JP2001250226A - Method for manufacturing substrate for information recording medium, and method for manufacturing information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a substrate for an information recording medium with the high smoothness, and a method for manufacturing the information recording medium using the substrate. SOLUTION: In the method for manufacturing the substrate for the information recording medium by a manufacturing process including a grinding process and a polishing process from substrate material, the grinding process is performed in the atmosphere, and the polishing process and the process after it are performed in a clean room.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a substrate for an information recording medium and a method for manufacturing an information recording medium, and more particularly to a method for manufacturing a substrate for an information recording medium such as a hard disk, an optical disk, and a magneto-optical disk. To a method for manufacturing an information recording medium.

[0002]

2. Description of the Related Art At present, disks are widely used as recording media such as hard disks and optical disks and substrates for such recording media. As the recording density of such a disk increases, it is required to ensure its surface smoothness.

A disc is generally manufactured through a shape processing step, a grinding step, a polishing step, and a final inspection step. The desired smoothness of the surface of the disk is achieved mainly by selecting the type and particle size of the polishing pad and abrasive grains used in the polishing step. However, the desired disk surface smoothness cannot be obtained only by the polishing conditions, and the environment in the manufacturing process has been regarded as a problem. For example, Japanese Unexamined Patent Application Publication No. 9-288820 discloses that a substrate is not exposed to the air until a film forming step performed after the final finish polishing, so that dust in the air does not adhere to the substrate. A method of manufacturing a substrate for a magnetic recording medium in which finish polishing is performed in a clean room having a predetermined degree of cleanness while rinsing with an aqueous solution using a polishing tape is described.

Japanese Patent Application Laid-Open No. Hei 10-194785 discloses that at least one of a cleaning step, a chemical strengthening step, a cleaning step of a chemical strengthening treatment liquid, a drying step, an inspection step, and a storing step after the final polishing step is made of glass. A method of manufacturing a glass substrate for an information recording medium performed in a clean room so that particles do not adhere to the substrate is described.

[0005]

All of these manufacturing methods have a problem of a manufacturing environment in a final polishing step and steps subsequent to the final polishing step. However, even if these measures are taken, there still remains a problem that a minute defect (a convex defect or a concave defect) occurs on the disk surface, and a substrate for an information recording medium applicable to high-density recording cannot be obtained. there were. As a result of investigating the cause, it was found that there was a cause in a manufacturing environment in a polishing process or the like before a final polishing process, which was not regarded as a problem until now. That is, hitherto, the double-side polishing apparatus used in the polishing step has been placed outside the clean room because of dust generation and the like, and the polishing step before the final polishing step has been performed in the air.

[0006] As a polishing liquid used in such a polishing step, a polishing liquid obtained by mixing polishing abrasive grains of cerium oxide or colloidal silica with tap water has been used. But,
Fine particles floating in the atmosphere (for example, aluminum, iron, lead, chromium, copper, etc.) and fine particles contained in tap water used in the polishing liquid (for example,
A disk case for copper, iron, lead, etc.) to intervene between the polishing pad and the disk to damage the disk surface, and to store and transport particles and disks adhering to the disk surface when transporting the disk May come into contact and scratch the surface of the disc. Further, it has been found that particles are left on the disk surface due to poor cleaning, and the particles are firmly attached to the disk by, for example, heat treatment in a chemical strengthening step to deteriorate smoothness.

[0007] Further, during each of the above manufacturing steps, the disk is conveyed in a disk case accommodating a plurality of disks. However, if a common disk case is used in all the steps, foreign substances adhering to the disk case in the previous step will be brought to the subsequent step, which will cause a deterioration in the smoothness of the disk. In particular, if a common disk case is used to transport the disk from the grinding process performed in the atmosphere where the smoothness of the disk surface does not matter to the polishing process performed in the clean room, even if the disk case is cleaned before the polishing process Even if it is processed, there is a possibility that foreign matter is brought in. The present invention has been made to solve the above-described problems, and has as its object to provide a method of manufacturing a substrate for an information recording medium having high smoothness and a method of manufacturing an information recording medium using the same.

[0008]

To achieve the above object, the present invention has the following arrangement. The invention of claim 1 is
In a method for manufacturing an information recording medium substrate in which an information recording medium substrate is manufactured by a manufacturing process including a grinding process and a polishing process from a substrate material, the grinding process is performed in the air, and the polishing process and subsequent processes are performed in a clean room. This is a method for manufacturing a substrate for an information recording medium.

The polishing step in the present invention aims at improving the smoothness of the substrate surface. In this step, the particles floating in the air are prevented from adhering to the substrate, and thus the polishing step is performed. The occurrence of scratches can be prevented. According to the present invention, it is possible to reduce the incidence of defects generated on the substrate surface, particularly, the occurrence of concave defects. In the present invention, the polishing step includes a main surface polishing step of polishing the main surface of the substrate and an end face polishing step of polishing the end face of the substrate.

According to a second aspect of the present invention, there is provided a method of manufacturing a substrate for an information recording medium, comprising the steps of grinding, shaping, polishing, chemically strengthening and inspecting a substrate material. This is a method for manufacturing a substrate for an information recording medium, in which a grinding step and a shape processing step are performed in the air, and a polishing step to an inspection step are performed in a clean room. According to the present invention, the polishing step, the chemical strengthening step, and the inspecting step are performed in a clean room, so that the concave defect generated in the polishing step, the convex defect caused by the attachment of foreign matter to the substrate in the chemical strengthening step, Can reduce the incidence of convex defects.

According to a third aspect of the present invention, there is provided a method for manufacturing an information recording medium substrate for manufacturing an information recording medium substrate from a substrate material by a process including a grinding step and a polishing step, wherein at least the polishing step is performed in a clean room. This is a method for manufacturing a medium substrate. ADVANTAGE OF THE INVENTION According to this invention, the incidence rate of the defect (concave defect or convex defect) which generate | occur | produces in a board | substrate surface can be reduced. In the present invention, steps other than the polishing step performed before the polishing step, for example, the grinding step and the shape processing step may be performed in a clean room. Further, as described above, the cleaning step after the final polishing step, the chemical strengthening step, the inspection step, and the packing step can be performed in a clean room. This case is preferable because the reliability is further improved.

According to a fourth aspect of the present invention, the cleanliness in the clean room is less than 100,000 in a class.
3. The method for manufacturing a substrate for an information recording medium according to claim 1. According to the present invention, it is possible to further reduce the incidence of defects (convex, concave) occurring on the disk surface. This cleanliness is defined as the number of particles greater than 0.5 μm present in a cubic foot atmosphere.
According to the present invention, the cleanliness of the clean room is class 5000.
It is preferably 0 or less, more preferably 10,000 or less.

According to a fifth aspect of the present invention, there is provided the information recording medium according to any one of the first to fourth aspects, wherein at least the polishing liquid used in the polishing step includes an abrasive and a liquid from which fine particles have been removed. This is a method for manufacturing a substrate. According to the present invention, by removing fine particles from the liquid contained in the solvent of the polishing liquid used in the polishing step, it is possible to reduce the incidence of defects generated on the disk surface in the polishing step, especially the occurrence of concave defects. it can.

As minute particles to be removed,
Examples thereof include those having high hardness which may damage the substrate surface in the polishing step, those having high adhesion to the substrate surface, and those which firmly adhere to the substrate surface by heat treatment or the like. The size of this particle is, for example, 1
μm or more, more preferably 0.5 μm or more, even more preferably 0.3 μm or more. Of course, it is needless to say that it is better to remove those having the above-mentioned size.

The method for removing minute particles from the liquid is not particularly limited, and examples thereof include filtration using a filter. In this case, the liquid may be circulated and a filter may be provided in a part of the circulation path, or the liquid that has passed through the filter may be prepared and subjected to polishing or the like in a batch system.

The liquid used for the polishing liquid is usually
Water is used. In this case, defects can be prevented by using functional water such as so-called pure water, ultrapure water, and deionized water / DI (Deionized Water). In particular, it is preferable to use ultrapure water in order to avoid the influence of impurities contained in water. Ultrapure water production methods include ultrafiltration membrane / UF (ultra filtration membrane) and reverse osmosis membrane / RO
(Reverse osmotic membrane).
It is most preferable to use water produced by a method using the method (hereinafter referred to as RO water). Further, as the liquid, a liquid containing hydrofluoric acid or silicic hydrofluoric acid having chemical corrosiveness to the substrate may be used.

The invention according to claim 6 is the method according to claim 5, wherein the fine particles contain any of copper, iron and lead. According to the present invention, even if tap water is used as a solution, a defect (particularly, a concave defect) is removed by removing a component which is usually contained in tap water and may cause a defect in the polishing step. ) Can be prevented.

The invention according to claim 7 is the information recording medium substrate according to any one of claims 3 to 6, wherein the information recording medium substrate is a glass substrate, and the manufacturing step includes a chemical strengthening step. It is a manufacturing method. Examples of the chemical strengthening step include low-temperature chemical strengthening in which ion exchange is performed in a region not exceeding a transition temperature from the viewpoint of a glass transition point. In this case, an alkali molten salt such as potassium nitrate or sodium nitrate used for chemical strengthening is heated to about 280 ° C. to 450 ° C.
This is performed by immersing the glass substrate in a solution heated to a certain degree.

Generally, a cleaning step is usually performed before the chemical strengthening treatment. However, foreign substances contained in the polishing liquid (solvent) in the polishing step of the glass substrate surface due to defective cleaning or the like can be removed. If the chemical strengthening is performed while the particles are adhered to the substrate surface without being adhered, the particles are firmly adhered to the glass substrate surface due to the heat of the chemical strengthening treatment liquid, and become a convex defect without being satisfactorily performed in the subsequent cleaning step. Therefore, at least the polishing step is performed in a clean room, and more preferably, the polishing liquid used in the polishing step includes an abrasive and a liquid from which fine particles have been removed, so that chemicals free from defects (concave defects and convex defects) can be obtained. A tempered glass substrate can be manufactured.

[0020] The invention of claim 8 provides that the cleanliness in the clean room in the chemical strengthening step is at least class 10000.
8. A method for manufacturing a substrate for an information recording medium according to claim 7, wherein: In the chemical strengthening step, if particles are attached to the substrate, the particles are firmly attached by heating and cannot be completely removed in a subsequent cleaning step, resulting in a defect. Therefore, the occurrence of defects can be prevented by performing the chemical strengthening step in a clean room.

According to a ninth aspect of the present invention, the cleanliness in the clean room is set for each of one or more of the grinding step, the shape processing step, the polishing step, the chemical strengthening step, and the inspection step. 9. The method for manufacturing a substrate for an information recording medium according to claim 1, wherein the cleanliness in the clean room is improved as a process unit advances. ADVANTAGE OF THE INVENTION According to this invention, since the cleanliness of a clean room can be improved as the smoothness of a board | substrate material increases, the board with high smoothness can be manufactured.

In the present invention, for example, the grinding step for improving the flatness and the shape accuracy of the substrate and the shape processing step for forming the end shape of the substrate are performed in the air, and the steps after the polishing step are performed. In a clean room, and the polishing step (including the end face polishing step and the main surface polishing step), the chemical strengthening step, and the inspection step are each performed in a single manufacturing environment, and are performed in a class 100,000, class 10,000, and class 1000 environment. Can be carried out. Further, when the polishing step is separated from the end face polishing step and the main surface polishing step to class 500000 and class 100000, respectively, or when the main surface polishing step is performed in a plurality of polishing steps, the cleanliness is further reduced for each polishing step. Can be set. As described above, the polishing step and the shape processing step may be performed in a clean room.

According to a tenth aspect of the present invention, there is provided a method for manufacturing a substrate for an information recording medium according to the ninth aspect, wherein a disk case for accommodating a substrate is different for each process unit. According to the present invention,
Particles used in the previous process and attached to the disk case are not brought to the next process, so that defects can be prevented. In this case, by bringing the disc case into a color indicating the environment in which the disc case is used, or by using different materials, it is possible to reliably prevent particles from being brought in from the previous process.

Hereinafter, a method of using a disk case in which a different color is colored for each process or atmosphere to be used will be described with reference to the manufacture of a hard disk substrate made of glass as an example. The manufacture of a glass substrate for a hard disk will be described as an example. The manufacture of glass substrates for hard disks
It can be roughly divided into a grinding process, a shape processing process, a polishing process, a chemical strengthening process, and an inspection process. Among these manufacturing steps, the grinding step and the shape processing step are performed in the air, and the steps from the polishing step to the inspection step are performed in a clean room. Therefore, the disk case used in the atmosphere is colored black, and the disk case used in the clean room is colored green.
A disk case colored black is used to transport the disk between the grinding step and the shape processing step, and a disk case colored green is used to transport the disk between the polishing step and the inspection step. I do. As a result, the disk case used in the atmosphere and the disk case used in the clean room are distinguished, and the disk case used in the grinding process and the shape processing process performed in the atmosphere undergoes a polishing process to an inspection process. Is prevented from being brought into a clean room. Therefore, since the inside of the clean room can be kept clean, it is possible to manufacture a disk having excellent smoothness.

A specific example of a disk case used for the above purpose will be described with reference to FIGS. The disk case 10 has a box-like shape with the upper and lower parts opened. Then, the disk 12 is inserted and removed from above the disk case. This disk case 10
Has a front wall 16 and a rear wall 18 facing each other, and a pair of side walls 20. A partition 21 is provided at the center of the disk case 10. The partition forms two rows of storage lanes 10a for storing the disks 12 in the disk case 10.

At a position facing each storage lane 10a of the front wall 16 and the rear wall 18, a substantially U-shaped notch 22 is provided.
Are formed. Front wall 16 of each storage lane 10a
Alternatively, the vicinity of the center of the disk 12 housed facing the rear wall 18 is exposed from the cutout.

At the upper end of the side wall 20, there is formed a flange portion 20d which protrudes outward to enable the disk case 10 to be held by a robot hand or the like. As shown in FIG. 2, the side wall 20 has an upper thin plate portion 20a, a tapered portion 20b whose thickness increases inward from the thin plate portion 20a downward, and a tapered portion 20a.
The thick plate portion 20c having the maximum thickness b is continuously formed. On both sides of the side wall 21, an upper flat portion 21a, a tapered portion 21b protruding inward from the flat portion to the lower side, and a protrusion formed continuously with the tapered portion 21b, corresponding to the side wall 20. It has a portion 21c.

By making the side wall 20 and the partition wall 21 face each other, the side wall 20 is located above the storage lane 10a.
In the portion where the tapered portion 20b is formed, the interval between the side wall 20 and the partition 21 gradually decreases downward, and the portion where the thick plate portion 20c and the protruding portion 21c face each other. In this case, the distance between the side wall 20 and the partition 21 is minimized. This makes it possible to stably hold the disk 20.

An opening 14 is formed between the lower end of the side wall 20 and the lower end of the partition 21. Inside of side wall 20 and partition 2
Ribs 24 for forming a groove for holding the disk 12 upright are provided on both sides of the disk 1. As shown in FIGS. 1 and 2, the rib 24 is formed from the thin plate portion 20 a and the flat portion 21 a of the outer wall 20 and the partition 21 to the lower ends of the tapered portions 20 b and 21 b. The partition 21 has a curved shape that protrudes inside the storage lane 10a in accordance with the shape of the tapered portions 20b and 21b.

As shown in FIGS. 3 and 4, the ribs 24 are arranged at intervals slightly larger than the thickness of the disk 12 to be stored.
A groove for holding the peripheral portion of the disk 12 is formed between the four. The rib 24 has a trapezoidal cross-sectional shape whose width decreases inward to enable the disk 12 to be easily inserted from above the storage lane 10a.

Below the front wall 16, the rear wall 18, the side wall 20, and the partition 21 of each storage lane 10a, there is formed a frame 26 shaped to fit above the storage lane 10a of the same disk case 10. . The bottom surface of the frame 26 is formed flat so that the disk case 10 can be transported by a roller conveyor or the like. When the disk 12 is immersed in a processing liquid to perform a chemical treatment on the disk 12, or when the disk 12 is washed while being stored in the disk case, the groove between the ribs 24 is used to discharge the liquid. A slit can be formed. As a result, the treatment liquid and the cleaning liquid do not stay in the groove after the completion of the chemical treatment and the cleaning.

Such a disk case 10 is formed of a material such as a metal, a resin, or the like that can withstand a use environment such as a processing solution used for processing the stored disk 12 and a processing temperature. In particular, from the viewpoint of manufacturing cost and finishing accuracy, it is preferable to integrally mold with resin. As such a resin, general resins such as various polyolefins such as polyethylene and polypropylene, polyvinyl chloride, and Teflon (registered trademark) (PTFE) can be used. In particular, when the disk case is manufactured by a normal injection molding method, the resin may be, for example, polycarbonate, polyamide, thermotropic liquid crystal polymer (LC).
P), polyetheretherketone (PEEK), polyetherketone (PEK), PEEK-based alloy resin [eg, PEEK / thermotropic liquid crystal polymer, PEE
K / polybenzimidazole (PBI), etc.], polybenzimidazole (PBI), polyphenylene sulfide (PPS), polyethersulfone (PES), polyetherimide (PEI), polytetrafluoroethylene (PTFE), etc. It is preferable to use such as.

In the eleventh aspect of the present invention, the surface roughness of the information recording medium substrate may be Rmax ≦ 3 nm, Ra ≦ 0.3 n
The method for manufacturing a substrate for an information recording medium according to any one of claims 1 to 10, wherein m is m. ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide a board | substrate with a high surface smoothness and without a defect (concave defect, convex defect). Further, the surface roughness of the information recording medium substrate is such that Rmax ≦ 2 nm and Ra ≦ 0.
Desirably, it is 2 nm.

A twelfth aspect of the present invention is a method for manufacturing an information recording medium for forming a recording layer on an information recording medium substrate obtained by the method for manufacturing an information recording medium substrate according to any one of the first to tenth aspects. According to the present invention, an information recording medium having a high recording density can be manufactured by using a substrate having a high surface smoothness.

This recording layer corresponds to a magnetic layer when the information recording medium is a magnetic disk (hard disk). As the magnetic layer, for example, CoPt containing Co as a main component, C
oCr, CoNi, CoNiCr, CoCrTa, Co
CrPt, CoNiPt, CoNiCrPt, CoCr
Magnetic thin films such as PtTa, CoCrPtB and the like can be mentioned.

Usually, a seed layer and a base layer are formed between the substrate and the magnetic layer. The seed layer has a function of suppressing variation in crystal grain size of the underlayer and the magnetic layer.
Materials such as Ti and CrNi are used. As the underlayer, a material such as a nonmagnetic metal such as Cr, Mo, Ta, Ti, W, V, B, and Al is used. When a material containing Co as a main component is used as the magnetic layer, it is preferable to use a Cr alloy as the underlayer for the purpose of improving magnetic properties.

A protective layer and a lubricating layer are usually formed on the magnetic layer. As the protective layer, for example, Cr, Cr alloy,
Examples thereof include carbon, zirconia, and silica. For the lubricating layer, a perfluoropolyether lubricant or the like is used.

The material of the substrate manufactured according to the present invention is not particularly limited. For example, a glass substrate (for example, a chemically strengthened glass substrate or a glass ceramic substrate), a ceramic substrate, an aluminum substrate, a carbon substrate, a silicon substrate, a plastic substrate, a polycarbonate substrate, and the like can be given.
The present invention has a remarkable effect particularly when the material of the substrate is a glass substrate (for example, a chemically strengthened glass substrate or a glass ceramic substrate (crystallized glass substrate)). For example, a glass ceramic substrate has a surface structure in which an amorphous phase and a crystalline phase are mixed on the substrate surface by subjecting the substrate to a crystallization process, but fine particles are present in the solvent used for the polishing liquid. If it is included, a concave defect called a pit in which only a crystal phase is missing is likely to occur. Therefore, by using a polishing liquid of a solvent from which minute particles have been removed, the occurrence of defects can be reduced.

[0039]

Hereinafter, embodiments of the present invention will be described.
The present invention is not limited to this. Example 1 In this example, a glass substrate for a magnetic disk (hard disk) was manufactured, and a magnetic disk was manufactured using this glass substrate. The method of the present embodiment
(1) rough lapping step (rough grinding step), (2) shape processing step, (3) fine lapping step (fine grinding step),
(4) mirror-finished end face process, (5) first polishing process, (6)
Second polishing step, (7) chemical strengthening step, (8) inspection step,
(9) Includes a magnetic disk manufacturing process.

In this embodiment, the steps from (1) rough lapping step to (3) fine lapping step are performed in the atmosphere.
(4) The process from the mirror finish processing to the (6) second polishing process is performed in the first clean environment, and (7) the chemical strengthening process is performed in the second clean environment.
In a clean environment, (8) the inspection process was performed in a third clean environment, and (9) the magnetic disk manufacturing process was performed in a fourth clean environment. Each clean environment has a cleanliness level of class 100000 (first clean environment), class 100
00 (second clean environment), class 1000 (third clean environment), class 100 (fourth clean environment)
The environment was such that the filtered air in the clean room was circulated.

As the water of the polishing liquid used in the polishing apparatus from the above (4) end surface mirror polishing step to (6) the second polishing step, RO water was used. In addition, for each manufacturing environment (first, second,
Differently colored disk cases were used as disk cases for storing disks (substrates) in clean environments (3, 4).

(1) Rough wrapping process First, a die using an upper mold, a lower mold, and a body mold from molten glass.
Circle with a diameter of 96mmφ and a thickness of 1.5mm
A glass substrate made of aluminosilicate glass
Obtained. In this case, besides direct press,
Grinding from sheet glass formed by the draw method or float method
A disk-shaped glass substrate may be obtained by cutting with a grinding stone.
As this aluminosilicate glass, SiO 2₂: 5
8 to 75% by weight, Al ₂O₃: 5 to 23% by weight, Li₂
O: 3 to 10% by weight, Na₂O: contains 4 to 13% by weight
Chemically strengthened glass was used.

Next, a lapping step was performed on the glass substrate to improve the dimensional accuracy and the shape accuracy. This lapping process uses a double-sided lapping device and has a particle size of # 400.
This was performed using abrasive grains of Specifically, first, the granularity #
By rotating the sun gear and the internal gear using 400 alumina abrasive grains and setting the load to about 100 kg, both surfaces of the glass substrate housed in the carrier have a surface accuracy of 0 to 1 μm and a surface roughness (Rmax) of 6 μm. Wrapped to the extent.

(2) Shape Processing Step Next, a hole is formed in the center of the glass substrate using a cylindrical grindstone, and the outer peripheral end surface is ground to reduce the diameter to 95 mm.
After the diameter was changed to φ, a predetermined chamfering process was performed on the outer peripheral end surface and the inner peripheral end surface. At this time, the surface roughness of the glass substrate end face is
Rmax was about 4 μm.

(3) Fine Lapping Step Next, the grain size of the abrasive grains is changed to # 1000, and the surface of the glass substrate is wrapped, so that the surface roughness is 2
μm, and Ra about 0.2 μm. The glass substrate after the lapping step was sequentially immersed in each of the cleaning tanks (ultrasonic application) of a neutral detergent and water to perform ultrasonic cleaning.

(4) End Mirror Finishing Step Then, the surface roughness of the end face (inner circumference and outer circumference) of the glass substrate is reduced by R, while rotating the glass substrate by brush polishing.
Polishing was performed to a maximum of 1 μm and a Ra of about 0.3 μm. Then, the surface of the glass substrate which had been subjected to the end surface mirror finishing was washed with water.

(5) First Polishing Step Next, a first polishing step was performed using a double-side polishing apparatus in order to remove scratches and distortion remaining in the above-described lapping step. In the double-side polishing apparatus, a glass substrate held by a carrier is brought into close contact between an upper and lower plate to which a polishing pad is attached, and this carrier is meshed with a sun gear and an internal gear, and the glass substrate is pinched by an upper and lower standard. . Thereafter, by supplying a polishing liquid between the polishing pad and the polishing surface of the glass substrate and rotating the glass substrate, the glass substrate revolves while rotating on the surface plate, and both surfaces are simultaneously polished. Hereinafter, the same apparatus was used as the double-side polishing apparatus used in the examples.

More specifically, a polishing step was performed using a hard polisher (hard urethane foam) as the polisher. Polishing conditions were as follows: cerium oxide (average particle diameter 1.3
μm) + RO water, load: 100 g / cm ² , polishing time: 15 minutes. The glass substrate having been subjected to the first polishing step was sequentially immersed in cleaning tanks of a neutral detergent, pure water, pure water, IPA and IPA (steam drying), ultrasonically cleaned, and dried.

(6) Second Polishing Step Next, a second polishing step was performed using a double-side polishing apparatus of the same type as that used in the first polishing step, changing the polisher to a soft polisher (suede pad). In the second polishing step, while maintaining the flat surface obtained in the above-described first polishing step, for example, the surface roughness Ra is set to 1.0 to 0.3 μm.
It is intended to reduce it to about m or less. The polishing conditions were as follows: cerium oxide (average particle size 0.8 μm) + RO water as a polishing solution, load: 100 g / cm ² ,
The polishing time was 5 minutes. The glass substrate having been subjected to the second polishing step was sequentially immersed in cleaning tanks of a neutral detergent, pure water, pure water, IPA, and IPA (steam drying), ultrasonically cleaned, and dried.

(7) Chemical Strengthening Step Next, the glass substrate after the above cleaning was chemically strengthened. For the chemical strengthening, a chemical strengthening solution prepared by mixing potassium nitrate and sodium nitrate was prepared, this chemical strengthening solution was heated to 380 ° C., and the washed and dried glass substrate was immersed for about 4 hours to perform a chemical strengthening treatment. Sulfuric acid, neutral detergent, pure water, pure water, IPA, IPA
(Steam drying), immersed sequentially in each washing tank, ultrasonically washed, and dried.

(8) Inspection Step Next, a visual inspection of the surface of the glass substrate after the cleaning and a precision inspection utilizing reflection, scattering, and transmission of light were performed.
As a result, no defects such as protrusions and scratches were found on the surface of the glass substrate. This prevents particles floating in the atmosphere, which causes deterioration of the surface smoothness, from adhering to the substrate during the polishing process, and prevents the surface of the substrate from being damaged by particles interposed between the polishing pad and the substrate. Defects generated on the substrate surface due to particles interposed between the polishing pad and the substrate (particularly concave defects: rolling scratches) due to the fact that generation was prevented and particles contained in the solvent (liquid) of the polishing liquid were removed. It is considered that the above was prevented. In addition, it is thought that the defects in the chemical strengthening process (convex defects: iron contamination etc.) and the defects attached in the inspection process (convex defects) could be prevented by implementing them in a clean atmosphere in a clean room. Can be As described above, by performing the steps after the polishing step (specifically, the polishing step, the chemical strengthening step, and the inspection step) in a clean room, it is possible to prevent defects (concave defects, convex defects) occurring on the substrate surface. Can be.

The surface roughness of the main surface of the glass substrate obtained through the above steps was measured by an atomic force microscope (AFM). Rmax = 2.13 nm, Ra = 0.2
A glass substrate for a magnetic disk having an ultra-smooth surface of 0 nm was obtained.

(9) Magnetic Disk Manufacturing Process On both main surfaces of the magnetic disk glass substrate obtained through the above process, using an in-line sputtering device,
A NiA seed layer, a CrV underlayer, a CoPtCrB magnetic layer, and a hydrogenated carbon protective layer were sequentially formed, and a perfluoropolyether lubricating layer was formed by dipping to obtain a magnetic disk. About the obtained magnetic disk,
When a touch-down height test was performed, the touch-down height showed a good value of 5 nm. Further, the head did not crash even after the load / unload test (100,000 times).

Example 2 Instead of the aluminosilicate glass in Example 1, SiO ₂ : 35 to 65 mol%, Al ₂ O ₃ : 5 to 25 mol%, MgO: 10 to 40
_Mol%, TiO 2: _{5~15 mol%, Y} 2 O 3: _0~1
0 mol%, ZrO ₂ : 0 to 6 mol%, R ₂ O: 0 to 5 mol% (however, R represents at least one selected from the group consisting of Li, Na, and K), RO: 0 to 5 Mol% (where R represents at least one selected from the group consisting of Ca, Sr, and Ba), As ₂ O ₃ + Sb ₂ O ₃ : 0 to 2
Mol%, SiO ₂ + Al ₂ O ₃ + MgO + TiO ₂ : 9
Crystals of 2 mol% or more were crystallized, and a crystallized glass substrate whose main crystal was enstatite and / or a solid solution thereof was used. The manufacturing process of the glass substrate for the magnetic disk includes (1) a disc-shaped glass substrate material manufacturing process, and (2)
Crystallized glass manufacturing process, (3) shape processing step, (4) lapping step (grinding step), (5) mirror-surface processing step,
It comprises (6) a first polishing step, (7) a second polishing step, (8) an inspection step, and (9) a magnetic disk manufacturing step. Example 1
The difference is that the process was performed in a different clean environment for each process. Specifically, the above (1) disc-shaped glass substrate material manufacturing process to (4) lapping process are performed in the air, (5) the end surface mirror polishing process is performed in a first clean environment, and (6) the first The polishing process is performed in a second clean environment, (7) the second polishing process is performed in a third clean environment, (8) the inspection process is performed in a fourth clean environment, and (9) the magnetic disk manufacturing process is performed in a fifth clean environment. Conducted in an environment. Each clean environment has a cleanliness of class 50000
0 (first clean environment), class 100000 (second clean environment), class 50000 (third clean environment), class 1000 (fourth clean environment), class 1
00 (fifth clean environment), and the filtered air in the clean room was circulated. In addition, RO water was used as water for the polishing liquid used in the polishing apparatus from the above (4) end surface mirror polishing step to (6) the second polishing step.

(1) Disk-shaped glass substrate manufacturing process First, a die using an upper mold, a lower mold and a body mold from molten glass.
By the press press, the diameter of 66mmφ, pressure 1.3mm
A disk-shaped glass substrate was obtained. As this glass, Si
O₂: 35 to 65 mol%, Al₂O₃: 5 to 25 mol
%, MgO: 10 to 40 mol%, TiO₂: 5 to 15 mo
%, Y₂O₃: 0 to 10 mol%, ZrO ₂: 0-6 mo
%, R₂O: 0 to 5 mol% (where R is Li, Na,
K represents at least one member selected from the group consisting of
O: 0 to 5 mol% (where R is Ca, Sr, Ba)
Represents at least one member selected from the group consisting of
₂O₃, Sb₂O₃: 0 to 2 mol%, SiO₂+ Al₂
O₃+ MgO + TiO₂: Use at least 92 mol%
did.

(2) Step of Producing Crystallized Glass The thickness and flatness of the above glass substrate were adjusted by a double-sided lapping apparatus having an abrasive grain size of # 400. Thereafter, the glass plate is heat-treated at 750 ° C. for about 4 hours to form a crystal nucleus, and then maintained at a crystallization temperature of about 1000 ° C. for about 4 hours, so that the main crystal phase is enstatite and a solid solution thereof. A glass substrate was produced.
According to electron microscope observation, the average particle size of the crystal particles was 28
nm.

(3) Shape processing step The above crystallized glass substrate is wrapped by a double-sided lapping device to remove the warpage of the glass substrate.
A glass substrate was obtained by grinding with a relatively coarse diamond grindstone to form a diameter of 65 mmφ and a thickness of 0.7 mm. Both sides of this glass substrate are ground with a fine-grained diamond grindstone, a hole is made in the center of the glass substrate using a cylindrical grindstone, and the outer peripheral end surface is ground. Chamfered.

(4) Lapping Step A glass substrate is held by a carrier on an upper and lower platen to which a pellet on which diamond abrasive grains of a predetermined particle size are fixed is attached.
The upper and lower platens were rotated while supplying lubricating oil (coolant) to grind both surfaces of the glass substrate. The glass substrate after the above-mentioned grinding step was sequentially immersed in each of the cleaning tanks of a neutral detergent and pure water and subjected to ultrasonic cleaning. Then, the surface roughness of the end face (inner circumference, outer circumference) of the glass substrate is set to 1 μm for Rmax and 0.3 μm for Ra while rotating the glass substrate by brush polishing.
m. The surface of the glass substrate that had been subjected to the end surface mirror finishing was washed with water.

(5) First Polishing Step Next, the first polishing step was performed using a double-side polishing apparatus.
Specifically, a polishing step was performed using a hard polisher (hard foamed urethane) as the polisher. The polishing conditions were cerium oxide (average particle size: 1.3 μm) + RO water as the polishing liquid, load: 120 g / cm ² , and polishing time: 60 minutes. The glass substrate having been subjected to the first polishing step was sequentially immersed in cleaning tanks of a neutral detergent, pure water, pure water, IPA, and IPA (steam drying), ultrasonically cleaned, and dried.

(6) Second Polishing Step Next, a second polishing step was carried out using a double-side polishing apparatus of the same type as that used in the first polishing step, changing the polisher to a soft polisher (swade pad). The polishing conditions were as follows: colloidal silica (average particle size 0.1 μm)
m) Using + RO water, the load was 120 g / cm ² , and the polishing time was 20 minutes. The glass substrate having been subjected to the second polishing step was sequentially immersed in cleaning tanks of a neutral detergent, pure water, pure water, IPA, and IPA (steam drying), ultrasonically cleaned, and dried.

(7) Inspection Step Next, a visual inspection and a microscopic inspection of the surface of the glass substrate after the cleaning were performed. As a result, no defects such as protrusions and scratches were found on the surface of the glass substrate.

This prevents particles floating in an atmosphere that causes deterioration of the surface smoothness from adhering to the substrate during the polishing process, and prevents the particles from intervening between the polishing pad and the substrate. Defects generated on the substrate surface due to particles interposed between the polishing pad and the substrate (especially concave portions) due to the fact that the generation of surface scratches was prevented and the particles contained in the solvent (liquid) of the polishing liquid were removed. Defects: pits caused by rolling scratches and dropping out of the crystal phase are considered to be prevented. Also, it is considered that the defect (convex defect) attached in the inspection process could be prevented by performing the test in a clean atmosphere in a clean room. As described above, by performing the steps after the polishing step (specifically, the polishing step and the inspection step) in a clean room, defects (concave defects, convex defects) occurring on the substrate surface can be prevented.

When the surface roughness of the main surface of the glass substrate obtained through the above steps was measured by an atomic force microscope (AFM), Rmax = 3.23 nm and Ra = 0.3.
A glass substrate for a magnetic disk having an ultra-smooth surface of 1 nm was obtained.

(8) Magnetic Disk Manufacturing Process On both main surfaces of the glass substrate for a magnetic disk obtained through the above process, using an in-line type sputtering apparatus,
A NiAl seed layer, a CrV underlayer, a CoPtCrB magnetic layer, and a hydrogenated carbon protective layer were sequentially formed, and a perfluoropolyether lubricating layer was formed by dipping to obtain a magnetic disk. About the obtained magnetic disk,
When a touchdown height experiment was performed, the touchdown height showed a good value of 7 nm. Further, the head did not crash even after the load / unload test (100,000 times).

[Embodiment 3] Next, the second embodiment of the first embodiment
A glass substrate for a magnetic disk and a magnetic disk were manufactured in the same manner as in Example 1, except that the following third polishing step was performed after the polishing step. In this third polishing step, the first,
2 Using a double-side polishing machine of the same type as that used in the polishing step, changing the polisher to an ultra-soft polisher (suede pad), the polishing conditions were as follows: the polishing liquid was colloidal silica (average particle size 0.1 μm) + RO water; Load: 100g
/ Cm ² , and the polishing time was 3 minutes. The glass substrate after the third polishing step was sequentially immersed in each of the washing tanks of alkali, neutral detergent, neutral detergent, pure water, pure water, IPA, and IPA (steam drying), and was ultrasonically washed and dried. .

A visual inspection of the surface of the glass substrate after the cleaning and a precision inspection utilizing reflection, scattering, and transmission of light were performed. As a result, no defects such as protrusions and scratches due to deposits were found on the glass substrate surface. This is the first embodiment
In the same manner as in the above, it prevents particles floating in the atmosphere that causes deterioration of the surface smoothness from adhering to the substrate during the polishing process, and scratches the substrate surface due to particles interposed between the polishing pad and the substrate. Defects generated on the substrate surface due to particles interposed between the polishing pad and the substrate (particularly, concave defects) due to the prevention of the generation of particles and the removal of particles contained in the solvent (liquid) of the polishing liquid. : Rolling scratch) could be prevented. In addition, defects in the chemical strengthening process (convex defects: iron contamination, etc.) and defects attached in the inspection process (convex defects) could be prevented by implementing them in a clean atmosphere in a clean room. Conceivable. As described above, defects (concave defects, convex defects) generated on the substrate surface by performing the steps after the polishing step (specifically, the polishing step, the chemical strengthening step, and the inspection step) in a clean room.
Can be prevented.

The surface roughness of the main surface of the glass substrate obtained through the above steps was measured with an atomic force microscope (AFM). Rmax = 1.53 nm, Ra = 0.13
A glass substrate for a magnetic disk having a super smooth surface of 5 nm was obtained. When a touchdown height test was performed on the magnetic disk, the touchdown height was 4n.
m and a good value. Further, the head did not crash even after the load / unload test (100,000 times).

[Comparative Examples 1 to 3] As Comparative Example 1, in Example 1 described above, the end face mirror polishing step and the polishing step (first,
2 polishing step) and the chemical strengthening step were performed in the atmosphere without being performed in a clean room, and the solvent used in the polishing step was changed from RO water to tap water. A magnetic disk was manufactured.

As Comparative Example 2, in Example 2, the end face mirror polishing step and the polishing step (first and second polishing steps) were performed in the atmosphere without performing in a clean room, and the solvent used in the polishing step was RO water. A glass substrate for a magnetic disk and a magnetic disk were produced in the same manner as in Example 2 except that tap water was used.

As Comparative Example 3, in Example 3, the end face mirror polishing step, the polishing step (first, second, and third polishing steps) and the chemical strengthening step were performed in the air without being performed in the clean room. A glass substrate for a magnetic disk and a magnetic disk were produced in the same manner as in Example 3 except that the solvent used was changed from RO water to tap water. In Comparative Examples 1 to 3, in the inspection process, a visual inspection of the surface of the glass substrate, a precision inspection using a microscope, and the like were performed.

As a result, in Comparative Examples 1 and 3, protrusions caused by poor cleaning of particles in tap water or the atmosphere during the polishing step, convex defects due to protrusions firmly attached to the glass substrate during the chemical strengthening step, polishing defects, etc. Scratches of about 2 to 5 μm, which were thought to be rolling scratches formed during the process, were found. Further, in Comparative Example 2, a protrusion formed due to poor cleaning of tap water or particles in the atmosphere during the polishing step, or a protrusion formed during the polishing step, 2 to 5
Rolling flaws of about μm and concave defects of pits due to the drop of the crystal phase due to foreign matter were found.

The surface roughness of the main surface of the glass substrate obtained through the above-mentioned steps was measured by an atomic force microscope (AFM). Is about 7 to 10 nm, Ra is about 0.6 to
It became coarse at 0.9 nm. When a touchdown height test was performed on the obtained magnetic disk, the result was that the touchdown height was 15 nm or more.
A head crash occurred in the load / unload test (100,000 times).

[Evaluation] The above Examples 1 to 3 and Comparative Examples 1 to
3. The magnetic disk glass substrate and magnetic disk of Example 3, and the magnetic disk glass substrate and magnetic disk obtained when the solvent of the polishing liquid used in the polishing step in Examples 1 to 3 was changed to water (tap water). Were produced, and the occurrence rate of defects and the breakdown thereof were examined.
Table 1 shows the results. In Table 1, ○ in the clean room and RO water indicates that the test was performed, and X indicates that the test was not performed. In addition, the concave defect represents a rolling scratch due to a foreign substance of 2 to 5 μm,
The convex defect indicates a defect due to the attachment of foreign matter.

[0074]

[Table 1]

In Examples 1 to 3, the occurrence rate of rolling scratches (concave defects) was reduced by performing the polishing step and the subsequent steps in a clean room and changing the solvent (liquid) of the polishing liquid in the polishing step to RO water. It is 0%. The occurrence rate of convex defects is 1
The percentage is considered to be due to the crystallized glass substrate in Example 2 and to the cleaning failure in Example 3 due to one additional polishing step.

In Examples 4 to 6, water (tap water) was used as the solvent of the polishing liquid in the polishing step, so that foreign substances such as copper, iron and lead contained in the tap water were contained in the polishing liquid. Thus, it is considered that the occurrence rate of concave defects has become more than ten percent due to the foreign matter damaging the substrate surface during the polishing step. Particularly, in the sixth embodiment, the yield is lower than that of the fourth embodiment in a manufacturing process that requires an ultra-smooth glass substrate having a surface roughness of Rmax ≦ 2 nm and Ra ≦ 2 nm. In Example 5, since the surface of the crystallized glass substrate had a structure of an amorphous phase and a crystalline phase, the crystal phase portion was easily dropped off by foreign matter, and a slight concave defect was generated due to the material of the glass substrate. It is considered that the rate has increased. Also, the convex defect is
It is considered that foreign matters contained in the tap water remained as poor cleaning in the polishing liquid.

In Comparative Examples 1 to 3, polishing was not performed in a clean room, and the solvent of the polishing solution in the polishing process was changed to tap water, so that polishing by particles in the atmosphere and foreign matter in the polishing solution was performed. It can be seen that the rate of occurrence of rolling scratches (concave defects) during the process is as high as 20 to 30%. In particular, when a step of forming an ultra-smooth substrate surface (third polishing step) is added (Comparative Example 3),
It is as high as 33%. Further, the occurrence rate of concave defects is as high as 36% depending on the material of the crystallized glass substrate (Comparative Example 2). In addition, as for the convex defect, foreign matter adheres to the substrate surface due to, for example, the fact that the polishing step and the chemical strengthening step were not performed in a clean room and that cleaning water was used in the polishing step, and the like. In the case of a chemically strengthened glass substrate (Comparative Examples 1 and 3), the incidence is 10% or more. Note that the crystallized glass substrate is several percent lower than that of the chemically strengthened glass substrate because no chemical strengthening step is performed and no convex defect is generated due to foreign matter adhering to the substrate (Comparative Example 2). .

As can be seen from the above results, the polishing step and the subsequent steps are performed in a clean room, and the solvent (liquid) of the polishing liquid used in the polishing step is RO water, so that concave defects and convex defects can be eliminated. It can be seen that the incidence rate is almost 0% and the production yield is good. In addition, when tap water was used as the solvent of the polishing liquid, the production yield was 79% to 88%, which was about 10 to 20% lower than the above. Therefore, after the polishing step is performed in a clean room, and,
It turns out that it is best to use a solvent (for example, RO water) from which fine particles have been removed as the solvent of the polishing liquid used in the polishing step. In particular, the present invention relates to Rmax ≦ 2n
It can be said that it is particularly effective when a glass substrate having a super smoothness of m, Ra ≦ 0.2 nm is manufactured and the material of the glass substrate is a crystallized glass substrate.

The present invention is not limited to the embodiments described above, but can be implemented with appropriate modifications. For example, the lapping step and the shape processing step before the polishing step may be performed in a clean room. Further, in the above-described embodiment, the load / unload magnetic disk and the magnetic disk substrate have been described.
The present invention can be applied to an SS (contact start / stop) type magnetic disk and a magnetic disk substrate. The present invention is not limited to a magnetic disk and a substrate for a magnetic disk, but is applied to a general information recording medium and a substrate for an information recording medium such as a magneto-optical disk and a substrate for a magneto-optical disk for recording and reproducing with a head slider equipped with an optical pickup lens. it can.

[0080]

As is apparent from the above description, according to the present invention, in the manufacturing process of the information recording medium substrate, the processes after the polishing process are performed in a clean room. Particles floating inside can be prevented from adhering to the substrate material,
An information recording medium substrate having excellent smoothness can be manufactured. Further, since an information recording medium is manufactured using such an information recording medium substrate, an information recording medium having a high recording density can be manufactured.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a disk case used in a method for manufacturing an information recording medium substrate according to the present invention.

FIG. 2 is a front view showing a disk case used in the method of manufacturing an information recording medium substrate according to the present invention.

FIG. 3 is a plan view showing a disk case used in the method for manufacturing a substrate for an information recording medium of the present invention.

FIG. 4 is an enlarged plan view showing ribs of a disk case used in the method for manufacturing an information recording medium substrate of the present invention.

[Explanation of symbols]

 10 disc case 12 disc

Claims (12)

[Claims] An information recording medium substrate manufacturing method for manufacturing an information recording medium substrate from a substrate material by a manufacturing process including a grinding step and a polishing step, wherein the grinding step is performed in the atmosphere, and the polishing step and the subsequent steps are performed. A method for manufacturing a substrate for an information recording medium, wherein the process is performed in a clean room. 2. A grinding process, a shape processing process,
In a method for manufacturing a substrate for an information recording medium through a process including a polishing step, a chemical strengthening step, and an inspection step, the grinding step and the shape processing step are performed in the air, and the steps from the polishing step to the inspection step are performed. A method for producing an information recording medium substrate in a clean room. 3. A method for manufacturing an information recording medium substrate, comprising manufacturing a substrate for an information recording medium from a substrate material by a process including a grinding step and a polishing step, wherein at least the polishing step is performed in a clean room. Method. 4. The method for manufacturing a substrate for an information recording medium according to claim 1, wherein the cleanliness in the clean room is less than or equal to 100,000. 5. The method for manufacturing a substrate for an information recording medium according to claim 1, wherein at least the polishing liquid used in the polishing step includes a polishing agent and a liquid from which fine particles have been removed. 6. The method for manufacturing an information recording medium substrate according to claim 5, wherein the fine particles include any of copper, iron and lead. 7. The information recording medium substrate is a glass substrate, and the manufacturing process includes a chemical strengthening process.
7. The method for manufacturing a substrate for an information recording medium according to claim 6. 8. The method for manufacturing a substrate for an information recording medium according to claim 7, wherein at least the cleanliness in a clean room in the chemical strengthening step is set to class 10000 or less. 9. The cleanliness in the clean room is set for each of one or more of a grinding process, a shape processing process, a polishing process, a chemical strengthening process, and an inspection process, and as the process unit progresses, The method for producing a substrate for an information recording medium according to any one of claims 1 to 8, wherein the cleanliness in a clean room is improved. 10. The method of manufacturing a substrate for an information recording medium according to claim 9, wherein a disk case for accommodating the substrate material is different for each process unit. 11. The method of manufacturing an information recording medium substrate according to claim 1, wherein the surface roughness of the information recording medium substrate is Rmax ≦ 3 nm and Ra ≦ 0.3 nm. 12. A method for manufacturing an information recording medium, wherein a recording layer is formed on an information recording medium substrate obtained by the method for manufacturing an information recording medium substrate according to claim 1.