corresponding to% is set to a slice level.

(Structure 17) A method of manufacturing an information recording medium for manufacturing an information recording medium having a desired medium surface based on the friction coefficient management method based on the surface roughness of Structures 14 to 16.

(Structure 18) In a method of manufacturing an information recording medium substrate for reflecting a surface of an information recording medium substrate to a desired medium surface by reflecting the surface of the information recording medium surface, Structure 1
An information recording medium substrate manufacturing method for manufacturing an information recording medium substrate having a desired substrate surface based on a friction coefficient management method based on surface roughness of Nos. 4 to 16.

(Structure 19) This is a method for managing the surface condition of a substrate for an information recording medium having a surface roughness of Rmax 15 nm or less. When a bearing curve is repeatedly measured by an AFM (atomic force microscope), In the vicinity of the maximum protrusion height (BA = 0%), the bearing area value at which the measured value of the bearing height starts to fluctuate rapidly is determined. From BA = 0%, the bearing area value at which the measured value of the bearing height starts to fluctuate rapidly. A surface state management method characterized by using various AFM measurement values excluding the above data.

(Structure 20) A method for manufacturing an information recording medium substrate for manufacturing an information recording medium substrate having a desired substrate surface based on the surface state management method of Structure 19.

(Structure 21) This is a method of managing the surface condition of the surface of an information recording medium having a surface roughness of Rmax 15 nm or less. When a bearing curve is repeatedly measured by an AFM (atomic force microscope), the maximum protrusion is obtained. In the vicinity of the height (BA = 0%), a bearing area value at which the measured value of the bearing height starts to fluctuate rapidly is determined.
A surface state management method using various AFM measurement values excluding data from A = 0% to a bearing area value at which a measurement value of a bearing height starts to fluctuate rapidly.

(Structure 22) A method for manufacturing an information recording medium for manufacturing an information recording medium having a desired medium surface based on the surface state management technique of Structure 21.

[0034]

According to the configuration 1, the bearing area value at which the measured value of the bearing height starts to fluctuate rapidly from an experiment on the surface of the information recording medium substrate (magnetic recording medium substrate) by the method of the configuration 14 described later. 0.2% to 1.0
%, And a depth of 0.5 to 5 nm from the true peak height is determined as a slice level, and the bearing area value (offset bearing area value: OBA%) at this slice level is defined as 90% or less. When an information recording medium (magnetic recording medium) is used, an information recording medium (magnetic recording medium) having a small friction coefficient (usually 3 or less) based on the surface roughness can be obtained.

Further, as in the configuration 2, the depth of the slice level in the configuration 1 is defined as the depth corresponding to 20 to 45% of Rmax, and the bearing area value (offset bearing area value: By defining OBA% to be 90% or less, an information recording medium (magnetic recording medium) having a small friction coefficient (usually 3 or less) based on the surface roughness when the information recording medium (magnetic recording medium) is used. can get. In particular, Configuration 1,
No. 2 is suitable for a substrate having an information recording medium substrate (magnetic recording medium substrate) having a surface roughness of Rmax 10 nm or less. In the case of an information recording medium substrate (magnetic recording medium substrate) with Rmax = about 10 to 11 nm, for example,
Slice level = 4 nm (36-40% of Rmax),
OBA% = 70% or less is preferable. Rmax = 7-8n
For information recording medium substrates (magnetic recording medium substrates) of about m, for example, the slice level = 3 nm (Rmax
38-43%), OBA% = 90% or less (in the case of a substrate for a CSS type magnetic recording medium, preferably 40% ± 20%)
% (20 to 60%), preferably 70% ± 20% (50 to 50%) in the case of a load / unload type magnetic recording medium substrate.
90%)). In the case of an information recording medium substrate (magnetic recording medium substrate) with Rmax = about 5 to 6 nm,
For example, slice level = 1.5 to 2 nm (25 to 40% of Rmax), OBA% = 80% or less (in the case of a load / unload type magnetic recording medium substrate, preferably 6%).
0% ± 20% (40-80%)). Further, in the case of an information recording medium substrate (magnetic recording medium substrate) having an ultra-smooth substrate surface having an Rmax of 3 nm or less, for example, the slice level is 0.5 to 1.3 nm (Rmax of 20 to 1.3 nm).
43%), OBA% = 90% or less (in the case of a load / unload type magnetic recording medium substrate, preferably 70% ±
20% (50-90%) is preferred. The bearing area value at which the measured value of the bearing height starts to fluctuate rapidly may be about 0.5%.
The value may be 1.0%, preferably 0.3 to 0.7%, and more preferably 0.4 to 0.6%.

According to the third aspect, the information recording medium substrate (magnetic recording medium substrate) is a glass substrate whose surface has been precisely polished and / or etched. Substrate (magnetic recording medium substrate) can be obtained reliably and easily. As a specific manufacturing method of the etching process, there are means of Configurations 9 to 12 described later.

According to the constitutions 4 and 5, similarly to the constitutions 1 and 2, the information recording medium (magnetic recording medium) having a surface roughness of Rmax 15 nm or less on the medium surface, and the surface roughness (texture) of the medium surface ), The information recording medium (magnetic recording medium) having a small friction coefficient (usually 3 or less) can be obtained. In particular, Configurations 4 and 5 are suitable for an information recording medium (magnetic recording medium) having a surface roughness Rmax of 10 nm or less on the information recording medium surface (magnetic recording medium surface). In the case of an information recording medium (magnetic recording medium) having a surface roughness Rmax of about 10 to 11 nm on the medium surface, for example, slice level = 4 nm (36 to 40% of Rmax), OBA
% = 70% or less is preferable. For an information recording medium (magnetic recording medium) with Rmax = about 7 to 8 nm, for example,
Slice level = 3 nm (38 to 43% of Rmax),
OBA% = 90% or less (preferably 40% ± 20% (20 to 60%) in the case of a CSS type magnetic recording medium, preferably 7% in the case of a load / unload type magnetic recording medium)
0% ± 20% (50-90%)). Rmax
= 5 to 6 nm, the slice level = 1.5 to 2 nm (R
max 25% to 40%), OBA% = 80% or less (in the case of a load / unload type magnetic recording medium, preferably,
60% ± 20% (40-80%)) is preferable. Also,
In the case of an information recording medium (magnetic recording medium) having an ultra-smooth medium surface with an Rmax of 3 nm or less, for example, a slice level = 0.5 to 1.3 nm (20 to 43% of Rmax),
OBA% = 90% or less (in the case of a load / unload type magnetic recording medium, preferably 70% ± 20% (50 to 9%)
0%). The bearing area value at which the measured value of the bearing height starts to fluctuate rapidly may be about 0.5%, and more specifically, 0.2 to 1.0%, preferably 0.3 to 0.7%. More preferably 0.4 to 0.6
Any value within the range of% may be used. In order to obtain the medium surface of Structures 4 to 6, the surface state of the medium surface is controlled by the substrate surface as in Structures 1 to 3, and an underlayer,
A method of obtaining a desired medium surface by forming a magnetic layer, a protective layer, a lubricating layer, and the like, and a method of controlling a surface state of any layer formed on a substrate to obtain a desired medium surface are exemplified. . Methods for controlling the surface state include mechanical treatment, chemical treatment, growth of crystal grains by sputtering, and optical treatment such as laser light. By using the glass substrate for an information recording medium (magnetic recording medium) whose surface has been precisely polished and / or etched as shown in the above-mentioned constitution 3, the information recording medium (magnetic recording medium) according to constitutions 4 to 6 can be obtained. Is preferable because it can be obtained reliably and easily. Also, since there is no need to provide a layer for controlling the surface condition of the medium surface between the magnetic layer and the magnetic head, the spacing (flying height) between the magnetic recording medium and the magnetic head is reduced, and high recording density reproduction is achieved. This is preferable because it becomes possible.

According to the sixth aspect, by defining the friction coefficient based on the surface roughness (texture) of the medium surface to be 3 or less, the information recording medium (magnetic recording medium) having the friction coefficient based on the surface roughness being 3 or less. ) Is reliably obtained. Preferably, the coefficient of friction is 2 or less, more preferably 1.5 or less.

According to the configuration 7, the correlation between the friction coefficient and the offset bearing area in the information recording medium (magnetic recording medium) in which various lubricants are formed is examined, and the lubricant which reduces the frictional force by the lubricant is selected. be able to. It should be noted that lubrication that reduces the frictional force due to the lubricant can also be performed by performing the same evaluation on the lubricant formed on the surface using the friction coefficient management method based on the surface roughness described in Configurations 14 to 16. It goes without saying that the agent can be selected.

According to the constitution 8, PFPE (perfluoroal
kyl polyether), which contains an ether bond in the main chain, has a-(OCF2F2) m (OCF2) n-linear structure, and has a hydroxyl group as a terminal group. The frictional force can be reliably reduced.

Structures 9 to 14 are specific methods for obtaining the information recording medium substrate (magnetic recording medium substrate) of structures 1 to 3 and the information recording medium (magnetic recording medium) of structures 4 to 8 above. is there. However, the information recording medium substrate (magnetic recording medium substrate) of Configurations 1 to 3 and the information recording medium (magnetic recording medium) of Configurations 4 to 8 are not limited by the following manufacturing method. According to the ninth aspect, a step of immersing the glass substrate in the heated chemical strengthening treatment liquid and ion-exchanging ions on the surface layer of the glass substrate with ions in the chemical strengthening treatment liquid to chemically strengthen the glass substrate; Treating the surface of the glass substrate pulled up from the surface with a treatment liquid containing silicic acid, thereby suppressing variations in surface roughness,
BA% can be controlled accurately. The inventors of the present invention have measured variations of the AFM itself when the bearing area is measured by the AFM (measurement variations due to abnormal protrusions which do not affect the glide height and do not affect the friction coefficient). With regard to the chemical strengthened glass substrate, the cause was investigated to find that abnormal protrusions and the like, which cause measurement variations, are often caused in the chemical strengthening process, or the surface roughness is reduced by the chemical strengthening process after precision polishing. Increase was found to be the cause. Then, it was considered that OBA% can be controlled accurately by suppressing the cause of the measurement variation. By performing the hydrofluoric acid treatment as the treatment after the chemical strengthening treatment, abnormal protrusions and the like that cause the above-mentioned measurement variation are removed, and the OBA% can be strictly controlled. Further, as in the structure 10, it is preferable that the surface of the glass substrate is controlled to a desired surface roughness by a chemical treatment before the step of chemically strengthening. Chemical treatment (excluding silicic acid treatment) to control the surface roughness to the desired level after chemical strengthening treatment results in a chemically strengthened layer (compressive stress layer, tensile stress layer)
, Which is not preferable because it causes a change in the flatness of the substrate. As in Configuration 11, the chemical treatment is performed with a treatment liquid containing at least one acid selected from sulfuric acid, phosphoric acid, nitric acid, hydrofluoric acid, and silicofluoric acid, or an alkali. The concentration of these acids and alkalis, the processing temperature and the processing time are appropriately adjusted in accordance with the surface condition of the substrate to be obtained. As in Configuration 12, the concentration of silicic acid in the silicic acid treatment after the chemical strengthening treatment is:
0.01 to 10% by weight is preferred. If the content is less than 0.01% by weight, abnormal projections and the like that cause the AFM measurement variation may not be reliably removed.
If the content is more than 10% by weight, the surface of the glass substrate is etched, and the surface condition of the substrate surface controlled by the chemical treatment before the chemical strengthening treatment is changed, or the surface roughness is undesirably increased. Preferably, 0.05 to 7% by weight,
More preferably, 0.1 to 5% by weight is preferable from the viewpoint of controllability. Further, by forming at least a recording layer (magnetic layer) on the surface of the glass substrate for an information recording medium (magnetic recording medium) obtained by Configurations 9 to 12, as in Configuration 13, a desired friction coefficient can be obtained. An information recording medium (magnetic recording medium) having the above is obtained. The material of the magnetic layer in the present invention is not particularly limited. A known magnetic layer material can be used. In addition to the magnetic layer, an underlayer that controls the crystal orientation of the magnetic layer to improve the magnetic properties, a protective layer that improves the corrosion resistance and mechanical durability of the magnetic recording medium, a lubricating layer that adjusts the friction coefficient, and an underlayer Alternatively, a seed layer for controlling the crystal grain size and the grain size distribution of the magnetic layer can be formed. these,
Known materials can also be used for the seed layer, the underlayer, the protective layer, and the lubricating layer.

According to the structure 14, since the correlation between the offset bearing area and the friction coefficient (for example, FIG. 5) is proportional and has a high sensitivity, the information recording medium is used by using the offset bearing area. (Magnetic recording medium) The friction coefficient based on the surface roughness of the surface can be designed or managed with high accuracy. Particularly, in the configuration 14, when managing the friction coefficient based on the medium surface roughness of the information recording medium (magnetic recording medium), the information recording medium substrate (magnetic recording medium substrate) and the information recording medium (magnetic recording medium) It can be applied to surface roughness management, and the surface roughness of those surfaces is Rmax 15 nm
The following is further suitable for those having an Rmax of 10 nm or less. According to Configuration 15, the maximum protrusion height (Rma
x) using the bearing area at 0.5-7 nm depth (slice level) from and according to configuration 16,
From the maximum protrusion height (Rmax), 20 to 45 of Rmax
% By using the bearing area when the depth corresponding to the slice level is taken as the slice level, the friction coefficient based on the surface roughness is controlled by controlling the friction coefficient based on the surface roughness. Coefficients can be roughly designed or managed.

According to the seventeenth aspect, by manufacturing an information recording medium (magnetic recording medium) having a desired medium surface based on the friction coefficient management method based on the surface roughness of the above-mentioned fourteenth to sixteenth aspects, An information recording medium (magnetic recording medium) having a friction coefficient of As a method for obtaining an information recording medium (magnetic recording medium) having a desired medium surface,
A method in which the surface condition of the medium surface is controlled by the substrate surface, and a base layer, a recording layer (magnetic layer), a protective layer, a lubricating layer, etc. are formed on the substrate surface to obtain a desired medium surface, or formed on the substrate. A method of controlling the surface state of any one of the layers to obtain a desired medium surface. In particular, the spacing (flying height) between the information recording medium (magnetic recording medium) and the magnetic head
It is preferable to control the substrate surface in order to reduce the recording density and enable high recording density reproduction.
It is preferable that the present invention be applied to a method for manufacturing a substrate for an information recording medium (a substrate for a magnetic recording medium) having a desired substrate surface based on a friction coefficient management method based on the surface roughness of 4 to 16.

According to the constitutions 19 and 21, as a method of managing the surface state of the information recording medium substrate (magnetic recording medium substrate) or the information recording medium (magnetic recording medium), the bearing height is measured from BA = 0%. The problem of AFM measurement variation can be solved by using various AFM measurement values excluding data up to the bearing area value at which the value starts to vary rapidly. For example, when OBA% is used, it is hardly affected by AFM measurement variations, and the friction coefficient based on the surface roughness can be designed or managed with high accuracy. Note that the configurations 19 and 21
The various AFM measurement values mentioned above include Rmax, Ra, Ra / Rm in addition to OBA% (offset bearing area).
ax, BA% (bearing area) and the like. Further, for example, data in which the measured values vary from the AFM measurement data is excluded, and the data after the exclusion is used to determine the bearing curve, Rmax, Ra, Ra / Rmax, BA%
And the like, the influence of AFM measurement variations can be excluded, and accurate data can be obtained. These operations are performed by AFM
It can be easily performed by setting in the measuring device. As in Configuration 20, by applying to a method for manufacturing a substrate for an information recording medium (magnetic recording medium substrate) having a desired substrate surface based on the surface state management technique of Configuration 19, a desired friction coefficient can be obtained. An information recording medium substrate (magnetic recording medium substrate) for obtaining an information recording medium (magnetic recording medium) having the same is obtained. In addition, as in Configuration 22, Configuration 2
By applying the present invention to a method for manufacturing an information recording medium (magnetic recording medium) having a desired medium surface based on the surface state management method, an information recording medium (magnetic recording medium) having a desired friction coefficient can be obtained. Can be

[0045]

BEST MODE FOR CARRYING OUT THE INVENTION A description will now be given of a magnetic recording medium substrate and a method of manufacturing a magnetic recording medium from a medium design of a magnetic recording medium mounted on a hard disk drive according to the present invention. FIG. 11 is a diagram for explaining a method for manufacturing a magnetic recording medium substrate and a magnetic recording medium from a medium design of the magnetic recording medium. FIG. 12 is a diagram for explaining a magnetic recording medium substrate and a method for manufacturing the magnetic recording medium.
In order to finally obtain the magnetic recording medium, as shown in FIG. 11, the medium designing step (steps a to e), the magnetic recording medium substrate manufacturing step (step f), the magnetic recording medium manufacturing step (step g).

The medium (magnetic recording medium surface) design step includes the following steps: a. Surface roughness (Rmax) of the medium (magnetic recording medium) surface
Determining the relationship between the magnetic head and the flying height (glide height) of the magnetic head at which the magnetic head starts to contact the medium surface; b. Determining a surface roughness (Rmax) of the medium surface to achieve a desired glide height from the relationship obtained in the step a; c. Determining an allowable range of a coefficient of friction on a medium surface according to a driving torque of a spindle motor of the hard disk drive; d. Determining a correlation between OBA% (offset bearing area) and the coefficient of friction; e. Determining an OBA% for obtaining a desired coefficient of friction from the correlation obtained in the step d.

Note that OBA% (offset bearing area) is a parameter for designing the medium surface and is a feature of the present invention, and is obtained by the following steps (steps d-1 to d-4 shown in FIG. 11). decide. The following steps are usually determined by preparing a plurality of samples (magnetic recording medium or magnetic recording medium substrate). d-1. Obtaining a relationship between Rmax and the bearing area by AFM; d-2. Determining a true peak height (a bearing value at which the measured value of the bearing height starts to fluctuate rapidly) according to the medium surface roughness; d-3. Obtaining a correlation between the depth from the true peak height obtained in the step d-2 and the bearing area, and determining a slice level at which the amount of change in the bearing area becomes large; d-4. Determining a bearing area value (OBA%: offset bearing area) at the slice level determined in the step d-3. In addition, the coefficient of friction and the surface roughness of the medium surface in the above-described medium design process are often set to a certain extent by hard disk drive manufacturers in relation to the recording density. The media manufacturer may omit step c above.

Since the medium surface has the OBA% determined by the above medium design process, the substrate surface has a desired OBA
% Of a magnetic recording medium substrate. The manufacturing process of the chemically strengthened glass substrate for a magnetic recording medium of the present invention will be described below. The manufacturing process of chemically strengthened glass substrates for magnetic recording media
As shown in steps f-1 to f-8 in FIG. Examining the relationship between the manufacturing conditions of the chemically strengthened glass substrate for magnetic recording media and OBA% (omitted after determining the manufacturing conditions); f-2. A substrate forming step of forming a disk-shaped glass substrate; f-3. A shape processing step of making a center hole in the glass substrate and grinding the inner and outer peripheries of the disc-shaped substrate; f-4. A grinding step of lapping the main surface of the glass substrate; f-5. A polishing step of polishing the main surface of the glass substrate (an end face polishing step of polishing an end face of the glass substrate may be performed, if necessary); and f-6. A chemical strengthening step of strengthening the surface of the glass substrate; f-7. A process of treating the glass substrate after the chemical strengthening process with silicic acid; f-8. Inspecting and packing the glass substrate. Note that a cleaning step of cleaning the glass substrate is introduced between each step as needed. The manufacturing conditions in the step f-1 include, for example, polishing conditions (abrasive type, abrasive particle size, pressure, time, polishing pad type, etc.) for polishing the substrate surface, and control of the substrate surface roughness. Chemical treatment conditions (chemical solution type, concentration, temperature, time), chemical strengthening treatment conditions for glass substrate chemical strengthening treatment (molten salt species, heating temperature, time),
Silica hydrofluoric acid treatment conditions after chemical strengthening (concentration, temperature, time)
And the like. Since various conditions are determined in advance by experiments on these relationships, the f-1 step may be omitted in the actual manufacturing process of the glass substrate. Also,
In the steps f-2 and f-3, a donut-shaped substrate can be formed by direct pressing, and the steps f-2 and f-3 can be performed in the same step. The method of manufacturing a chemically strengthened glass substrate according to the present invention is characterized in that the method includes a step of treating the surface of the glass substrate pulled up from the chemical strengthening treatment liquid with a treatment liquid containing silicic acid. By treating the surface of the glass substrate after the chemical strengthening treatment with a treatment liquid containing silica hydrofluoric acid, variation in surface roughness can be suppressed, and OBA% can be accurately controlled.
The silica hydrofluoric acid treatment can effectively remove the cause of the measurement variation of the AFM itself (abnormal projections that do not affect the glide height and do not affect the friction coefficient), and strictly remove the OBA%. Can be controlled. FIG. 13 shows the Rm of the glass substrate for a magnetic recording medium obtained by the method for producing a glass substrate for a magnetic recording medium of the present invention.
FIG. 14 shows the relationship between ax and OBA% 3 nm (silicon hydrofluoric acid treatment conditions, concentration: 1.0% by weight, treatment time: 100 seconds, 128 substrates), and FIG. 14 shows the surface of the glass substrate after the chemical strengthening treatment. Rmax and OBA% 3 of the magnetic recording medium glass substrate obtained by sulfuric acid treatment (sulfuric acid treatment condition, concentration: 10% by weight, treatment condition: 100 seconds, 128 substrates)
It is a figure which shows the relationship with nm. 13 and 14, the glass substrates for magnetic recording media were manufactured such that the OBA% 3 nm was in the range of 20 to 40%.
As can be seen from a comparison between FIGS. 13 and 14, in the case of FIG. 13, it is found that the OBA% is approximately in the range of 3 nm = 20 to 40%, and is distributed collectively near Rmax = 8 nm. . On the other hand, in the case of FIG.
3nm is not within the range of 20-40%,
It can be seen that Rmax is also widely distributed from about 5 nm to about 16 nm. Thus, it can be seen that by subjecting the surface of the glass substrate after the chemical strengthening treatment to the hydrofluoric acid treatment, the cause of the measurement variation of the AFM itself can be effectively removed, and the OBA% can be strictly controlled.

Next, in order to obtain a magnetic recording medium, a magnetic layer or the like is formed on the glass substrate for a magnetic recording medium obtained by the above-mentioned steps, thereby producing a magnetic recording medium. A typical magnetic recording medium manufacturing process will be described below. As shown in steps g-1 to g-4 in FIG. Forming an underlayer on a glass substrate; g-2. Forming a magnetic layer on the underlayer; g-3. Forming a protective layer on the magnetic layer; g-4. Forming a lubricating layer on the protective layer. The materials of the underlayer, the magnetic layer, the protective layer, and the lubricating layer are not particularly limited. Further, a seed layer may be provided between the glass substrate and the underlayer for the purpose of controlling the crystal grain size and the particle size distribution of the underlayer and the magnetic layer. Further, an intermediate layer for controlling the crystal orientation of the magnetic layer may be provided between the underlayer and the magnetic layer. The thickness and composition of each of these layers are formed by appropriately adjusting according to the required characteristics. Hereinafter, an example of manufacturing a magnetic recording medium substrate and a magnetic recording medium according to the above steps will be described.

(Embodiment 1) Hereinafter, a 2.5-inch diameter hard disk drive (4200 rpm) and about 5 GB per medium
The following is an example of a medium design in a case where the recording capacity is required. (1) Rma specified by required glide height
x design In order to achieve the above-mentioned 5 GB recording capacity, read / write (R) is required because of the improvement of the S / N ratio and the narrowing of the track width.
/ W) The flying height of the head needs to be reduced to about 20 nm. For this reason, the glide height must be reduced to about 8 to 10 nm. This means that head-media contact must not occur even with a head flying height of only 10 nm. FIG. 3 shows the surface roughness Rmax (measured by AFM) of the medium surface and the flying height (glide height) of the magnetic head at which the magnetic head starts to contact the medium surface.
6 is a graph showing a relationship with the graph. To achieve the required glide height of 10 nm from this graph, Rm
ax must be about 8 nm or less. (2) Design of friction coefficient at Rmax specified in (1) According to (1), Rmax for achieving the required glide height was specified. Under these constraints, the friction coefficient is designed to avoid the magnetic head being attracted to the medium. The upper limit of the friction coefficient of the hard disk drive is defined by the driving torque of the spindle motor. When the friction is so large that the magnetic head cannot rotate with the driving torque, the magnetic head is attracted to the medium surface. In the model of the 4200 rpm motor in the present embodiment, the upper limit of the friction coefficient is specified to be 3 or less. By the way, as described above, OBA% for controlling the coefficient of friction is representative of the density of protrusions in a certain depth space, and therefore, is most sensitive to friction according to the defined Rmax. The slice position needs to be determined. FIG. 4 shows various mediums having an Rmax of about 8 nm defined in the above (1), and shows a bearing curve in the medium. Although the Rmax and Ra values of each medium are almost the same, the bearing curves are greatly different, and therefore the projection density and the projection shape are different, and the friction coefficient is different. In discriminating (the friction coefficients of) these media, a depth of 3 nm is set as the optimum slice level from the bearing height (true peak height) corresponding to the bearing area 0.5%. The bearing area when the slice level is offset from the maximum projection height is referred to as an offset bearing area, and is described as OBA% ＢＡ3 nm. FIG. 5 shows the population shown in FIG. 2 expressed as OBA% ＠ 3 nm. By introducing OBA% ＢＡ3 nm, R
It became possible to manage the friction coefficient, which was impossible with max, Ra, and Rmax / Ra. Above upper limit of friction coefficient <3
OBA% マ ー ジ ン
Standards management is performed at 3 nm = 40% ± 20%. Thereby, the coefficient of friction is controlled within the range of 0.5 to 2.5.

The medium surface of the magnetic recording medium has the above (1),
Rmax, OBA% ＠ 3 nm = 40% specified in (2)
In this embodiment, the surface roughness of the magnetic recording medium substrate is adjusted to Rmax, O,
BA% ＠ 3 nm = 40% ± 20%
On the substrate, an underlayer, a magnetic layer, a protective layer, and a lubricating layer were formed to produce a magnetic recording medium.

(3) Preparation of Substrate for Magnetic Recording Medium A disk-shaped glass substrate is obtained from a molten glass by direct pressing, and is subjected to shape processing (perforation and chamfering) and an end surface polishing step. A silicate glass substrate was obtained. Thereafter, a glass substrate for a magnetic recording medium was manufactured through a lapping step, a polishing step, a chemical strengthening step, and an etching treatment with silica hydrofluoric acid. The surface roughness (measured by AFM) of the glass substrate after the polishing step was as follows: Rmax = 5.72 nm, Ra
= 0.53 nm. The chemical strengthening was performed in a mixed molten salt of potassium nitrate and sodium nitrate at a processing temperature of 340 ° C. and a processing time of 2 hours. The test was performed for 100 seconds. When the surface roughness of the obtained glass substrate was measured by AFM (atomic force microscope), Rma
x = 6.92 nm, Ra = 0.79 nm, OBA% ＠ 3
nm = 41%.

(4) Production of Magnetic Recording Medium On both surfaces of the glass substrate for a magnetic recording medium obtained by the above (3), using an in-line type sputtering apparatus,
A NiAl seed layer, a CrV underlayer, a CoCrPtTa magnetic layer, and a hydrogenated carbon protective layer are sequentially formed, and a perfluoropolyether liquid lubricant (Zdol2000, manufactured by Fomblin) is formed by a dipping method to form a magnetic recording medium. Produced. The surface roughness of the obtained magnetic recording medium was determined by AFM.
(Atomic force microscope), Rmax = 7.
55 nm, Ra = 0.88 nm, OBA% ＠ 3 nm = 4
3% and a coefficient of friction of about 1.5. The TDFH of the obtained magnetic recording medium was 8.4 nm. Thus, a magnetic recording medium within the design range was obtained. In addition, 1
When the CSS durability test was performed 100,000 times, no head crash or adsorption phenomenon occurred. In addition, no head wear phenomenon was observed.

In addition, when the reproducibility of the repeated measurement (21 consecutive times) was examined in the same measurement area by AFM, the measured value of the bearing area (BA%） 4 nm) at a depth of 4 nm from Rmax was 3.6 at 3σ. While the variation was large, the measured value of OBA% ＠ 4 nm was 1.8 at 3σ, and the variation was halved. That is, O
It can be seen that BA% is less affected by AFM measurement variations.

(Embodiment 2) In Embodiment 1 described above, (1) under the constraint of Rmax defined by the glide height,
(2) designing a medium surface having a good friction coefficient; (3) preparing a magnetic recording medium substrate having the surface roughness obtained by the design; and (4) forming at least a magnetic layer on the substrate. A magnetic recording medium was manufactured. In other words, the first term (μN) on the right side, which is expressed in the above-mentioned equation of frictional force F = μN × F1 + F2 + F3 +... Here, in order to reduce the frictional force, it is also important to reduce the contribution of the second term on the right side (the meniscus force F1 due to the lubricant) that is linearly combined. Therefore, in the second embodiment, by using the above-described friction coefficient management method, the applied lubricant is optimized, and a magnetic recording medium corresponding to higher recording density is manufactured.

Specifically, PFPE (pe
The following two types of lubricants, classified as rfluoroalkyl polyethers, were studied. In both cases, the main chain contains an ether bond and has a-(OCF2F2) m (OCF2) n-straight chain structure. (A) Zdol2000: terminal group = hydroxyl group, (b) AM3000: terminal group = piperonyl group FIG. 6 shows OB for both lubricants.
FIG. 4 is a diagram illustrating a relationship between A% ＠ 3 nm and a friction coefficient. As shown in the drawing, in the combination of the magnetic head and the medium according to the present embodiment, it can be seen that (a) Zdol2000 can lower the friction coefficient (F1 is smaller). Therefore, by manufacturing a magnetic recording medium using the selected lubricant, a suitable magnetic recording medium corresponding to high recording density can be obtained.

(Examples 3 to 6) In the same manner as in Example 1, except that the chemical treatment with silica hydrofluoric acid was performed between the polishing step and the chemical strengthening step to control the surface roughness. Thus, a magnetic recording medium substrate and a magnetic recording medium were manufactured. In addition, in order to control the surface roughness, the glass substrate contains at least an alkali metal oxide and an alkaline earth oxide, and the content of the alkaline earth oxide is 3 mol%.
(Specifically, SiO ₂ : 58 to 75% by weight, Al ₂
O _3: 5 to 23 wt%, Li ₂ O: 3~10 wt%, Na
₂ O: containing 4 to 13% by weight as a main component). The conditions of the silica hydrofluoric acid treatment performed between the polishing step and the chemical strengthening step are as follows: concentration: 0.12 vol
%, Processing time: 200 seconds. Further, the treatment time of silicic acid after chemical strengthening was changed to 70 seconds (Example 3), 80 seconds (Example 4), 90 seconds (Example 5), and 100 seconds (Example 6). The change in surface roughness due to aging was investigated. As a result, as shown in FIGS. 15 to 17, as the treatment time of the silicic acid treatment after the chemical strengthening becomes longer,
It can be seen that Ra was almost constant, but Rmax decreased. From this, it is considered that by the treatment with silica hydrofluoric acid after the chemical strengthening, abnormal protrusions due to the variation in the measurement of the AFM were removed, the Rmax was reduced, and as a result, the OBA% could be controlled without variation. .

(Examples 7 to 9) Next, in Example 1, the polishing conditions and the hydrofluoric acid treatment conditions after the chemical strengthening were appropriately adjusted, whereby the substrate for the magnetic recording medium for the load / unload method, the magnetic recording A medium was prepared. The magnetic recording media of Examples 7, 8, and 9 were produced by designing the media and managing the friction coefficient so that the recording capacities became 5 GB, 10 GB, and 15 GB, respectively. Table 1 shows the surface condition (surface roughness (Rmax, OBA%), slice level, and surface level) of the magnetic recording medium substrates obtained in Examples 7 to 9.
Shows the flying characteristics.

[0059]

[Table 1]

As shown in the above table, a magnetic recording medium having good flying characteristics (head crash and fly stiction) was obtained.

Comparative Example 1 The procedure of Example 1 was repeated, except that the treatment with silicic acid after chemical strengthening was replaced with the treatment with sulfuric acid (concentration: 10% by weight, time: 100 seconds). A recording medium substrate and a magnetic recording medium were produced.
As a result, Rmax = 6.15 nm, OBA% 3 nm =
72%, and could not be within the standard range of OBA% 3 nm = 40% ± 20%. This is AFM
It is considered that the OBA% 3 nm could not be controlled because, for example, the abnormal projections, which are considered to be the cause of the measurement variation, could not be sufficiently removed. When the coefficient of friction of the obtained magnetic recording medium was measured, it was 3.5, which exceeded 3, and it was not possible to avoid the magnetic head from being attracted.

The present invention is not limited to the above embodiment.

For example, the OBA slice is not limited to 3 nm. Arbitrated as appropriate for various media.

The place where the surface roughness of the medium is created is not limited to the substrate surface. For example, a texture may be formed on an underlayer, a protective layer, or the like. The method of forming a predetermined surface roughness is also
Not only the etching method, but also a mechanical texture, a sputter texture, a laser texture, or a mixture of fine particles may be used to achieve a predetermined surface roughness. However, preferably, a texture method in which the radius of curvature and the like of each projection are substantially the same is preferable.

As a method of measuring the surface state, AFM
Instead of (atomic force microscope), an STM (scanning tunnel microscope) or a stylus type surface roughness meter can be used. However, the AFM (atomic force microscope) is superior to other measurement methods in that the surface state can be measured relatively easily, accurately, with high precision and high resolution.

As the lubricant in the second embodiment, a lubricant suitable for various media is selected. The method of forming the lubricant is not limited to the dipping method (immersion method). The lubricant may be formed by vacuum evaporation.

The present invention is not limited to the CSS type magnetic recording medium, but as shown in Examples 7 to 9, the flying stiction (Flying Stiction) in the load / unload type magnetic recording medium in which the flying height of the magnetic head is further advanced. ) It is also effective as a management method for avoidance. Further, the chemical solution used in the chemical treatment step in the surface roughness control step after the polishing step is not limited to silicic hydrofluoric acid, sulfuric acid, phosphoric acid, nitric acid, hydrofluoric acid, at least one acid selected from among hydrofluoric acid, Alternatively, the treatment may be performed with a treatment solution containing an alkali.

The size of the substrate is not limited to 2.5 inches.
It can be applied to various sizes such as inches, 3 inches, and 3.5 inches.

The present invention is not limited to a magnetic recording medium substrate and a magnetic recording medium, but also a magneto-optical recording medium substrate and a magneto-optical recording medium for recording and reproducing data using a head slider equipped with an optical pickup lens and the like. It can also be applied to the surface, and is also effective as a technique for managing those surfaces.

[0070]

According to the present invention, in an information recording medium substrate (magnetic recording medium substrate) and an information recording medium (magnetic recording medium) having a surface roughness of Rmax 15 nm or less (especially Rmax 10 nm or less), Can be designed or managed with high precision based on the friction coefficient. Further, according to the present invention, in the management of a surface state having a surface roughness of Rmax 15 nm or less (particularly, Rmax 10 nm or less), AF
The problem of the measurement variation of M can be solved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between Rmax and a coefficient of friction by AFM measurement.

FIG. 2 is a diagram showing a relationship between Ra and a coefficient of friction by AFM measurement.

FIG. 3 is a diagram illustrating a relationship between Rmax and glide height measured by AFM.

FIG. 4 is a diagram for explaining a relationship between BA% measured by AFM and a depth from a true peak height.

FIG. 5 is a diagram showing a relationship between OBA% ＠ 3 nm and a coefficient of friction.

FIG. 6: OBA% ＠ 3n in a medium coated with a lubricant
It is a figure showing the relationship between m and a coefficient of friction.

FIG. 7 is a diagram showing the relationship between BA% and bearing height near the maximum projection height.

FIG. 8 is a diagram for explaining an offset bearing area.

FIG. 9 is a diagram for explaining a contact state between a head and a projection.

FIG. 10 is a diagram showing a relationship between BA% ＠ 4 nm and a coefficient of friction.

FIG. 11 is a diagram for explaining a method for manufacturing a magnetic recording medium substrate and a magnetic recording medium, from the medium design of the magnetic recording medium.

FIG. 12 is a diagram for explaining a magnetic recording medium substrate and a method for manufacturing the magnetic recording medium.

FIG. 13 shows the Rm of a glass substrate for a magnetic recording medium obtained by subjecting the surface of a glass substrate to a silicic acid treatment after a chemical strengthening treatment.
It is a figure which shows the relationship between ax and OBA% 3nm.

FIG. 14 is a diagram showing the relationship between Rmax and OBA% 3 nm of a magnetic recording medium glass substrate obtained by subjecting the surface of a glass substrate to sulfuric acid treatment after chemical strengthening treatment.

FIG. 15 shows the treatment time with silicic acid after chemical strengthening and R
It is a figure which shows the relationship with a.

FIG. 16 shows the treatment time with silicic acid after chemical strengthening and R
It is a figure showing the relation with max.

FIG. 17: Oxygen treatment time and O after chemical strengthening
It is a figure which shows the relationship with BA% 3nm.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) G11B 5/725 G11B 5/725 5/84 5/84 ZC (72) Inventor Masatoshi Shibui Shinjuku-ku, Tokyo 2-7-5 Nakaochiai Hoya Co., Ltd. (72) Inventor Nobuyuki Eto 2-7-5 Nakaochiai Shinjuku-ku, Tokyo Hoya Co., Ltd.

Claims (22)

[Claims] 1. An information recording medium substrate having a surface roughness of Rmax 15 nm or less, wherein the surface of the substrate has a bearing area value of 0.2% to 1.0%.
Information that a bearing area value (offset bearing area value) at a depth of 0.5 to 5 nm (predetermined slice level) from a bearing height (true peak height) corresponding to 0% is 90% or less. Substrate for recording media. 2. An information recording medium substrate having a surface roughness of Rmax 15 nm or less, wherein the surface of the substrate has a bearing area value of 0.2% to 1.
The bearing area value (offset bearing area value) must be 90% or less, when the slice level is the depth corresponding to 20 to 45% of Rmax from the bearing height (true peak height) corresponding to 0%. A substrate for an information recording medium, comprising: 3. The information recording medium substrate according to claim 1, wherein the information recording medium substrate is a glass substrate whose surface has been subjected to precision polishing and / or etching treatment. 4. An information recording medium having a surface roughness of Rmax 15 nm or less on a medium surface, wherein the medium surface of the information recording medium has a bearing height corresponding to a bearing area value of 0.2% to 1.0%. An information recording medium, wherein a bearing area value (offset bearing area value) at a depth of 0.5 to 5 nm (predetermined slice level) from (true peak height) is 90% or less. 5. An information recording medium having a surface roughness of Rmax 15 nm or less on a surface of a medium, wherein the medium surface of the information recording medium has a bearing height corresponding to a bearing area value of 0.2% to 1.0%. An information recording medium, wherein a bearing area value (offset bearing area value) is 90% or less when a slice level is a depth corresponding to 20 to 45% of Rmax from (true peak height). 6. The information recording medium according to claim 4, wherein a friction coefficient based on the surface roughness of the medium surface is 3 or less. 7. The method according to claim 4, wherein a correlation between a friction coefficient and an offset bearing area in an information recording medium on which various lubricants are formed is examined, and a lubricant that reduces frictional force due to the lubricant is employed. 7. The information recording medium according to 6. 8. The method according to claim 1, wherein the lubricant is PFPE (perfluoro al
kyl polyether), which has an ether bond in the main chain, has a-(OCF ₂ F ₂ ) m (OCF ₂ ) n-linear structure, and has a hydroxyl group as a terminal group. The information recording medium according to claim 7, wherein: 9. A step of immersing a glass substrate in a heated chemical strengthening treatment liquid and ion-exchanging ions on the surface layer of the glass substrate with ions in the chemical strengthening treatment liquid to chemically strengthen the glass substrate; Treating the surface of the raised glass substrate with a treatment liquid containing silicic acid. 10. A step of polishing a surface of a glass substrate,
A step of immersing the glass substrate in the heated chemical strengthening treatment liquid and chemically strengthening the glass substrate by ion-exchanging ions of the surface layer of the glass substrate with ions in the chemical strengthening treatment liquid. In the method, a step of controlling the surface of the glass substrate to a desired surface roughness by a chemical treatment before the step of chemically strengthening, the surface of the glass substrate pulled up from the chemical strengthening treatment solution is treated with a treatment solution containing silicic acid. A method of manufacturing a glass substrate for an information recording medium, comprising: 11. The chemical treatment according to claim 1, wherein the chemical treatment is performed with a treatment liquid containing at least one acid selected from sulfuric acid, phosphoric acid, nitric acid, hydrofluoric acid, and hydrofluoric acid, or an alkali. 11. The method for producing a glass substrate for an information recording medium according to item 10. 12. The concentration of said hydrofluoric acid is 0.01 to 0.01.
The method for producing a glass substrate for an information recording medium according to any one of claims 9 to 11, wherein the content is 10% by weight. 13. A method for manufacturing an information recording medium, comprising forming at least a recording layer on the surface of the glass substrate for an information recording medium obtained according to claim 9. 14. A method for managing a coefficient of friction based on a surface roughness of an information recording medium having a surface roughness of Rmax 15 nm or less, wherein a bearing curve is repeatedly measured by an AFM (atomic force microscope). , Maximum protrusion height (BA = 0
%), A bearing area value at which the measured value of the bearing height starts to fluctuate rapidly is determined, and a bearing height (true peak height) corresponding to the bearing area value is determined from a bearing curve. From the above, the correlation between the bearing area at a predetermined depth and the friction coefficient based on the surface roughness is examined by changing the predetermined depth, and from the correlation, the amount of change in the friction coefficient corresponds to this. A predetermined depth (predetermined slice level) at which the amount of change in the bearing area is large is determined, and the friction coefficient is managed based on the surface roughness using the bearing area value (offset bearing area value) at the predetermined slice level. A friction coefficient management method based on the characteristic surface roughness. 15. A method for managing a friction coefficient based on a surface roughness of an information recording medium having a surface roughness of Rmax 15 nm or less on a medium surface, wherein the maximum height (Rmax) measured by AFM is 0.5 to 7
A friction coefficient management method based on surface roughness, wherein a friction coefficient is managed based on surface roughness using a bearing area at a nm depth (slice level). 16. A method of managing a friction coefficient based on a surface roughness of an information recording medium having a surface roughness of Rmax 15 nm or less on a surface of the medium, wherein the maximum height (Rmax) obtained by AFM measurement is calculated from Rmax.
A friction coefficient management method based on surface roughness, wherein a friction area is managed based on a surface roughness using a bearing area when a depth corresponding to 20 to 40% of the slice level is set as a slice level. 17. An information recording medium manufacturing method for manufacturing an information recording medium having a desired medium surface based on the friction coefficient management method based on surface roughness according to claim 14. 18. A method for manufacturing a substrate for an information recording medium for reflecting the surface of the information recording medium substrate on the surface of the information recording medium to obtain a desired medium surface.
6, based on the friction coefficient management method based on the surface roughness,
A method of manufacturing an information recording medium substrate for manufacturing an information recording medium substrate having a desired substrate surface. 19. A method for managing the surface condition of an information recording medium substrate having a surface roughness of Rmax 15 nm or less, wherein a maximum protrusion is obtained when a bearing curve is repeatedly measured by an AFM (atomic force microscope). Height (BA = 0
%), The bearing area value at which the measured value of the bearing height starts to fluctuate rapidly is determined, and various AFM measurements excluding data from BA = 0% to the bearing area value at which the measured value of the bearing height starts to fluctuate rapidly A surface state management method characterized by using values. 20. A method for manufacturing a substrate for an information recording medium for manufacturing a substrate for an information recording medium having a desired substrate surface based on the surface state management method according to claim 19. 21. A method for managing the surface condition of an information recording medium having a surface roughness of Rmax 15 nm or less, wherein a maximum projection height is obtained when a bearing curve is repeatedly measured by an AFM (atomic force microscope). (BA = 0
%), The bearing area value at which the measured value of the bearing height starts to fluctuate rapidly is determined, and various AFM measurements excluding data from BA = 0% to the bearing area value at which the measured value of the bearing height starts to fluctuate rapidly A surface state management method characterized by using values. 22. An information recording medium manufacturing method for manufacturing an information recording medium having a desired medium surface based on the surface state management method according to claim 21.