JP2001316133A - Glass substrate method for manufacturing same and information recorder using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a smooth glass substrate for an information recorder with higher recording density, less record error and less head crash, and to provide an information recoder, an information display and an information communication apparatus using the substrate. SOLUTION: The substrate is subjected to scrubbing cleaning by a suspension and etched.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass substrate used for an information recording device represented by a hard disk, a liquid crystal display panel, and the like, and a method of manufacturing the same. Further, the present invention relates to an information recording device using the glass substrate.

[0002]

2. Description of the Related Art Glass is a multi-component non-crystalline composition and has properties such as high visible light transmittance, high homogeneity and high surface smoothness. Utilizing these characteristics, glass products are used for various purposes, and in recent years, they are often used in fields related to information recording, information display, or information communication. In an information recording apparatus, glass is used as a substrate for an information recording medium, and an optical characteristic or a magnetic thin film is formed on the glass substrate to constitute an information recording medium. Surface smoothness is an extremely important characteristic for an information recording medium substrate. For example, if the surface of a hard disk substrate has large irregularities, the magnetic head collides with the substrate, causing problems such as recording errors and head crashes. Also,
In other information recording apparatuses, the surface smoothness is inseparable from the improvement in recording density. Therefore, the glass substrate for an information recording medium prevents a recording error or a head crash of the information recording apparatus and improves the recording density due to its high surface smoothness. On the other hand, in an information display device, a glass substrate is used as, for example, a liquid crystal display substrate, and prevents polarization and irregular reflection by a high visible light transmittance, and enables dense pixel arrangement by a high surface smoothness.

In a hard disk, a collision between a glass substrate and a magnetic head occurs due to the presence of a protruding projection (hereinafter referred to as "asperity") on the surface of the glass substrate. Therefore, it is considered that the problem of the recording error and the head crash is solved by reducing or eliminating the asperity. Therefore, the central proposition of technical development relating to glass substrates for information recording media has been to enhance the surface smoothness.

In a hard disk, the higher the surface smoothness of the substrate, the smaller the gap (flying height) between the rotating substrate and the magnetic head and the higher the recording density. However, if the surface smoothness of the substrate becomes too high, another problem of adhesion between the magnetic head and the substrate arises. Here, the term "adhesion" means that the magnetic head is attached to the surface of the substrate and is damaged by a remarkable resistance. When this sticking occurs, the risk of head crash becomes extremely high.

[0005] Therefore, various ideas have been devised for the hard disk.
A stop (CSS) method is exemplified. The CSS system is a system in which a portion having a relatively large projection (CSS zone) is provided on a substrate, and the magnetic head slides on the CSS zone when the substrate is rotationally driven and decelerated and stopped. C
In the SS system, a portion (data zone) for recording and holding information and a CSS zone are separately provided on the substrate surface, and the surface smoothness is enhanced in the data zone, while a large number of uniform projections are intentionally provided in the CSS zone. . As a result, both improvement in information recording density and avoidance of the risk of head crash can be achieved. However, the molding of the CSS zone has to increase the surface smoothness of the substrate once and then separately provide a projection, which is disadvantageous in terms of productivity. The CSS zone may be formed by a tape burnishing method in which a film provided with protrusions in advance or a method of irradiating the surface of a glass substrate with laser.

In recent years, the recording density of hard disks has been greatly improved, and it is inevitable that the demand for narrowing the flying height will increase in the future. This means that the surface smoothness of the substrate is further improved. However, if the flying height becomes too small, the magnetic head glides while slightly fluctuating on the substrate, and thus the frequency of sudden contact with the substrate (sticking) increases. And
Along with the increase in the surface smoothness of the substrate, the resisting force (frictional force) at the time of sticking increases in a manner similar to the adhesion problem, and as a result, recording errors and head crashes are more likely to occur. That is, even when there is no asperity on the substrate surface, if the flying height is further reduced, a recording error or a head crash occurs. Conventionally, it has been considered that no recording error or head crash occurs during substrate rotation without asperity. However, if the surface smoothness becomes too high, these problems occur.

Therefore, it is necessary to prevent an excessive resistance from being applied to the magnetic head at the time of sticking, and it is conceivable to moderately roughen the substrate surface as a means for this. That is, protrusions smaller than asperities, that is, “fine protrusions” are uniformly and densely formed on the substrate surface, the contact area between the magnetic head and the substrate is reduced, and the resistance during sticking is reduced. The microprojections need to have a uniform height so that they can come into contact with the magnetic head at many points, and a robustness that is not destroyed by the impact of sticking.

As a method of forming the microprojections, there is a method of etching a multi-component glass substrate using a chemical such as an acid solution or an alkali solution. This method
It has been developed in view of the fact that multi-component glass contains a composite of a component weak to an acid or a component weak to an alkali. That is, when a multi-component glass substrate is immersed in an acid solution, a component weak to acid is selectively eluted, and its surface is uniformly corroded (etched). On the other hand, when immersed in an alkali solution, components weak to alkali are selectively eluted and etched as described above. Since etching is not a mechanical process, it is theoretically possible to process the substrate surface uniformly and at the atomic unit level. On the other hand, in the mechanical and physical treatments such as the tape burnish method and the laser irradiation method, the desired accuracy cannot be obtained in the size, height, and periodicity of the projections formed.

[0009]

However, the prior art has the following problems. As described above, in the etching treatment, theoretically, the surface of the multi-component glass substrate is uniformly etched, and no asperity should be formed. However, in actuality, asperity may exist on the surface of the glass substrate even after performing the etching process. As a result of earnest studies on this phenomenon, the present inventors have presumed that asperity remains or occurs by the following mechanism. That is, in the surface layer of the solid solution, the composition is generally not necessarily uniform, and a component weak to an acid and a component weak to an alkali are unevenly distributed. In addition, the polishing material adheres or is buried in the substrate surface at the time of polishing, and there is a portion like a lid on the substrate surface. for that reason,
On the surface of the glass substrate, there are portions that are well soluble in the etching solution and portions that are not, resulting in non-uniform etching and asperity.

The present invention has been made in view of the above-mentioned problems. It is an object of the present invention to provide a glass substrate for an information recording medium and a method for manufacturing the same, which contribute to improving the information recording density and preventing the occurrence of recording errors and head crashes in an information recording apparatus. Also,
An object of the present invention is to provide a higher performance information recording, information display or information communication device by using the glass substrate having a high surface smoothness for various uses.

[0011]

To achieve the above object, a method for manufacturing a glass substrate according to the first aspect of the present invention comprises:
This is a combination of scrub cleaning using a suspension and etching.

According to a second aspect of the present invention, there is provided a method of manufacturing a glass substrate according to the first aspect of the present invention, wherein an etching process is performed, followed by scrub cleaning using a suspension.

According to a third aspect of the present invention, in the method of the second aspect, after the scrub cleaning using the suspension, an etching process is further performed.

According to a fourth aspect of the present invention, in the method of manufacturing a glass substrate according to the first aspect of the present invention, the etching treatment uses an acid solution and an alkali solution.

According to a fifth aspect of the present invention, in the method for manufacturing a glass substrate according to any one of the first to fourth aspects, the scrub cleaning mainly includes silicon dioxide (SiO ₂ ) or manganese oxide. A suspension of particles as a component is used.

According to a sixth aspect of the present invention, a scrub cleaning using a polishing pad is performed after the etching process without using a suspension.

According to a seventh aspect of the present invention, in the method of the sixth aspect, an alkaline solution is used for scrub cleaning.

The glass substrate of the invention according to claim 8 is
The average surface roughness Ra per 0.01 mm ² is 2.0 nm or less, and no protrusions of 10 nm or more are present.

The glass substrate according to the ninth aspect of the present invention is the glass substrate according to the eighth aspect, wherein the number of microprojections having a height of ² to 10 nm per 0.01 mm ² is 5 × 10 ^{2 to} 5 × 10 ^7. belongs to.

An information recording apparatus according to a tenth aspect of the present invention uses the glass substrate according to the eighth or ninth aspect.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. In addition, it is not limited to this embodiment.

According to the present invention, the surface of a glass substrate is processed by combining scrub cleaning using a suspension and etching. Scrub cleaning using a suspension is performed after final polishing (final polishing), which is the final treatment of the polishing process, and is not the polishing of the substrate surface, but the removal of foreign substances and scratches adhered thereto or the method described later. The purpose is to remove asperities formed by the etching process. Before and after the scrub cleaning and the etching process are not particularly limited, but the purpose and function of the scrub cleaning before and after the etching process are different. That is, in the case where scrub cleaning is performed before the etching process, the scrub cleaning aims to remove foreign substances and scratches adhering to the substrate surface and prevent asperity from being formed by the etching process. On the other hand, when scrub cleaning is performed after the etching process, the purpose is to remove asperities formed on the substrate surface.

At present, in the production of a glass substrate, it is essential to polish the surface of the substrate using an abrasive such as cerium oxide in order to remove the handling flaws and the like to enhance the surface smoothness. In this surface polishing, since the abrasive is pressed against the substrate surface with a considerable pressure, the abrasive is embedded in the substrate surface,
Moreover, a scratch may be left. Further, an abrasive such as cerium oxide has high reactivity (has an affinity) with glass, and thus may continue to adhere to the substrate surface even after polishing is completed. These residual abrasives and scratches
This is to reduce the surface smoothness of the substrate. Also, if the substrate is etched with the abrasive remaining, the portion to which the abrasive has adhered is not etched as if it were covered, and remains / formed as asperity. Therefore, by performing scrub cleaning using a suspension before the etching treatment, abrasives and scratches remaining on the substrate surface are removed, so that the glass substrate surface can be uniformly etched.

In the scrub cleaning using the suspension before the etching treatment, the surface of the substrate is rubbed with a pad to remove foreign substances and scratches adhering to the substrate surface. The suspension is used to enhance the ability to remove foreign matter, lubricate the contact between the substrate and the pad, and facilitate the removal of foreign matter. The type of suspension is not particularly limited, but a suspension of particles containing silicon dioxide (SiO ₂ ) or manganese oxide as a main component is preferable.
Particles containing silicon dioxide as a main component are hard to adhere to a glass substrate and have excellent removability, while particles containing manganese oxide as a main component are easily oxidized and dissolved in a weakly acidic hydrogen peroxide solution or the like. So it has excellent removability. Examples of particles containing silicon dioxide as a main component include commercially available fumed silica and colloidal silica. The primary and secondary particle diameters of these particles are not particularly limited, but the primary particle diameter is preferably 3 nm to 1 μm, and the secondary particle diameter is 5 nm to 100 μm, due to restrictions on particle production conditions and the like. Further, the shape of the primary and secondary particles is not particularly limited to a spherical shape or a polygonal cross section, and may be such a particle in which such particles are connected in a chain shape.

The concentration of the suspension is 0.001 to 40% by weight.
Is preferably 0.001 to 5% by weight,
More preferably, the content is 0.001 to 1% by weight. If this concentration is lower than 0.001% by weight, the suspension is practically almost as good as water, and the ability to remove foreign substances is hardly improved. Therefore, the suspensions of Comparative Examples 2 and 3 in the following Examples are not suspensions according to the present invention because their concentrations are less than 0.001% by weight. on the other hand,
If it is higher than 40% by weight, the viscosity of the suspension becomes too high, making it difficult for the suspension to penetrate between the substrate and the pad. In order to remove only asperity, it is preferable to use a concentration of 1% by weight or less.
This is because the higher the concentration of the suspension, the more the fine projections are ground. The temperature of the suspension is preferably from 10 to 60C. When the temperature is higher than 60 ° C., the evaporation rate of the solvent is increased, so that the above-mentioned problem due to a change in concentration is likely to occur. On the other hand, when the suspension freezes, its properties change, so it is necessary to use the suspension at a temperature that does not freeze.

The pads include foam type, non-woven type,
There are a suede type and a laminated type, and the material and structure are not particularly limited. If the pad is too soft, the contact with the substrate tends to be uneven, while if too hard, the particles of the suspension adhere to the substrate,
Problems such as scratches occurring when hard particles enter are separately caused. Therefore, the pad preferably has an indentation hardness (Asker hardness C) of 60 ° to 95 °.

The method by which the pad scrubs the surface of the glass substrate is not particularly limited. For example, a method in which a cylindrical pad is rotated so that the circumferential surface thereof is in contact with the substrate, and is slid in parallel with the rotation axis, There is a method of uniformly contacting the substrate and the pad surface while rotating the flat pad. The method of applying the suspension to the substrate is not particularly limited, but it is preferable to supply the suspension from the center of the rotating flat pad. This is because the suspension automatically flows outward from the center of the flat pad due to the centrifugal force, and a new suspension is constantly supplied over the entire surface of the flat pad, so that the above-described foreign matter removing ability is enhanced. Further, accumulation of contamination between the substrate and the flat pad is also reduced by the self-cleaning action, and the degree of surface cleaning of the substrate is increased.

The pressing pressure of the pad in the scrub cleaning using the suspension is from 9.8 × 10 ^{2 to} 1.96 × 10 ⁶ Pa (1
0 to 2,000 gf / cm ² ), preferably 9.8 × 1
0 ^{2 to} 1.96 × 10 ⁵ Pa (10 to 200 gf / cm ² ) is preferable. If the pressing pressure is smaller than 9.8 × 10 ² Pa, it is difficult to rotate the substrate stably, while 1.96
If it is larger than × 10 ⁶ Pa, pad wear becomes severe.
When the purpose is to remove asperity, the pressing pressure is preferably set to 1.96 × 10 ⁵ Pa or less.
This is because if it is higher than 1.96 × 10 ⁵ Pa, fine projections will be cut.

The rotation speed of the platen on which the substrate is placed is 50 to 1,
000 rpm is preferred. If the rotation speed is lower than 50 rpm, it is difficult to rotate the glass substrate stably,
On the other hand, if the rotation speed is higher than 1,000 rpm, a problem occurs in terms of stability of the apparatus, such as blurring of the rotation axis of the surface plate.

Further, the processing time of the scrub cleaning using the suspension is preferably 2 seconds to 10 minutes, particularly preferably 2 to 200 minutes.
Seconds are preferred. If the time is shorter than 2 seconds, the scrubbing device is difficult to operate stably. In order to remove only the asperity, it is preferable to set the time to 200 seconds or less. This is because if the scrub time is long, the minute projections are also cut to some extent.

In the etching treatment, uniform and dense minute projections are formed on the surface of the glass substrate by utilizing the composition of the glass substrate, that is, the fact that it is a multi-component system. That is, a multi-component glass substrate has a different elution rate for an etching solution for each component contained therein, and a specific component can be selectively eluted from the substrate surface by appropriately combining the composition of the substrate and the etching solution. . As a result, the substrate surface is densely and uniformly roughened. As the etching solution, either an acid solution or an alkali solution, or these may be used alternately.

For example, when a glass substrate is immersed in an alkali solution after an acid solution, minute projections are formed by the following mechanism. First, in an acid solution, a component weak to an acid is selectively eluted from the substrate surface, the surface is slightly roughened, and a porous layer made of a component resistant to an acid remains there.
Subsequently, when this glass substrate is immersed in an alkaline solution, the alkali-sensitive components in the porous layer are eluted, and the porous layer is further roughened to form finer fine projections. That is, by sequentially immersing the substrate in an acid solution and an alkali solution, components having a high elution rate in each solution are selectively eluted from the substrate surface, and finally, components that are hardly dissolved in both the acid solution and the alkali solution. Only remains. As a result, debris not eluted in the acid solution and the alkali solution forms microprojections. In the case of etching a glass substrate, the substrate surface can be roughened by the above mechanism even when only one of an acid solution and an alkali solution is used. However, by using an acid solution and an alkali solution in combination, the components to be eluted can be selected more intentionally, and finer and denser fine projections can be formed. Components that are weak to acids in the substrate composition include:
Examples include alkali metal oxides, alkaline earth metal oxides, and aluminum oxides. On the other hand, components that are weak to alkali include silica, titania, and zirconia oxide.

As described above, after the etching treatment, the strength of the glass substrate slightly decreases because the surface of the glass substrate becomes a porous layer. Therefore, after the etching treatment, scrub cleaning using a suspension may be performed to selectively remove minute projections having extremely low strength. If scrub cleaning using a suspension is not performed before the etching treatment, asperity is formed by the etching treatment, and it is necessary to remove the asperity. In this scrub cleaning, the healthy substrate surface is not affected (not shaved), but the porous and brittle microprojections and asperities are selectively removed. In other words, by performing the scrub cleaning after the etching process, only minute projections and asperities having extremely low strength are removed, and a moderately rough surface shape of the substrate is maintained. Then, by repeating the etching process and the scrub cleaning using the suspension alternately a plurality of times, a more uniform, dense and highly durable substrate having fine projections is formed.

Examples of the polishing agent that can be used in the polishing step of the glass substrate include cerium oxide, manganese oxide, zirconia oxide, aluminum oxide, titania, magnetite oxide, silicon dioxide and diamond. Among these, abrasives containing cerium oxide are most commonly used. Since the polishing agent containing cerium oxide forms a smooth polished surface in a short time, it is effective in suppressing the manufacturing cost of the substrate. However, as described above, since cerium oxide has high reactivity with glass, when an abrasive containing the same is used, the particles tend to remain on the surface of the glass substrate. Therefore, after polishing with an abrasive containing cerium oxide, scrub cleaning is preferably performed using a suspension containing particles mainly composed of silicon dioxide. Also,
When this suspension is used, it is preferable that scrub cleaning is further performed using an alkaline solution having a pH of 8 or more after scrub cleaning. This is because the re-scrub cleaning generates a repulsive force such as an electrostatic repulsive force between the abrasive once separated from the substrate and the substrate, thereby preventing re-adhesion. Examples of the alkaline solution having a pH of 8 or more include potassium hydroxide (KO
H) aqueous solution, sodium hydroxide (NaOH) aqueous solution, cathode water or hydrogenated water obtained by electrolysis, and the like. Examples of the hydrogenated water include pure water to which hydrogen is added and hydrogen to an alkaline solution.When hydrogen is added, degassed water from which dissolved air has been removed to enhance reducibility. It is preferable to use

As described above, when the scrub cleaning using the suspension is performed after the etching process, the asperities formed by the etching process are removed by the scrub cleaning. This is believed to be the function achieved in the scrub wash due to the presence of the suspension. However, if a polishing pad is used, asperity can be removed without using a suspension. Here, the polishing pad is a pad having high hardness (Asker hardness C is 60 ° to 95 °).
For example, "Surfing" manufactured by Fujimi Incorporated and "IC Suba Suprem" manufactured by Rodale Nitta
e "," Segal AM "manufactured by Daiichi Race Co., Ltd. or" RT, N, KE "manufactured by Kanebo. The conditions for using the polishing pad may be the same as those for the scrub cleaning using the suspension described above. It is considered that the reason why the asperity is effectively removed by the polishing pad is that the surface shape and hardness of the polishing pad are appropriate and the asperity of the substrate can be reliably contacted.

In the scrub cleaning using the polishing pad, the suspension is unnecessary, and asperity can be removed even with pure water. However, the use of an alkaline solution, particularly an aqueous solution of potassium hydroxide (KOH), further enhances the ability to remove asperities. This is because KOH has the effect of breaking the asperity by breaking the Si—O bonds that constitute the glass skeleton. In addition, in the alkaline solution, the electrostatic repulsion acts, and it becomes difficult for the removed asperity to adhere to the substrate again.

The type of substrate is not particularly limited, and soda lime glass, borosilicate glass, aluminoborosilicate glass, aluminosilicate glass, crystallized glass, and the like, which are currently used for various applications, can be used. In particular, as a glass substrate for an information recording medium, aluminosilicate glass is preferable in terms of weather resistance and cost. These substrates may have a compressive stress layer formed on the surface of the substrate by chemical strengthening.

The glass substrate manufactured by the above-described manufacturing method has a surface
It has extremely high smoothness and is suitable for use with an atomic force microscope (hereinafter referred to as “AF
M ”) is 0.01 mm^Two(0.
1 × 0.1 mm) with an average surface roughness Ra of 0.4 to 2.0 nm
And protrusions of at least 10 nm,
Has no tee at all. Furthermore, this substrate is 0.01 mm
^Two5 x 10 nm micro-projections^Two~ 5 × 10⁷Private
Is what you do. The surface of this substrate is etched.
Even if a porous layer is present due to the
Cleaning or scrub cleaning using a polishing pad.
Finely degraded microprojections are removed. So this
Glass substrates are used as glass substrates for information recording media
Heading will occur if you stick
Absent.

An information recording apparatus using this glass substrate
The information recording density is further improved by the high surface smoothness of the substrate. Moreover, the adhesion of the magnetic head to the substrate is prevented by the large number of minute projections formed on the substrate, and the reliability of information recording is improved. This glass substrate is used as a glass substrate in applications requiring higher surface smoothness, in addition to glass substrates for information recording media. For example, when used for a liquid crystal display substrate, an information display device with a fine pixel arrangement can be obtained.

[0040]

EXAMPLES The present invention will be described more specifically below with reference to examples. However, it is not limited to the following embodiments.

Example 1 A glass substrate for an information recording medium was manufactured by the following method. 1.0mm thick aluminosilicate glass (66.0mol% SiO2, 11.0mol Al2O3)
%, 8.0 mol% of Li2O, 9.0 mol% of Na2O, 2.4 mol of MgO
_{%, CaO 3.6mol%, K 2} O 0.2mol%, SrO2.0mol%)
, A donut plate having an outer diameter of 65 mm and an inner diameter of 20 mm was cut out. This donut plate is subjected to a conventional lap, polish, and final polish polishing process to obtain a thickness of 0.
The surface was polished to 6 mm. The final polish is polished using a polishing agent containing cerium oxide (CeO2) (Mirek, manufactured by Mitsui Kinzoku Mining Co., Ltd.) and a suede pad, washed with a shower of pure water, and weakly adhered to the substrate surface. Was removed. The etching rate of this substrate with a 0.1% by weight aqueous solution of hydrofluoric acid at a temperature of 50 ° C. was 113 nm / min.

Then, 0.01% by weight maintained at 50 ° C.
The substrate was immersed in a bath of a hydrofluoric acid solution for 2.5 minutes, and irradiated with ultrasonic waves of about 48 kHz and 1 W / cm ² for 2.5 minutes. Thereafter, a commercially available alkaline solution (pH 11
The substrate was immersed in a bath of Chemical Products Co., Ltd. RB25) for 2.5 minutes, and irradiated with ultrasonic waves of about 48 kHz and 1 W / cm ² for 2.5 minutes. The substrate was pulled out of the alkaline solution bath, immersed in a pure water bath, and rinsed to remove the alkaline solution. This series of etching processes is hereinafter referred to as “first etching process”.

Subsequently, a flat pad (a suede pad made of urethane and SUBA800 made by Rodale Nitta) and a suspension having a solid content concentration of 0.001% by weight (colloidal silica suspension Planerlight 4101 made by Fujimi Incorporated) were used. Was used to perform a scrub wash with the suspension for 5 seconds. At this time, the number of rotations of the pad was 700 rpm, and the pressing pressure of the pad was 980 Pa (10 gf / cm
² ) and 30ml per minute from the center of the rotating flat pad
Supplied the suspension. Thereafter, the above-mentioned flat pad was supplied with an aqueous solution of potassium hydroxide having a pH of 11 from the center of the pad at a rotational speed of 700 rpm at a rate of 100 ml / min, and scrub cleaning was performed for 30 seconds.

Finally, the substrate was rinsed three times in a pure water bath,
After being immersed in a bath of isopropyl alcohol and irradiated with ultrasonic waves of about 48 kHz for 2 minutes, it was dried in isopropyl alcohol vapor for 1 minute. Hereinafter, this process is referred to as “final cleaning”.
That.

(Examples 2 and 3) In scrub washing using a suspension, the solid content of the suspension was adjusted to 0.01% by weight.
% And 0.1% by weight, and a glass substrate was produced in the same manner as in Example 1 except that the treatment time was changed to 10 seconds.

(Examples 4 and 5) In the scrub washing using the suspension, the solid content of the suspension was adjusted to 1.0% by weight.
A glass substrate was manufactured in the same manner as in Example 1 except that the glass substrate was changed to 5.0% by weight.

Example 6 In scrub cleaning using a suspension, the solid concentration of the suspension was set to 0.01% by weight, and the pressing pressure of the flat pad was set to 1.96 × 10 ⁴ Pa (200 gf / c).
A glass substrate was manufactured in the same manner as in Example 1 except that the glass substrate was changed to m ² ).

Example 7 In scrub cleaning using a suspension, the pressing pressure of a flat pad was set to 4.9 × 10 ⁴ Pa (5
A glass substrate was manufactured in the same manner as in Example 1, except that the glass substrate was changed to 00 gf / cm ² ).

Example 8 A glass was prepared in the same manner as in Example 1 except that the solid content of the suspension was changed to 0.01% by weight and the treatment time was changed to 200 seconds in the scrub cleaning using the suspension. A substrate was manufactured.

Example 9 A glass substrate was manufactured in the same manner as in Example 1 except that the treatment time was changed to 300 seconds in scrub cleaning using a suspension.

(Example 10) In scrub cleaning using a suspension, the solid concentration of the suspension was changed to 0.01% by weight, and before the final cleaning, etching was performed again under the same conditions as the first etching. (Second etching process) was performed. Otherwise, a glass substrate was manufactured in the same manner as in Example 1.

(Embodiment 11) After the second etching process in Example 10, an etching process (third etching process) was performed again under the same conditions. Otherwise, Example 10
A glass substrate was manufactured in the same manner as described above.

(Examples 12 and 13) In Example 11, except that the concentration of the hydrofluoric acid solution was changed to 0.03% by weight and 0.05% by weight in the third etching treatment.
A glass substrate was manufactured in the same manner as described above.

Comparative Example 1 A glass substrate was manufactured in the same manner as in Example 1 except that scrub cleaning using a suspension was not performed.

(Comparative Example 2) A glass substrate was manufactured in the same manner as in Example 1 except that the solid content of the suspension was changed to 0.0005% by weight in scrub cleaning using the suspension.

(Comparative Example 3) A glass substrate was manufactured in the same manner as in Example 11, except that the solid content of the suspension was changed to 0.0005% by weight in scrub cleaning using the suspension.

[Evaluation of Glass Substrate] Examples 1 to 13
The surface smoothness of the glass substrates of Comparative Examples 1 to 3 was measured using a scanning probe microscope: AFM (NanoscopeIIIa manufactured by Digital Instruments). This measurement is
Average surface roughness Ra observed at 20 × 20 μm,
10 to 10 nm (average over 25 visual fields)
The number of protrusions of 0 nm or more, that is, the number of asperities (average for 20 visual fields) is measured. The number of asperities was adjusted so that the total visual field area of the AFM measurement was 0.01 mm ² due to the problem of existence probability.

[0058]

[Table 1]

(Examples 14 to 16) Scrub cleaning was performed on the glass substrates manufactured in Comparative Examples 1 to 3 using a polishing pad (Seagull 1900 manufactured by Daiichi Race Co., Ltd.) without using a suspension. Was. The condition of this scrub cleaning is p
An aqueous solution of potassium hydroxide of H12 was supplied from the center of the polishing pad at a rate of 100 ml / min.
pm and a pressing pressure of 4.9 kPa (50 gf / cm ² ) for 10 seconds. This substrate was finally washed, and the glass substrate was evaluated in the same manner as described above. The results are shown in Table 2 below.

[0060]

[Table 2]

By comparing Examples 1 to 13 with Comparative Example 1, it can be seen that when etching treatment and scrub cleaning are combined, Ra is suppressed to about 1 nm and asperity is surely removed.

By comparing Example 1 with Comparative Example 2 and Example 11 with Comparative Example 3, if the solid concentration of the suspension in the scrub cleaning is less than 0.001% by weight, It can be seen that the asperity cannot be removed with the pad.

By comparing Example 1 with Example 5, it can be seen that when the solid content concentration of the suspension in scrub cleaning is increased, the number of projections is reduced, that is, fine projections other than asperity are ground.

By comparing Example 1 with Example 7, it can be seen that when the pressing pressure of the pad is increased, the number of projections is reduced even if other conditions (density, processing time) are mild.

By comparing Example 1 and Example 9, it can be seen that if the processing time in scrub cleaning is increased, the number of projections is reduced even if other conditions (concentration and pressing pressure) are mild.

By comparing Example 1, Example 10 and Example 11, when the number of etching processes increases,
It can be seen that the number of microprojections increases.

By comparing Examples 11 to 13 with each other, it can be seen that when the concentration of the acid solution in the etching treatment increases, the number of the fine projections increases.

By comparing Examples 14 to 16 with Comparative Examples 1 to 3, it can be seen that asperity can be removed without using a suspension by using a polishing pad.

[0069]

According to the present invention having the above-described structure, the following effects can be obtained. According to the first aspect of the present invention, since the scrub cleaning and the etching using the suspension are performed, the asperity is completely removed from the substrate surface, and a large number of minute projections are formed.

According to the invention described in claim 2, according to claim 1
In addition to the effects of the invention, the etching process is performed, followed by the scrub cleaning using the suspension, so that the asperities formed by the etching process are reliably removed.

According to the invention described in claim 3, according to claim 2
In addition to the effects of the invention, the etching process is further performed after the scrub cleaning using the suspension, so that the number of microprojections can be increased without forming asperities.

According to the invention set forth in claim 4, according to claim 1
In addition to the effects of the inventions of (1) to (3), since the acid solution and the alkali solution are used in the etching treatment, the fine projections can be formed more densely.

According to the invention described in claim 5, claim 1 is provided.
In addition to the effects of the inventions of ( ₁ ) to ( ₄ ), since a suspension of particles containing silicon dioxide (SiO ₂ ) or manganese oxide as a main component is used in the scrub cleaning, these particles hardly remain on the substrate surface, and the etching treatment is performed. Can suppress the formation of asperities.

According to the sixth aspect of the present invention, the scrub cleaning using the polishing pad is performed after the etching process, so that the asperities formed by the etching process can be surely removed without using a suspension. be able to.

According to the invention of claim 7, according to claim 6,
In addition to the effects of the invention, the use of an alkaline solution in the scrub cleaning makes the asperities brittle and easy to remove, and also prevents the removed asperities from re-adhering to the substrate.

According to the eighth aspect of the present invention, 0.01
Since the average surface roughness Ra per mm ² is not more than 2.0 nm and there are no protrusions of not less than 10 nm, if it is used, for example, as a glass substrate for an information recording medium, the information recording density of the information recording apparatus is improved. be able to.

According to the ninth aspect of the present invention, an eighth aspect is provided.
0.01mm in addition to the effect of the invention of ^TwoHit height 2
The number of micro-projections of 10 nm is 5 × 10^Two~ 5 × 10⁷Individual
Therefore, it can be used as a glass substrate for information recording media, for example.
Head crack caused by the adhesion between the magnetic head and the substrate
The occurrence of shrinkage can be suppressed.

According to the tenth aspect of the present invention, an information recording apparatus having a high recording density and high reliability can be obtained.

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Claims (10)

[Claims] 1. A method for manufacturing a glass substrate, comprising a combination of scrub cleaning using a suspension and etching. 2. The method of manufacturing a glass substrate according to claim 1, wherein said etching treatment is performed, and subsequently, scrub cleaning using a suspension is performed. 3. The method of manufacturing a glass substrate according to claim 2, wherein an etching process is further performed after the scrub cleaning using the suspension. 4. The method according to claim 1, wherein the etching process uses an acid solution and an alkali solution.
Item 13. The method for producing a glass substrate according to item 1. 5. The method of claim 1, wherein the scrub cleaning is performed using silicon dioxide (SiO 2).
₂ ) The method of manufacturing a glass substrate according to any one of claims 1 to 4, wherein a suspension of particles containing manganese oxide as a main component is used. 6. A method for manufacturing a glass substrate, comprising: performing scrub cleaning using a polishing pad without using a suspension after an etching process. 7. The method for manufacturing a glass substrate according to claim 6, wherein the scrub cleaning uses an alkaline solution. 8. Average surface roughness Ra per 0.01 mm ²
Is a glass substrate having a thickness of 2.0 nm or less and having no projections of 10 nm or more. 9. The glass substrate according to claim 8, wherein the number of protrusions having a height of ² to 10 nm per 0.01 mm ² is 5 × 10 ^{2 to} 5 × 10 ⁷ . 10. An information recording apparatus using the glass substrate according to claim 8.