WO2016017812A1

WO2016017812A1 - Magnetic disk-use glass substrate manufacturing method and magnetic disk manufacturing method

Info

Publication number: WO2016017812A1
Application number: PCT/JP2015/071854
Authority: WO
Inventors: 俵　義浩
Original assignee: Hoya株式会社
Priority date: 2014-07-31
Filing date: 2015-07-31
Publication date: 2016-02-04
Also published as: CN106537505B; JPWO2016017812A1; CN106537505A; JP6282741B2; MY176437A; SG11201610744YA

Abstract

The present invention provides a magnetic disk-use glass substrate manufacturing method by which the surface roughness of a glass substrate main surface can be reduced even more than by existing methods, and by which surface defects can also be greatly reduced. This magnetic disk-use glass substrate manufacturing method includes processing for reducing the roughness of the main surface of the glass substrate by using a processing liquid which contains, as an abrasive, organic particles comprising, for example, styrene resin, acrylic resin, or urethane resin. In order to reduce foreign-matter adherence defects on the glass substrate surface which was subjected to the abovementioned processing, the organic particles are classified so as to reduce, for example, the number of the particles having a diameter of 3μm or less, such particles included in the organic particles.

Description

Manufacturing method of glass substrate for magnetic disk and manufacturing method of magnetic disk

The present invention relates to a method for manufacturing a glass substrate for a magnetic disk used for a magnetic disk mounted as an information recording medium of a magnetic recording device such as a hard disk drive (hereinafter abbreviated as “HDD”), and a method for manufacturing a magnetic disk. .

There is a magnetic disk as one of information recording media mounted on a magnetic recording apparatus such as an HDD. A magnetic disk is configured by forming a thin film such as a magnetic layer on a substrate, and an aluminum substrate has been conventionally used as the substrate. However, recently, in response to the pursuit of higher recording density, the ratio of the glass substrate capable of narrowing the distance between the magnetic head and the magnetic disk as compared with the aluminum substrate is gradually increasing. Further, the surface of the glass substrate is polished with high accuracy so as to increase the recording density so that the flying height of the magnetic head can be reduced as much as possible. In recent years, there has been an increasing demand for HDDs with higher recording capacity and lower prices. In order to achieve this, it is necessary to further improve the quality and cost of glass substrates for magnetic disks. It is coming.

As described above, high smoothness on the surface of the magnetic disk is indispensable for reducing the flying height (flying height) necessary for increasing the recording density. In order to obtain a high smoothness on the surface of the magnetic disk, a substrate surface with a high smoothness is required in the end. Therefore, it is necessary to polish the glass substrate surface with high accuracy.
A conventional glass substrate polishing method is performed using a polishing pad of a polisher such as polyurethane while supplying a slurry (polishing liquid) containing a metal oxide abrasive such as cerium oxide or colloidal silica. A glass substrate having high smoothness can be obtained by polishing using, for example, a cerium oxide-based abrasive and then finishing polishing (mirror polishing) using colloidal silica abrasive grains.

JP 2011-136402 A

In current HDDs, for example, it is possible to store about 320 gigabytes of information per disk on a 2.5 inch type (65 mm diameter) magnetic disk. However, even higher recording density such as 750 is possible. The realization of a gigabyte or even 1 terabyte is being demanded. With the recent demand for larger capacity of HDDs, the demand for improvement of the substrate surface quality has become more severe than ever. In the next generation substrate for a magnetic disk of, for example, 750 gigabytes as described above, since the influence of the substrate on the reliability of the HDD is increased, further improvement of the substrate surface roughness from the current product is required.

In the next generation substrate, the influence of the substrate on the reliability of the HDD becomes large for the following reason.
For example, the flying height of the magnetic head (the gap between the magnetic head and the surface of the medium (magnetic disk)) is greatly reduced (lower flying height). By doing this, the distance between the magnetic head and the magnetic layer of the medium is reduced, so that signals can be written to smaller areas and signals of smaller magnetic particles can be picked up, achieving higher recording density. can do. In recent years, a function called DFH (Dynamic Flying Height) control is mounted on a magnetic head. This does not reduce the flying height of the slider, but uses the thermal expansion of a heating part such as a heater built in the vicinity of the recording / reproducing element part of the magnetic head, so that only the recording / reproducing element part protrudes toward the medium surface. This is a (closer) function. Under such circumstances, in order to realize a low flying height of the magnetic head, further smoothness of the glass substrate surface is required.

By the way, in the prior art, as a method of reducing the roughness of the main surface of the glass substrate, a method of refining the grain size of the abrasive grains used in the polishing step is well known.
However, according to the study of the present inventor, for example, in the case of colloidal silica abrasive grains used for conventional finish polishing, for example, even if one having an average particle diameter of 10 nm or less is used, the roughness of the glass surface after polishing tends to decrease. I can no longer see it. During polishing, the abrasive grains are interposed between the glass surface and the polishing pad, but since the polishing pad is pressed against the glass surface with a predetermined load, minute abrasive grains sink into the polishing pad. Therefore, it is presumed that the amount of protrusion contributing to polishing is reduced and the grinding amount is remarkably reduced, so that the effect of reducing the surface roughness due to polishing cannot be exhibited.

In addition, after the polishing, cleaning is performed for the purpose of removing the abrasive grains adhering to the glass surface. In the cleaning for removing inorganic abrasive grains such as colloidal silica, alkali cleaning is usually performed. Since the alkali component has an etching effect on glass, an increase in the roughness of the glass substrate surface after cleaning has been conventionally confirmed.

In particular, colloidal silica has the same degree of hardness as glass. Therefore, in polishing using colloidal silica as abrasive grains, a non-uniform work-affected layer is formed on the glass surface. The action is also considered to be involved in the increase in the roughness of the glass surface. For example, it is possible to suppress the formation of a non-uniform work-affected layer by making the abrasive grains finer, but as described above, if the abrasive grains are made finer, the effect of reducing the surface roughness by polishing cannot be obtained. .

In the above-mentioned Patent Document 1, the generation of scratches is suppressed by using composite particles (heteroaggregates) of organic particles and inorganic particles having a size equal to or larger than that of the organic particles as abrasive grains. It is disclosed.
However, in the abrasive grains disclosed in the above-mentioned Patent Document 1, it is considered that inorganic particles such as silica particles substantially exhibit a grinding action on glass, and polishing is performed using such abrasive grains. Even if processing is performed, it is difficult to fundamentally solve the conventional problems.

In short, for example, when aiming to manufacture next-generation substrates for 750 gigabyte magnetic disks, further improvement of the substrate surface roughness from the current product is required, for example, the surface roughness Ra is 0.1 nm or less. Therefore, there is a limit to the conventional roughness improving method, and it is difficult to develop the next generation substrate as described above.

Also, not only low surface roughness but also low surface defects are required strictly for next-generation substrates. Although it seems that the reduction of surface defects can be solved by cleaning after polishing, in order to sufficiently remove inorganic abrasive grains such as colloidal silica adhering to the glass surface after polishing, it is usually strong alkaline cleaning. It is necessary to apply conditions, and when such cleaning conditions are applied, there arises a problem that the roughness of the glass substrate surface after cleaning increases as described above. In other words, with the application of the prior art, it has been difficult to simultaneously solve the problems of both low surface roughness and low surface defects that satisfy the high level surface quality requirements required for next generation substrates.

Therefore, the present invention has been made to solve such a conventional problem, and its purpose is to reduce the surface roughness of the main surface of the glass substrate as compared with the present, and to greatly reduce surface defects. It is providing the manufacturing method of the glass substrate for magnetic discs which can be manufactured, and the manufacturing method of a magnetic disc using the glass substrate obtained by this manufacturing method.

Therefore, the present inventor reduced the surface roughness of the glass substrate in the polishing step and obtained the surface of the glass substrate in the cleaning step after polishing in order to obtain a glass substrate having a surface roughness further reduced than the current level. A method of not increasing the roughness was studied. As a result of the investigation, it was surprisingly found that the above-mentioned problem of reducing the surface roughness can be solved by using organic particles as abrasive grains.

That is, by applying a treatment using organic particles having a hardness lower than that of glass as polishing abrasive grains, polishing is considered to proceed without forming a non-uniform work-affected layer on the glass surface in the polishing step under load. The roughness of the glass substrate surface after polishing can be reduced, and the increase in the roughness of the glass substrate surface after cleaning can be suppressed by selecting a cleaning liquid that does not have an etching action on the glass. It has been found that, for example, the surface roughness Ra required for the generation substrate can be 0.1 nm or less.

As a result of further studies, the present inventor can significantly reduce the number of foreign matter adhesion defects on the surface of the glass substrate by classifying the organic particles used as abrasive grains. As a result, the next generation substrate is required. It has been found that low surface roughness and low surface defects can be realized at a high level.

Based on the above findings, the present inventor has completed the present invention.
That is, the present invention has the following configuration in order to achieve the above object.
(Configuration 1)
A method for producing a glass substrate for a magnetic disk, comprising a treatment for reducing the roughness of the main surface of a glass substrate using a treatment liquid containing organic particles as abrasive grains, and foreign matter on the surface of the glass substrate after the treatment A method for producing a glass substrate for a magnetic disk, wherein the organic particles are classified to reduce adhesion defects.

(Configuration 2)
2. The method for producing a glass substrate for a magnetic disk according to Configuration 1, wherein the organic particles are classified so as to reduce the number of particles having a particle size of 3 μm or less.
(Configuration 3)
3. The method for producing a glass substrate for a magnetic disk according to Configuration 2, wherein the number of particles having a particle size of 3 μm or less contained in the organic particles is classified so as to be 5% or less in the number particle size distribution. .

(Configuration 4)
4. The method for producing a glass substrate for a magnetic disk according to any one of Structures 1 to 3, wherein the classified organic particles have an average particle diameter in the range of 5 to 30 μm.
(Configuration 5)
5. The method of manufacturing a glass substrate for a magnetic disk according to any one of configurations 1 to 4, wherein the organic particles are made of a styrene resin, an acrylic resin, or a urethane resin.

(Configuration 6)
6. The method for manufacturing a glass substrate for a magnetic disk according to any one of Structures 1 to 5, wherein after the treatment, the surface of the glass substrate is subjected to a cleaning treatment under such a condition that the substrate surface roughness after the cleaning does not increase.
(Configuration 7)
After polishing the main surface of the glass substrate using a polishing liquid containing silica abrasive grains as polishing abrasive grains, a treatment for reducing the roughness of the main surface of the glass substrate using a processing liquid containing the organic particles as abrasive grains. The manufacturing method of the glass substrate for magnetic discs in any one of the structures 1 thru | or 6 characterized by performing.

(Configuration 8)
A magnetic disk manufacturing method comprising forming at least a magnetic recording layer on a glass substrate for a magnetic disk obtained by the manufacturing method according to any one of Structures 1 to 7.

According to the present invention, the surface roughness of the main surface of the glass substrate can be further reduced compared to the current surface by performing the processing of the main surface of the glass substrate using a treatment liquid containing classified organic particles as abrasive grains. In addition, it is possible to manufacture a high-quality glass substrate for a magnetic disk that can greatly reduce foreign matter adhesion defects on the glass substrate surface.
Further, the above configuration of the present invention makes it possible to manufacture a high-quality magnetic disk glass substrate suitable for manufacturing a magnetic disk having a higher recording density than ever before, for example, exceeding 750 gigabytes. It is.
Further, by using the glass substrate for magnetic disk obtained by the present invention, it is possible to manufacture a magnetic disk having a higher recording density than ever before, for example, exceeding 750 gigabytes.

It is a longitudinal cross-sectional view which shows schematic structure of a double-side polish apparatus.

Hereinafter, embodiments of the present invention will be described in detail.
A glass substrate for a magnetic disk is usually manufactured through a grinding process, a shape processing process, an end surface polishing process, a main surface polishing process, a chemical strengthening process, and the like.
In manufacturing the magnetic disk glass substrate, first, a disk-shaped glass substrate (glass disk) is molded from molten glass by direct pressing. In addition to such a direct press, a glass substrate may be obtained by cutting into a predetermined size from a plate glass manufactured by a downdraw method or a float method. Next, the main surface of the molded glass substrate is ground for improving dimensional accuracy and shape accuracy. In this grinding step, a main surface of the glass substrate is ground using a hard abrasive such as diamond, usually using a double-side grinding machine. By grinding the main surface of the glass substrate in this way, a predetermined plate thickness and flatness are processed, and a predetermined surface roughness is obtained.

After the grinding process is finished, after a shape processing process and an end surface polishing process, a mirror polishing process is performed to obtain a highly accurate flat surface. Conventionally, a mirror polishing method for a glass substrate has been performed using a polishing pad such as polyurethane foam while supplying a slurry (polishing liquid) containing a metal oxide abrasive such as cerium oxide or colloidal silica. .

As described above, when the inventor intends to manufacture a magnetic disk having a higher recording density than ever before, for example, exceeding 750 gigabytes, for example, a magnetic head having the above-described DFH control function is employed. In order to achieve further lower flying height, it is necessary to further reduce the roughness of the substrate surface, which can be a hindrance factor, compared to the current product. To that end, a treatment liquid containing organic particles as abrasive grains is used. Thus, it has been found that it is preferable to treat (polishing) the surface of the glass substrate.

In one embodiment of the present invention, for example, as a processing liquid (polishing liquid) composition applied to a polishing process for polishing a main surface of a glass substrate used for a magnetic disk, organic particles are included as abrasive grains. It is.
That is, by using organic particles having lower hardness and elasticity than glass as abrasive grains, polishing is considered to proceed without forming a non-uniform work-affected layer on the glass surface in the polishing process under load. The roughness of the subsequent glass substrate surface can be reduced. Moreover, since it is possible to perform cleaning by selecting a cleaning solution that does not have an etching action on the glass in the cleaning process for removing the abrasive grains adhering to the glass substrate surface after polishing, the glass substrate after cleaning An increase in surface roughness can be suppressed.

And by carrying out the polishing treatment of the glass substrate using a treatment liquid containing the organic particles according to the present invention as abrasive grains, the surface roughness of the glass substrate surface is required for the next generation substrate, for example, arithmetic average The roughness Ra can be reduced to 0.1 nm or less, and a high-quality glass substrate for a magnetic disk can be manufactured. Therefore, when manufacturing a magnetic disk having a higher recording density than ever, such as exceeding 750 gigabytes, a suitable high-quality glass substrate for a magnetic disk is manufactured in order to achieve a lower flying height than before. It is possible.

The treatment liquid (polishing liquid) applied to the polishing treatment is a combination of a polishing material (abrasive grains) and water as a solvent, and further includes a pH adjuster for adjusting the pH of the treatment liquid and other additives. It is contained as needed.

The treatment liquid (polishing liquid) contains organic particles as abrasive grains. These organic particles are particles made of a resin having lower hardness than glass and having elasticity. Specifically, the material is preferably made of an acrylic resin such as polymethyl methacrylate (PMMA), a urethane resin, or a resin material such as a styrene resin. The acrylic resin may be a homopolymer containing only an acrylic monomer component, or a copolymer of an acrylic monomer component (main component) and another type of monomer component. The urethane resin may be a homopolymer of only the urethane monomer component, or may be a copolymer of a urethane monomer component (main component) and another type of monomer component. The styrenic resin may be a homopolymer of only a styrene monomer component or a copolymer of a styrene monomer component (main component) and another type of monomer component. Especially, it is preferable to consist of an acrylic resin or a urethane resin from the viewpoint of good dispersibility in water and easy slurry formation. In addition, in the case of organic particles made of the above acrylic resin, not only a resin material made of a single acrylic monomer component but also organic particles made of a copolymer resin material containing a plurality of different acrylic monomer components can be used. . The same applies to organic particles made of urethane resin or styrene resin.

In the present invention, as in the configuration 1, it is important that the organic particles contained in the treatment liquid as abrasive grains are classified. Commercially available organic particles (for example, acrylic resin particles such as PMMA) include uncrosslinked or low-crosslinked fine resin particles that are inevitably generated by the production method. These can be said to be immature organic particles that could not be grown to the original resin particles. As a result of intensive studies, the present inventors have found that it is important to classify organic particles used as abrasive grains. That is, by removing as much as possible the specific particle size portion contained in the organic particles, and using the organic particles thus classified as abrasive grains, the low surface roughness of the glass substrate after processing is reduced. It has been found that the number of foreign matter adhesion defects on the surface of the glass substrate can be greatly reduced while being held. Compared with the substantially spherical main component particles in the organic particles, the above-mentioned non-crosslinked or low-crosslinked fine resin particles are presumed to be amorphous and have a large surface area and easily adhere to the glass substrate surface.
The present inventor conducted a detailed investigation on foreign matters on the substrate surface after polishing with organic particles using a scanning electron microscope (SEM), an energy dispersive X-ray analyzer (EDS), etc. I have determined that particles are the main cause. Furthermore, it has been found that the particle diameter of these fine resin particles is approximately 3 μm or less. That is, it has been found for the first time that the number of foreign matter adhesion defects on the glass substrate surface after polishing with organic particles can be greatly reduced by removing particles having a size of 3 μm or less.

That is, according to the present invention, the surface roughness of the main surface of the glass substrate is further reduced compared to the current surface by performing a polishing process on the main surface of the glass substrate using a treatment liquid containing classified organic particles as abrasive grains. In addition, foreign matter adhesion defects on the surface of the glass substrate can be greatly reduced. As a result, low surface roughness and low surface defects can be realized at a high level required for the next generation substrate. It is possible to manufacture quality glass substrates for magnetic disks.

According to the study of the present inventor, it is desirable to classify so as to reduce the number of particles having a particle size of 3 μm or less contained in the organic particles. As a result, it is possible to sufficiently remove the fine resin particles contained in the organic particles that are not crosslinked or have a low degree of crosslinking.
Further, according to further studies by the present inventor, more specific conditions for sufficiently obtaining the effect of greatly reducing the number of foreign matter adhesion defects on the glass substrate surface after the treatment are included in the organic particles. When the number of particles having a particle size of 3 μm or less is accumulated in the number particle size distribution, it is preferably classified to be 5% or less, more preferably 3% or less, and 2% or less. Even more desirable. That is, the number of particles having a particle size in the range of 0 to 3 μm is preferably 5% or less of the total number of particles. The number particle size distribution is a relationship in which the horizontal axis indicates the particle diameter (μm) and the vertical axis indicates the number (%).

The classification method is not particularly limited, and for example, a commercially available powder classifier can be used. As a commercially available classifier, classifiers such as a swirling airflow type, a Coanda airflow type, and a swivel screen type are known. In the present invention, classification is preferably performed so as to reduce the number of particles having a particle size of 3 μm or less contained in the organic particles, so it is desirable to appropriately set the classification conditions. Further, the classification is not limited to once, and may be repeated a plurality of times so that the preferable classification is performed.

As the shape of the organic particles, since it is necessary to have low friction in order to rotate the platen under a load, it is preferably substantially spherical, and resin beads having a uniform particle size are desirable. In the present invention, organic particles having a substantially spherical shape and a uniform particle diameter can be obtained by the above classification.

In the present invention, the average particle diameter of the classified organic particles is preferably in the range of 5 to 30 μm, more preferably 10 to 30 μm. When the average particle size is less than 5 μm, it becomes difficult to obtain processability for smoothing the substrate surface with respect to glass. In addition to the influence of the particle size itself, this is presumed to be because the shape of the organic particles tends not to be spherical. On the other hand, if the average particle size exceeds 30 μm, the viscosity of the treatment liquid increases and it becomes difficult to obtain processability for smoothing the good substrate surface.
In the present invention, it is particularly preferable to use those having an average particle size in the range of 10 to 20 μm from the viewpoint of further reducing the surface roughness.

In the present invention, the average particle size of the organic particles means that when the cumulative curve is obtained by setting the total volume of the powder population in the particle size distribution measured by the light scattering method as 100%, the cumulative curve is 50%. (Referred to as “cumulative average particle diameter (50% diameter)”, hereinafter abbreviated as “D50”). Specifically, the cumulative average particle size is a value obtained using a particle size / particle size distribution measuring apparatus.

The concentration of the organic particles in the treatment liquid is not particularly limited, but can be in the range of 0.1 to 5% by weight from the viewpoint of the substrate surface quality after treatment and the processing rate. In particular, the range of 1 to 3% by weight is preferable.

In addition, the treatment liquid containing organic particles used in the present invention is at least one additive selected from a material that exhibits a lubricating effect and a material that exhibits a moisturizing effect, from the viewpoint of reducing scratches due to adhesion of the resin by drying. It may contain.

Specific examples of such additives include glycols (ethylene glycol, propylene glycol, hexylene glycol, etc.), amines (monoethanolamine, diethanolamine, triethanolamine, isopropanolamine, etc.), carboxylic acid, mineral oil, water-soluble Oily emulsion, polyethyleneimine, boric acid, amide, triazines, benzothiazole, benzotriazole, ethers, and the like.
The addition amount of the additive is not particularly limited, but is preferably in the range of 0.01 to 1% by weight from the viewpoint of workability.

Further, the treatment liquid is used as, for example, a polishing liquid. In this case, for example, a liquid adjusted to pH = 4 to 8 is preferably used. If the pH is less than 4, there is a concern about erosion of the resin abrasive grains. On the other hand, if the pH exceeds 8, the cleaning property after polishing is lowered and foreign matter defects are likely to occur.

For example, in the polishing process using the processing liquid containing the organic particles of the present invention as abrasive grains, the polishing method is not particularly limited, but, for example, as in the prior art, the glass substrate and the polishing pad are brought into contact, The surface of the glass substrate may be polished into a mirror surface by relatively moving the polishing pad and the glass substrate while supplying a treatment liquid containing organic particles as abrasive grains. As the polishing pad, for example, the same one as a polishing pad made of foamed polyurethane, which is applied in a mirror polishing process using conventional colloidal silica abrasive grains, can be applied. However, in the mirror polishing process using the abrasive grains of the organic particles of the present invention, the hardness of the polishing pad is not limited to that of silica abrasive grains. This is because the resin abrasive grains themselves have pad cushioning properties. Therefore, in the mirror polishing process using the organic particle abrasive grains of the present invention, a polishing pad harder than, for example, a foamed polyurethane polishing pad applied in the conventional mirror polishing process using colloidal silica abrasive grains is applied. It is also possible. Use of a hard polishing pad is advantageous because the waviness of the substrate surface can be reduced. The hardness of the polishing pad is preferably 70 to 90 in terms of Asker C hardness, and more preferably 80 to 90. Furthermore, a suede-type foamed polyurethane polishing pad is more preferable because the generation of fine scratches can be reduced.

For example, FIG. 1 is a longitudinal sectional view showing a schematic configuration of a planetary gear type double-side polishing apparatus that can be used in a mirror polishing process of a glass substrate. The double-side polishing apparatus shown in FIG. 1 meshes with the sun gear 2, the internal gear 3 arranged concentrically on the outer side, the sun gear 2 and the internal gear 3, and the sun gear 2 and the internal gear 3. An upper surface plate 5 and a lower surface plate 6 on which a carrier 4 that revolves and rotates according to rotation, and a polishing pad 7 that can hold the workpiece 1 held by the carrier 4 are attached, and an upper surface plate A processing liquid supply unit (not shown) for supplying a processing liquid (polishing liquid) is provided between 5 and the lower surface plate 6.

By such a double-side polishing apparatus, during polishing, the workpiece 1 held by the carrier 4, that is, the glass substrate is sandwiched between the upper surface plate 5 and the lower surface plate 6, and the upper and

lower surface plates

5, 6 are polished. While supplying the polishing liquid containing the organic particles of the present invention as abrasive grains between the pad 7 and the workpiece 1, the carrier 4 rotates and revolves according to the rotation of the sun gear 2 and the internal gear 3. The upper and lower surfaces of the workpiece 1 are polished.

The applied load (processed surface pressure) is preferably in the range of 50 gf / cm ² or more and 200 gf / cm ² or less. When the said load is lower than 50 gf / cm < ² >, since the workability of a glass substrate falls, it is unpreferable. Moreover, when higher than 200 gf / cm < ² >, since processing will become unstable, it is unpreferable.
The surface roughness can be further reduced by polishing the main surface of the glass substrate with the processing surface pressure within the above range using the treatment liquid containing the abrasive grains of the organic particles of the present invention.

Conventionally, the mirror polishing process of the main surface of the glass substrate is a polishing process (first polishing process) for removing scratches and distortion remaining in the grinding process, while maintaining the flat surface obtained in this polishing process, Generally, it is performed through two steps of a finish polishing step (second polishing step) that finishes the surface roughness of the glass substrate main surface into a smooth mirror surface. In the present invention, after this finish polishing step, It is preferable to perform treatment (final finish polishing treatment) to which a treatment liquid using the organic particles of the present invention as abrasive grains is applied.

The conventional finish polishing step is usually performed using colloidal silica abrasive grains having an average particle diameter of about 10 to 40 nm. After this, a treatment liquid using the organic particles of the present invention as abrasive grains was applied. By performing the treatment (final finish polishing treatment), it is possible to further reduce the surface roughness. As described above, it is difficult to further reduce the surface roughness even if the final finish polishing is performed using colloidal silica abrasive grains that are finer or larger than the above particle size range.

As described above, after polishing the main surface of the glass substrate using a polishing liquid containing colloidal silica abrasive grains as polishing abrasive grains, the main surface of the glass substrate using a treatment liquid containing organic particles of the present invention as abrasive grains Is preferably mirror-polished. In other words, the main surface of the glass substrate having a work-affected layer is preferably subjected to mirror polishing using a treatment liquid containing the organic particles of the present invention as abrasive grains.

The roughness of the main surface of the glass substrate before the mirror polishing using the treatment liquid containing the organic particles of the present invention as abrasive grains is such that the arithmetic average roughness Ra is 0.3 nm or less, more preferably 0.2 nm. Is preferred. By doing so, it is possible to further reduce the substrate surface roughness by polishing treatment using the organic particles of the present invention as abrasive grains, for example, Ra can be finished to 0.2 nm or less, more preferably 0.1 nm or less. is there. When the roughness Ra of the main surface of the substrate before the polishing treatment with organic particles is larger than 0.3 nm, it may take a long time to sufficiently reduce the roughness. This is presumably because the hardness of the organic particles is lower than that of the glass substrate.

After the main surface of the glass substrate is mirror-polished using a treatment liquid containing organic particles as abrasive grains according to the present invention, cleaning is performed for the purpose of removing abrasive grains adhering to the glass substrate surface. It is preferable to clean the glass substrate with a system cleaner. The organic cleaning agent can dissolve (or swell) and remove organic particles that are abrasive grains, while having no etching or leaching action on glass. That is, since it is possible to perform cleaning by selecting a cleaning solution that does not have an etching action or a leaching action on the glass, it is possible to suppress an increase in the roughness of the glass substrate surface after the cleaning. Therefore, the ultra-low roughness (high smoothness) obtained by the mirror polishing process using organic particles as abrasive grains can be maintained as it is after cleaning. As a result, the surface roughness of the main surface of the glass substrate can be further reduced as compared with the current level, and thus a high-quality glass substrate can be produced.

As a cleaning agent suitable for the organic particles in the present invention, an organic cleaning agent such as an organic solvent or an amine compound is preferable.
Examples of the organic solvent include aromatic hydrocarbons such as toluene, xylene, and styrene, chlorinated aromatic hydrocarbons such as chlorobenzene and orthochlorobenzene, dichloromethane, trichloromethane, tetrachloromethane, and 1,2-dichloroethane. 1,1,1-trichloroethane, 1,1,2,2-tetrachloroethane, 1,2-dichloroethylene, trichloroethylene, tetrachloroethylene and other chlorinated aliphatic hydrocarbons, methanol, isopropyl alcohol, Alcohols such as 1-butanol, 2-butanol, isobutyl alcohol, isopentyl alcohol, methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, pentyl acetate, esters such as isopentyl acetate, ethyl ether, Ethers such as 1,4-dioxane and tetrahydrofuran Ketones such as acetone, methyl ethyl ketone, methyl butyl ketone, methyl isobutyl ketone, cellosolves such as cellosolve, methyl cellosolve, butyl cellosolve, cellosolve acetate, alicyclic hydrocarbons such as cyclohexanone, methylcyclohexanone, cyclohexanol, methylcyclohexanol, Examples thereof include aliphatic hydrocarbons such as normal hexane, cresol, carbon disulfide, N, N-dimethylformamide and the like.

Examples of the amine compound include ethylenediamine, diethylenetriamine, triethylenetetraamine, tetraethylenepentamine, pentaethylenehexamine, 2-[(2-aminoethyl) amino] ethanol, 2- [methyl [2- ( Dimethylamino) ethyl] amino] ethanol, 2,2 '-(ethylenebisimino) bisethanol, N- (2-hydroxyethyl) -N'-(2-aminoethyl) ethylenediamine, 2,2 '-(2- Aminoethylimino) diethanol, N1, N4-bis (hydroxyethyl) diethylenetriamine, N1, N7-bis (hydroxyethyl) diethylenetriamine, 1,3-diamino-2-propanol, piperazine, 1-methylpiperazine, 3- (1- Piperazinyl) -1-amine, 1- (2-aminoethyl) piperazine, 4-methylpiperazine-1-amine, 1-piperazinemethanamine, 4-ethyl-1-piperazine And 1-methyl-4- (2-aminoethyl) piperazine, 1- (2-hydroxyethyl) piperazine, and the like.

As a result of further examination of the organic cleaning agent as described above, the present inventor used a treatment liquid containing organic particles as abrasive grains, and after polishing the main surface of the glass substrate, the organic adhered to the glass substrate surface. It has been found that it is particularly suitable to use an organic solvent that can swell the particles or part thereof. Here, swelling is a phenomenon in which organic particles swell by absorbing an organic solvent. The part of the organic particles is excluded from a part of the organic particles formed, for example, when the organic particles are broken during the polishing process, or from the crosslinked body when the organic particles are crosslinked into a spherical shape. It means a part of organic particles adhering to the glass substrate surface.
Further, as a result of further investigations, the present inventor found that the ratio of the solubility parameter (SP value) of the organic solvent to the solubility parameter (SP value) of the monomer component of the resin constituting the organic particles is the detergency of the organic solvent. It has been found that it is preferable to select an organic solvent in which the ratio is within a specific range from the viewpoint of improving the detergency of organic particles.

Specifically, when the solubility parameter (SP value) of the monomer component of the resin constituting the organic particles is SP1, and the solubility parameter (SP value) of the organic solvent is SP2, SP2 / SP1 is 0.9 to 1.1. It is preferable to select an organic solvent that falls within the above range, and to perform a treatment in which the selected organic solvent is brought into contact with the glass substrate surface after the polishing treatment.

In other words, as a cleaning method after performing polishing processing (especially final finish polishing) using organic particles, processing using an organic solvent whose SP value is relatively close to the monomer component of the resin constituting the organic particles is optimal. is there. Since organic particles adhering to the substrate surface swell well by bringing the organic solvent having a relatively close SP value to the monomer component of the resin constituting the organic particles into contact with the substrate surface, a shift occurs at the interface with the substrate. Even organic particles (or a part thereof) firmly adhered to the substrate surface are easily peeled off from the substrate surface.
In addition, the solubility parameter (Solubility Parameter generally called “SP value”) can be calculated based on the chemical structural formula, and the SP value of typical substances can be found in “Science Chronology” etc. It is posted.

In addition, the present inventor also has a correlation with the detergency of the organic solvent with respect to the ratio of the molecular weight of the organic solvent to the molecular weight of the monomer component of the resin constituting the organic particles, and the ratio is within a specific range. It has been found that selecting an organic solvent is preferable from the viewpoint of improving the cleaning properties of organic particles.

Specifically, when the molecular weight of the monomer component of the resin constituting the organic particles is MW1 and the molecular weight of the organic solvent is MW2, the organic solvent is selected so that MW2 / MW1 is in the range of 0.5 to 1.5. In addition, it is preferable to perform a process of bringing the selected organic solvent into contact with the surface of the glass substrate after the polishing process.

Therefore, in the present invention, the above SP2 / SP1 is in the range of 0.9 to 1.1, and the above MW2 / MW1 is in the range of 0.5 to 1.5. Most preferably, an organic solvent is selected.
In addition, when the organic particle is a copolymer resin material containing a plurality of monomer components, an organic solvent that satisfies the above relationship can be selected for any of the monomer components.

In the present invention, it is preferable to use an aluminosilicate glass containing SiO ₂ as a main component and further containing alumina as the glass (glass type) constituting the glass substrate. A glass substrate using such glass can be finished to a smooth mirror surface by mirror polishing the surface, and the strength after processing is good. Further, the strength can be further increased by chemical strengthening.
The glass may be crystallized glass or amorphous glass. By using amorphous glass, the surface roughness of the main surface when the glass substrate is used can be further reduced.

As such an aluminosilicate glass, SiO ₂ is 58 wt% to 75 wt%, Al ₂ O ₃ is 5 wt% to 23 wt%, Li ₂ O is 3 wt% to 10 wt%, Na ₂ An aluminosilicate glass containing O as a main component in an amount of 4 wt% or more and 13 wt% or less (however, an aluminosilicate glass containing no phosphorus oxide) can be used. Further, for example, the alkaline earth metal oxide is 5% by weight or more, SiO ₂ is 62% by weight or more and 75% by weight or less, Al ₂ O ₃ is 5% by weight or more and 15% by weight or less, and Li ₂ O is added. 4% by weight or more and 10% by weight or less, Na ₂ O 4% by weight or more and 12% by weight or less, ZrO ₂ 5.5% by weight or more and 15% by weight or less as a main component, and Na ₂ O / ZrO ₂ An amorphous aluminosilicate glass containing no phosphorus oxide having a weight ratio of 0.5 to 2.0 and a weight ratio of Al ₂ O ₃ / ZrO ₂ of 0.4 to 2.5 can be obtained.

In addition, heat resistance may be required as a characteristic of a next-generation substrate (for example, a substrate used for a magnetic disk applied to a heat-assisted magnetic recording method). As the heat resistant glass in this case, for example, an alkaline earth metal oxide is 5% by weight or more, and the following is expressed in mol%, SiO ₂ is 50 to 75%, Al ₂ O ₃ is 0 to 6%, BaO 0-2%, Li ₂ O 0-3%, ZnO 0-5%, Na ₂ O and K ₂ O in total 3-15%, MgO, CaO, SrO and BaO in total 14 to 35%, ZrO ₂ , TiO ₂ , La ₂ O ₃ , Y ₂ O ₃ , Yb ₂ O ₃ , Ta ₂ O ₅ , Nb ₂ O ₅ and HfO ₂ in total 2 to 9%, A glass having a ratio [(MgO + CaO) / (MgO + CaO + SrO + BaO)] in the range of 0.85 to 1 and a molar ratio [Al ₂ O ₃ / (MgO + CaO)] in the range of 0 to 0.30 is preferably used. it can.

In the present invention, the surface of the glass substrate after the final finish polishing treatment using organic particles has an arithmetic average surface roughness Ra of 0.2 nm or less, more preferably 0.1 nm or less, and particularly preferably 0.06 nm or less. It is preferable to be a mirror surface. Furthermore, it is preferable that the mirror surface has a maximum peak height Rp of 2.0 nm or less, more preferably 1.0 nm or less. In the present invention, Ra and Rp refer to roughness based on Japanese Industrial Standard (JIS) B0601.
In the present invention, the surface roughness is practically the surface roughness obtained by measuring the range of 1 μm × 1 μm with a resolution of 256 × 256 pixels using an atomic force microscope (AFM). Preferred above.

In the present invention, for example, chemical strengthening treatment can be performed before or after the mirror polishing process. As a method of chemical strengthening treatment, for example, a low-temperature ion exchange method in which ion exchange is performed in a temperature range that does not exceed the temperature of the glass transition point, for example, a temperature of 300 degrees Celsius or more and 400 degrees Celsius or less is preferable. The chemical strengthening treatment is a process in which a molten chemical strengthening salt is brought into contact with a glass substrate, whereby an alkali metal element having a relatively large atomic radius in the chemical strengthening salt and a relatively small atomic radius in the glass substrate. This is a treatment in which an alkali metal element is ion-exchanged, an alkali metal element having a large ion radius is permeated into the surface layer of the glass substrate, and compressive stress is generated on the surface of the glass substrate. Since the chemically strengthened glass substrate is excellent in impact resistance, it is particularly preferable for mounting on a HDD for mobile use, for example. As the chemical strengthening salt, alkali metal nitric acid such as potassium nitrate or sodium nitrate can be preferably used.

As explained in detail above, the surface roughness of the main surface of the glass substrate is further reduced by reducing the surface roughness of the glass substrate by using, for example, mirror polishing of the glass substrate using the treatment liquid containing the organic particles of the present invention as abrasive grains. be able to. In other words, the treatment using the organic particles of the present invention is a treatment for reducing the roughness of the main surface of the glass substrate. And in this invention, the foreign particle adhesion defect of the glass substrate surface after a process can be reduced significantly by this organic particle being classify | determined predetermined.

That is, according to the present invention, the surface roughness of the main surface of the glass substrate can be further reduced compared to the current surface by processing the main surface of the glass substrate using a treatment liquid containing classified organic particles as abrasive grains. In addition, it is possible to manufacture a high-quality glass substrate for a magnetic disk that can greatly reduce foreign matter adhesion defects on the surface of the glass substrate.
As described above, the glass substrate for a magnetic disk manufactured by the present invention is suitable for a glass substrate used for a magnetic disk mounted on an HDD including a DFH type magnetic head capable of realizing an ultra-low flying height.

The present invention also provides a method for manufacturing a magnetic disk using the above glass substrate for a magnetic disk. The magnetic disk is manufactured by forming at least a magnetic layer (magnetic recording layer) on the glass substrate for magnetic disk according to the present invention. As a material for the magnetic layer, a hexagonal CoCrPt-based or CoPt-based ferromagnetic alloy having a large anisotropic magnetic field can be used. As a method of forming the magnetic layer, it is preferable to use a method of forming a magnetic layer on a glass substrate by a sputtering method, for example, a DC magnetron sputtering method.

Also, a protective layer and a lubricating layer may be formed in this order on the magnetic layer. As the protective layer, an amorphous hydrogenated carbon-based protective layer is suitable. For example, the protective layer can be formed by a plasma CVD method. Further, as the lubricating layer, a lubricant having a functional group at the end of the main chain of the perfluoropolyether compound can be used. The lubricating layer can be applied and formed by a dip method.

By using the glass substrate having ultra-smoothness and low surface defects obtained by the present invention, even when recording / reproducing is performed with a DFH head, problems such as recording / reproducing errors and head crashes do not occur and the reliability is high. A magnetic disk can be obtained. Therefore, it is suitable for manufacturing a magnetic disk with a higher recording density than ever before, for example, exceeding the next generation, for example, 750 gigabytes.

Hereinafter, embodiments of the present invention will be specifically described with reference to examples. In addition, this invention is not limited to a following example.
(Examples 1 to 3, Comparative Example 1)
The following (1) rough grinding step, (2) shape processing step, (3) fine grinding step, (4) end surface polishing step, (5) main surface polishing step, (6) chemical strengthening step, (7) main surface A glass substrate for a magnetic disk was manufactured through a final polishing step and (8) a main surface final final polishing step.

(1) Coarse grinding step First, a glass substrate made of disc-shaped aluminosilicate glass having a diameter of 66 mmφ and a thickness of 1.0 mm was obtained from molten glass by direct pressing using an upper die, a lower die, and a barrel die. In addition to such a direct press, a glass substrate may be obtained by cutting into a predetermined size from a plate glass manufactured by a downdraw method or a float method.

Next, a rough grinding process was performed on the glass substrate in order to improve dimensional accuracy and shape accuracy. This rough grinding process was performed using a double-side grinding machine.
(2) Shape processing step Next, a cylindrical grindstone is used to make a hole in the central portion of the glass substrate, and the outer peripheral end face is ground to a diameter of 65 mmφ. Chamfered.
(3) Precision grinding process This precision grinding process used the double-sided grinding apparatus.

(4) End surface grinding | polishing process Next, the end surface (inner periphery, outer periphery) of the glass substrate was grind | polished by brush grinding | polishing, rotating a glass substrate. And the surface of the glass substrate which finished the said end surface grinding | polishing was wash | cleaned.

(5) Main surface polishing step Next, the main surface polishing step was performed using a double-side polishing apparatus as shown in FIG. In a double-side polishing machine, a glass substrate held by a carrier is closely attached between an upper and lower polishing surface plate to which a polishing pad is attached, and this carrier is engaged with a sun gear (sun gear) and an internal gear (internal gear). The glass substrate is sandwiched between upper and lower surface plates. Thereafter, a polishing liquid is supplied and rotated between the polishing pad and the polishing surface of the glass substrate, whereby the glass substrate revolves while rotating on the surface plate to simultaneously polish both surfaces. Specifically, a polishing process was performed using a hard polisher (hard urethane foam) as a polisher. As the polishing liquid, cerium oxide was dispersed as an abrasive. The glass substrate after the polishing step was washed and dried.

(6) Chemical strengthening process Next, the glass substrate which finished the said washing | cleaning was chemically strengthened. For chemical strengthening, a chemical strengthening solution in which potassium nitrate and sodium nitrate were mixed was prepared, the chemical strengthening solution was heated to 380 ° C., and the cleaned and dried glass substrate was immersed for about 4 hours to perform chemical strengthening treatment.

(7) Main surface finish polishing step Next, using the same double-side polishing apparatus as used in the above main surface polishing step, the polisher was replaced with a polishing pad (foamed polyurethane) of a soft polisher (suede), and a finish polishing step was performed. . This finish polishing step is a mirror surface for finishing the surface roughness of the glass substrate main surface to a smooth mirror surface with a Ra of about 0.3 nm or less while maintaining the flat surface obtained in the first polishing step described above. Polishing process. As the polishing liquid, colloidal silica (particle diameter (D50): 18 nm) dispersed in water was adjusted to be acidic. The glass substrate after the finish polishing step was washed and dried.

(8) Main surface final finish polishing step: Polishing the abrasive particles adjusted to pH 2 to 10 by adding 1% by weight of organic particles made from PMMA resin (acrylic resin) with an average particle size of 19 μm (after classification) to water. A liquid was used. The organic particles are classified using a swirling airflow classifier so that the number of particles having a particle size of 3 μm or less contained in the organic particles is 5% or less in the number particle size distribution.
The polishing method was performed in the same manner as the above-described finish polishing step. The glass substrate after the final finish polishing step was washed and dried.
As a cleaning method after the final finish polishing, isopropyl alcohol having a water content of 1.0% by weight or less was used for the cleaning liquid, and cleaning was performed by applying ultrasonic waves while the glass substrate was immersed in the cleaning liquid.

The surface roughness (Ra) of the main surface of the glass substrate for magnetic disk after washing was measured with an atomic force microscope (AFM), and as a result, Ra was reduced to 0.1 nm or less. In addition, the number of foreign matter adhesion defects on the main surface of the glass substrate after cleaning was counted from an image in the range of 10 μm × 10 μm of AFM, and the results are shown in Table 1.

Also, the final finish polishing in the same manner as in Example 1 above, except that the abrasive grains used in the main surface final finish polishing step were changed to organic particles made from styrene resin having an average particle size of 19 μm (after classification), Washing was performed to obtain a glass substrate for magnetic disk (Example 2).
Further, the final finish polishing in the same manner as in Example 1 above, except that the abrasive grains used in the main surface final finish polishing step were changed to organic particles made from urethane resin having an average particle size of 19 μm (after classification). Washing was performed to obtain a glass substrate for magnetic disk (Example 3).
Note that the organic particles used in Examples 2 and 3 were both swirling air classifiers, and the number of particles having a particle size of 3 μm or less contained in the organic particles was 5 in the number particle size distribution. It is classified so that it becomes less than%.
As for the glass substrate for magnetic disk obtained in Example 2 and Example 3 as well, the surface roughness (Ra) of the main surface was measured with an atomic force microscope (AFM). As a result, Ra = 0.1 nm or less. It was reduced.

In addition, the final finish polishing and cleaning are performed in the same manner as in Example 1 except that the abrasive used in the main surface final finish polishing step is changed to organic particles made of PMMA resin having an average particle diameter of 19 μm as a raw material. A glass substrate for magnetic disk (Comparative Example 1) was obtained. In addition, the said organic particle used what was not classifying like Example 1. FIG. The number of particles having a particle size of 3 μm or less contained in the organic particles was about 10% in the number particle size distribution.

For the magnetic disk glass substrates obtained in Examples 2 and 3 and Comparative Example 1, the number of foreign matter adhesion defects on the main surface of the glass substrate after cleaning was counted in the same manner as described above. The results are summarized in Table 1 below.

As is clear from the results in Table 1 above, foreign matter adhesion on the surface of the glass substrate after the treatment is achieved by using as the abrasive grains classified so as to reduce the number of particles having a particle size of 3 μm or less contained in the organic particles. The number of defects can be greatly reduced.
The final finish polishing and cleaning were performed under the same conditions as in Comparative Example 1 except that the organic particles were changed to styrene resin and urethane resin, respectively, to obtain a glass substrate for magnetic disk (Comparative Examples 2 and 3). When evaluated in the same manner, the number of foreign matter adhesion defects was 23 and 25, respectively. That is, from the comparison between Examples 2 and 3 and Comparative Examples 2 and 3, it was found that even when the resin material was changed to styrene resin or urethane resin, the classification effect was obtained in the same manner as acrylic resin. .

(Examples 4 to 7)
Regarding the organic particles used in Example 1, the classification rate in the number particle size distribution of the number of particles having a particle size of 3 μm or less contained in the organic particles was variously changed as shown in Table 2.
Except that the abrasive grains used in the main surface final finish polishing step of Example 1 were changed to these organic particles, final finish polishing and cleaning were performed in the same manner as in Example 1 to obtain a glass substrate for a magnetic disk ( Examples 4 to 7) were obtained.
For the magnetic disk glass substrates obtained in Examples 4 to 7, the optical surface inspection apparatus OSA was used to count the number of foreign matter adhesion defects on the cleaned glass substrate main surface (the entire substrate surface). The results are summarized in Table 2 below.

As a result of variously changing the classification rate in the number particle size distribution of the number of particles having a particle size of 3 μm or less contained in the organic particles as shown in Table 2 above, the number of particles having a particle size of 3 μm or less contained in the organic particles is The number of foreign matter adhesion defects on the surface of the glass substrate after processing can be significantly reduced by using as the abrasive grains those classified so as to be 5% or less in the number particle size distribution. More preferably, it is 3% or less, and further preferably 2% or less.

Further, the final finish polishing and cleaning were performed under the same conditions as in Example 1 except that the average particle diameter of the organic particles was set to 5 μm, 10 μm, and 30 μm to obtain glass substrates for magnetic disks (Examples 8 and 9). , 10). The classification rate in the number particle size distribution of the number of particles having a particle size of 3 μm or less contained in these organic particles was 5% or less. When the number of foreign matter adhesion defects was evaluated in the same manner as in Example 1 for the obtained glass substrates of Examples 8, 9, and 10, they were 1, 0, and 0, respectively.

Further, the final finish polishing was performed under the same conditions as in Example 1 except that organic particles classified so that the number of particles having a particle size of 2 μm or less contained in the organic particles was 5% or less in the number particle size distribution were used. Then, a glass substrate for magnetic disk was obtained (Reference Example 1). Further, the final finish polishing is performed under the same conditions as in Example 1 except that organic particles classified so that the number of particles having a particle size of 1 μm or less contained in the organic particles is 5% or less in the number particle size distribution are used. The glass substrate for magnetic disk was obtained (Reference Example 2). When the number of foreign matter adhesion defects was evaluated in the same manner as in Example 1 for the glass substrates of Reference Examples 1 and 2, the foreign matter adhesion defects on the surface of the glass substrate after treatment were both improved slightly compared to Comparative Example 1. The number could not be reduced significantly. This is presumed to be because fine resin particles having a particle size of 3 μm or less that occupies most of the adhered foreign substances on the substrate surface and having a size exceeding 1 μm or 2 μm remain. In short, in order to greatly reduce the number of foreign matter adhesion defects on the glass substrate surface after the treatment, it is important to classify so that the number of particles having a particle size of 3 μm or less contained in the organic particles is reduced.

(Manufacture of magnetic disk)
The following film forming steps were applied to the magnetic disk glass substrates obtained in Example 1 to obtain magnetic disks for perpendicular magnetic recording.
That is, an adhesion layer made of a Ti-based alloy thin film, a soft magnetic layer made of a CoTaZr alloy thin film, an underlayer made of a Ru thin film, a perpendicular magnetic recording layer made of a CoCrPt alloy, a carbon protective layer, and a lubricating layer are sequentially formed on the glass substrate. A film was formed. The protective layer is for preventing the magnetic recording layer from deteriorating due to contact with the magnetic head, and is made of hydrogenated carbon, and provides wear resistance. The lubricating layer was formed by dipping a liquid lubricant of alcohol-modified perfluoropolyether.
As a result of performing a glide characteristic test on the obtained magnetic disk using a DFH head, a head crash did not occur and good results were obtained.

1 Glass substrate 2 Sun gear 3 Internal gear 4 Carrier 5 Upper surface plate 6 Lower surface plate 7 Polishing pad

Claims

A method of manufacturing a glass substrate for a magnetic disk,
Using a treatment liquid containing organic particles as abrasive grains, including processing to reduce the roughness of the main surface of the glass substrate,
The method for producing a glass substrate for a magnetic disk, wherein the organic particles are classified so as to reduce foreign matter adhesion defects on the surface of the glass substrate after the treatment.
2. The method for producing a glass substrate for a magnetic disk according to claim 1, wherein the glass particles are classified so as to reduce the number of particles having a particle size of 3 μm or less contained in the organic particles.
3. The glass substrate for a magnetic disk according to claim 2, wherein the number of particles having a particle size of 3 μm or less contained in the organic particles is classified so as to be 5% or less in the number particle size distribution. Method.
4. The method for producing a glass substrate for a magnetic disk according to claim 1, wherein the average particle diameter of the classified organic particles is in the range of 5 to 30 μm.
5. The method of manufacturing a glass substrate for a magnetic disk according to claim 1, wherein the organic particles are made of a styrene resin, an acrylic resin, or a urethane resin.
6. The method of manufacturing a glass substrate for a magnetic disk according to claim 1, wherein after the treatment, the glass substrate surface is subjected to a washing treatment under conditions such that the substrate surface roughness after washing does not increase. .
After polishing the main surface of the glass substrate using a polishing liquid containing silica abrasive grains as polishing abrasive grains, a treatment for reducing the roughness of the main surface of the glass substrate using a processing liquid containing the organic particles as abrasive grains. The method for producing a glass substrate for a magnetic disk according to claim 1, wherein the method is performed.
A method for producing a magnetic disk, comprising forming at least a magnetic recording layer on a glass substrate for a magnetic disk obtained by the production method according to claim 1.