WO2015002152A1

WO2015002152A1 - Carrier, method for producing substrate for magnetic disks, and method for producing magnetic disk

Info

Publication number: WO2015002152A1
Application number: PCT/JP2014/067448
Authority: WO
Inventors: 将徳玉置
Original assignee: Hoya株式会社
Priority date: 2013-06-30
Filing date: 2014-06-30
Publication date: 2015-01-08
Also published as: MY170789A; JP6063044B2; SG11201509844VA; CN105163908A; CN105163908B; JPWO2015002152A1

Abstract

The present invention provides a carrier which is used for processing of a substrate for magnetic disks having good durability, and which is capable of reducing the occurrence of scratches or the like during the processing. A carrier according to the present invention is a carrier for holding a disk-shaped substrate in a horizontal position when a processing surface of a lapping plate is pressed against a main surface of the substrate and the main surface of the substrate is processed by relatively moving the substrate and the processing surface of the lapping plate. This carrier is formed using a composite material that contains glass fibers and a resin material, and is provided with a hold hole for holding the disk-shaped substrate. The inner circumferential wall surface of the hold hole is provided with a plurality of recesses in which no stretched glass fibers are present in the in-plane direction of the carrier, and the plurality of recesses are filled with a resin.

Description

Carrier, magnetic disk substrate manufacturing method, and magnetic disk manufacturing method

The present invention relates to a glass substrate for a magnetic disk mounted on a magnetic recording device such as a hard disk drive (hereinafter abbreviated as “HDD”) or a carrier used for manufacturing an aluminum alloy substrate having a NiP film formed on the surface. The present invention also relates to a method for manufacturing a magnetic disk substrate using the carrier, 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.

A glass substrate for a magnetic disk is usually manufactured through a rough grinding process, a shape processing process, a fine grinding process, an end surface polishing process, a main surface polishing process (first polishing process, second polishing process), a chemical strengthening process, and the like. The

In the main surface polishing step, for example, the glass substrate and the polishing pad are brought into contact with each other, and the polishing pad and the glass substrate are relatively moved while supplying the polishing liquid containing the polishing abrasive grains. Polish in a mirror shape. In this polishing step, for example, a planetary gear type double-side polishing apparatus as shown in FIG. 5 is generally used. The double-side polishing apparatus shown in FIG. 5 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 10 that revolves and rotates according to rotation, and a polishing pad 7 that can hold the workpiece 1 held on the carrier 10 are attached, and an upper surface plate A polishing liquid supply unit (not shown) for supplying a polishing liquid is provided between 5 and the lower surface plate 6.

With such a double-side polishing apparatus, the workpiece 1 held on the carrier 10, that is, the glass substrate is sandwiched between the upper surface plate 5 and the lower surface plate 6 during polishing, and the upper and

lower surface plates

5 and 6 are polished. While supplying the polishing liquid between the pad 7 and the workpiece 1, the carrier 10 revolves and rotates according to the rotation of the sun gear 2 and the internal gear 3, and the upper and lower surfaces of the workpiece 1 are moved. Polished.
Also in the grinding step, processing is performed using a double-side grinding apparatus having the same configuration as the double-side polishing apparatus.

As described above, the carrier holds the glass substrate when grinding or polishing the glass substrate, which is a workpiece, and is formed of, for example, a resin material. As shown in FIG. A whole holding member 11 having a plurality of holding holes 12 for holding the substrate is a disc-shaped holding member 11.

This carrier is used while being rotated by the sun gear and the internal gear in a state of being sandwiched between the upper and lower surface plates in the apparatus in the same manner as the processing object while being a non-processing object. Therefore, when the glass substrate is ground or polished, the holding hole of the carrier is always in contact with or away from the outer peripheral end surface of the glass substrate. At this time, the inner wall of the holding hole and the glass substrate rub against each other, so that scratches may occur on the end surface (particularly the side wall surface) of the glass substrate. If there is such a scratch, it becomes a dust generation source not only during the manufacture of the magnetic disk glass substrate but also during the subsequent manufacture of the magnetic disk or HDD. In addition, since the carrier material is insufficient for the carrier base material alone, the composite material such as glass fiber and epoxy resin is usually used to increase the strength. However, the glass fiber is used on the inner wall of the holding hole. If it protrudes or is exposed, it will be scratched or damaged when it comes into contact with the glass substrate end face.

Therefore, in Patent Document 1, for example, by etching a polishing carrier with hydrofluoric acid or the like, the glass fiber on the inner wall of the holding hole of the carrier is dissolved and removed to a certain depth, and a resin material having a plurality of recesses on the surface layer portion of the inner wall A technique for reducing damage to the end face of the glass substrate by providing a holding hole buffering region consisting of only the above is disclosed.
Further, Patent Document 2 provides damage to the glass substrate end face by providing a resin contact portion formed thicker than the fiber protruding from the inner wall surface on the inner wall surface of the holding hole of the polishing carrier. Techniques for reducing are disclosed.

JP 2012-218103 A JP 2008-000823 A

According to the study of the present inventors, when the glass substrate was polished using the polishing carrier disclosed in Patent Document 1, abrasive grains and glass sludge accumulated in the plurality of recesses arranged on the inner wall of the holding hole. It became clear that the coarse aggregates and the coarse aggregates came out of the recesses during polishing and caused scratches and surface contamination on the main surface of the glass substrate. In addition, the concave portion from which the glass fiber has been removed (the portion serving as the buffer region) can reduce the damage caused by the conventional glass fiber, but the strength is lowered by the removal of the glass fiber as the core material, and the glass substrate is processed during processing. When the contact is made, the periphery of the recess is destroyed, and the fragments become contamination, which causes scratches and surface contamination on the main surface of the glass substrate as described above. Furthermore, when the concave portion is broken, a step is generated on the inner wall of the holding hole, which may cause a new scratch on the end surface of the glass substrate, or the roundness of the inner diameter of the holding hole may be lost, and the roundness of the glass substrate may be reduced. There is a risk of breaking. Such various problems are particularly prominent during mass production, so that the durability when the carrier is used for a long time is poor.

Moreover, since the glass substrate for magnetic disks is normally processed into the thickness of 2 mm or less also including the thing in the middle of a process, the thing with an extremely thin board thickness of 2 mm or less is used also about the carrier holding this glass substrate.
In the case of the polishing carrier disclosed in Patent Document 2, a contact portion can be provided on the inner wall surface of the holding hole by, for example, resin coating, but the inner wall surface of the holding hole becomes a very narrow region because the plate thickness is thin. The adhesion of the abutting portion to the inner wall surface of the holding hole is low, and the abutting portion breaks or falls off due to contact with the glass substrate during processing, and the problem of damage due to exposure of the glass fiber is fundamental. It is difficult to solve.
The above-mentioned problem occurs not only in the glass substrate but also in the manufacture of an aluminum alloy substrate having a NiP film formed on the surface. When the main surface of the aluminum alloy substrate on which the NiP film is formed is polished using a double-side polishing apparatus while the substrate is held by a carrier. At this time, since the NiP film has a lower hardness than the glass substrate, the outer peripheral end face is easily scratched. Also, NiP sludge is generated by polishing.

Accordingly, the present invention has been made to solve such a conventional problem. The purpose of the present invention is, first, to reduce the occurrence of scratches during processing, and for a magnetic disk having good durability. It is to provide a carrier used for processing a substrate. A second object of the present invention is to provide a method for manufacturing a magnetic disk substrate and a method for manufacturing a magnetic disk, including processing for grinding or polishing the magnetic disk substrate using such a carrier.

As a result of earnest research, the present inventor has found that the above-described problems can be solved by the invention having the following configuration, and has completed the present invention.
That is, the present invention has the following configuration in order to achieve the above object.

(Configuration 1)
A carrier that is formed using a composite material including fibers and a resin material and has a holding hole for holding the substrate when the main surface of the disk-shaped substrate is polished or ground, and the holding hole The inner peripheral wall surface of the carrier has a plurality of recesses extending in the in-plane direction of the carrier and free of fibers, and the plurality of recesses are filled with a resin.

(Configuration 2)
The carrier according to Configuration 1, wherein the resin filled in the concave portion is a resin having a hardness lower than that of the resin material constituting the composite material.
(Configuration 3)
The carrier according to

Configuration

1 or 2, wherein the resin filled in the recess is a thermoplastic resin.

(Configuration 4)
4. The carrier according to claim 1, wherein Ra of the inner peripheral wall surface of the holding hole has a Ra of 1.0 μm or less.
(Configuration 5)
The carrier according to any one of configurations 1 to 4, wherein a distance in a carrier in-plane direction of a region including the plurality of concave portions filled with the resin is 100 μm or less.

(Configuration 6)
6. The carrier according to any one of configurations 1 to 5, wherein the resin filled in the recess covers an inner peripheral wall surface of the holding hole.
(Configuration 7)
Using the carrier according to any one of Structures 1 to 6, holding the disk-shaped substrate horizontally in the holding hole of the carrier, and pressing the processed surface of the surface plate against the main surface of the disk-shaped substrate A method of manufacturing a magnetic disk substrate comprising: processing a main surface of the disk-shaped substrate by relatively moving a processing surface of the surface plate and the disk-shaped substrate. .

(Configuration 8)
The processing is performed by supplying a polishing liquid containing abrasive grains between a polishing pad affixed to the surface of a surface plate and a main surface of the disk-shaped substrate, and the main surface of the disk-shaped substrate A method for manufacturing a magnetic disk substrate according to Configuration 7, wherein the magnetic disk substrate is polished.
(Configuration 9)
8. The method for manufacturing a magnetic disk substrate according to Configuration 7, wherein the processing is a grinding process in which a main surface of the disk-shaped substrate is ground with a surface plate to which fixed abrasive grains are attached.

(Configuration 10)
10. The magnetic disk substrate according to any one of Structures 7 to 9, wherein a difference between a hole diameter of the holding hole and an outer diameter of the disk-shaped substrate is 0.1 to 1.0 mm. Production method.
(Configuration 11)
11. The method for manufacturing a magnetic disk substrate according to any one of Structures 7 to 10, wherein the substrate is a glass substrate.

(Configuration 12)
A magnetic disk manufacturing method comprising: forming at least a magnetic recording layer on a magnetic disk substrate obtained by the manufacturing method according to any one of Structures 7 to 11.

The carrier according to the present invention has the above-described configuration, so that the agglomerates in which abrasive grains and glass sludge during processing are accumulated in the recesses from which the glass fibers existing on the inner walls of the holding holes of the carrier are removed, It is possible to provide a carrier used for processing a magnetic disk substrate having excellent durability, which can reduce the occurrence of debris due to the destruction of the surroundings, or scratches caused by glass fibers exposed on the inner wall of the holding hole. .
In addition, by grinding or polishing a magnetic disk substrate using such a carrier, it is possible to reduce scratches on the substrate main surface and end surface, which are obstructive factors in realizing high recording density of the medium. It is possible to manufacture a high-quality magnetic disk substrate that can be used. Furthermore, by using this substrate, it is possible to obtain a highly reliable magnetic disk that can obtain stable characteristics without failure.

It is a whole perspective view of the glass substrate for magnetic discs. It is a top view of the carrier concerning the present invention. It is a longitudinal cross-sectional view of the carrier of FIG. 2 which shows one Embodiment of the carrier based on this invention. It is a longitudinal cross-sectional view of the carrier of FIG. 2 which shows other embodiment of the carrier which concerns on this invention. 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. In the following embodiments, manufacturing of a glass substrate for a magnetic disk will be mainly described.
A glass substrate for a magnetic disk is usually manufactured through a rough grinding process, a shape processing process, a fine grinding process, an end surface polishing process, a main surface polishing process (first polishing process, second polishing process), a chemical strengthening process, and the like. The

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, rough grinding is performed on the main surface of the molded glass substrate to improve dimensional accuracy and shape accuracy. In this rough grinding process, a double-side grinding apparatus is usually used to grind the main surface of the glass substrate using loose abrasive grains or fixed abrasive grains. In addition, you may use the carrier of this invention. 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. This rough grinding step may be omitted as appropriate.

After the rough grinding step, a shape processing (chamfering) step is performed.
Thereafter, a precision grinding process is performed as appropriate. In this fine grinding step, for example, a grinding method using fixed abrasive grains using a diamond pad is suitable. A diamond pad is an agglomerate in which diamond particles or some diamond particles are hardened with a binder such as glass, ceramic, metal, resin, etc., and fixed using a support material such as resin (for example, acrylic resin). A pellet is pasted on a sheet. The diamond pad is not necessarily a general name, but is referred to as “diamond pad” here for convenience.
In grinding with fixed abrasive grains using a diamond pad, since the abrasive grains are uniformly present on the sheet surface, the load is not concentrated, and in addition, the abrasive grains are fixed to the sheet using resin, Even if a load is applied to the abrasive grains, the high elasticity of the resin that fixes the abrasive grains makes the cracks on the machined surface (work-affected layer) shallow, allowing the machined surface roughness to be reduced and reducing the load on subsequent processes ( The allowance is reduced. In addition, it is preferable to perform the grinding with the fixed abrasive while supplying a coolant such as water to the processing surface.

After that, after performing the end face polishing step, the main surface is mirror-polished to obtain a highly accurate plane. As a method for mirror polishing a glass substrate, it is preferable to use 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. .

It is preferable from the viewpoint of polishing efficiency that the colloidal silica abrasive grains contained in the above polishing liquid are those having an average particle diameter in the range of 1 to 50 nm. In particular, the abrasive grains contained in the polishing liquid used in the finishing mirror polishing process (second polishing process in the subsequent stage) should have an average particle diameter of 10 nm or more and less than 30 nm from the viewpoint of further reducing the surface roughness. It is preferred to use. More preferably, it is in the range of 10 to 20 nm.

In the present invention, the average particle size is a point where the cumulative curve is 50% when the cumulative curve is obtained with the total volume of the powder population in the particle size distribution measured by the light scattering method as 100%. (Hereinafter referred to as “cumulative average particle diameter (50% diameter)”). In the present invention, the cumulative average particle diameter (50% diameter) is specifically a value obtained by measurement using a particle diameter / particle size distribution measuring apparatus.

As a polishing method, the glass substrate and the polishing pad are brought into contact with each other, and the polishing pad and the glass substrate are moved relative to each other while supplying a polishing liquid containing polishing abrasive grains, thereby polishing the surface of the glass substrate in a mirror shape. do it.

FIG. 5 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, and the configuration thereof is as already described. The double-side polishing apparatus shown in FIG. 5 meshes with the sun gear 2, the internal gear 3 arranged concentrically on the outside thereof, 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 each having a carrier 10 that revolves and rotates in accordance with the rotation of the substrate 10 and a polishing pad 7 that can hold the workpiece 1 held by the carrier 10. A polishing liquid supply unit (not shown) for supplying a polishing liquid is provided between the panel 5 and the lower surface plate 6.

lower surface plates

5 and 6 are polished. While supplying the polishing liquid between the pad 7 and the workpiece 1, the carrier 10 revolves and rotates according to the rotation of the sun gear 2 and the internal gear 3, and the upper and lower surfaces of the workpiece 1 are moved. Polished.

The present invention relates to the carrier 10 used for holding a glass substrate which is an object to be processed in the above polishing process.
The carrier according to the present invention, for example, presses the processing surface of the surface plate against the main surface of the glass substrate, relatively moves the processing surface of the surface plate and the glass substrate, and moves the main surface of the glass substrate. It is a carrier that is used when processing and holds the glass substrate horizontally. And as it exists in the said structure 1, it forms using the composite material containing a fiber and a resin material, and hold | maintains the said glass substrate when grind | polishing or grinding the main surface of a disk-shaped glass substrate A carrier having a holding hole, wherein the inner peripheral wall surface of the holding hole is in a direction substantially perpendicular to the inner peripheral wall surface, for example, and extends in the in-plane direction of the carrier, and a plurality of fibers that do not exist It has a recessed part and the said several recessed part is set as the structure filled with resin.

2 and 3 each show an embodiment of a carrier according to the present invention. FIG. 2 is a plan view of the carrier according to the present invention. FIG. 3 is a longitudinal sectional view of the carrier of FIG. 2 showing an embodiment of the carrier according to the present invention.

As shown in FIG. 2, a carrier 10 according to an embodiment of the present invention is composed of a disk-shaped holding member 11 as a whole and includes a plurality of holding holes 12 for holding a glass substrate. The plurality of holding holes 12 are all circular in order to uniformly grind and polish the main surface of the glass substrate, and to suppress generation of scratches due to local contact with the end surface of the glass substrate. Desirably, it is formed in a perfect circle as in this embodiment. From the above viewpoint, the roundness of the holding hole is preferably, for example, 20 μm or less. The roundness of the holding hole can be measured by, for example, a roundness / cylindrical shape measuring machine. The holding hole 12 can be formed, for example, by drilling a hole of a predetermined size in the base material of the disk-shaped holding member 11.

The difference between the hole diameter (diameter) of the holding hole 12 and the outer diameter of the glass substrate held in the holding hole 12 is usually 0.1 to 1.0 mm regardless of the size of the glass substrate. It is preferable. If it is larger than 1.0 mm, the followability to the carrier motion (planetary gear motion) of the glass substrate is deteriorated, and grinding or polishing unevenness may occur on the main surface. On the other hand, if the thickness is less than 0.1 mm, the degree of freedom of movement of the glass substrate in the holding hole becomes too low, and the force concentrates on the same portion of the end portion, which may easily cause scratches. Moreover, it becomes difficult to attach and detach the substrate from the carrier.

A plurality of gear teeth 13 that mesh with the sun gear 2 and the internal gear 3 of the double-side polishing apparatus are formed on the outer peripheral portion of the holding member 11.

As shown in the longitudinal sectional view of FIG. 3, the holding member 11 is formed of a composite material including glass fibers 30 and a resin material A (for example, epoxy resin) 31 except for a region A1 described later. Yes. Specifically, for example, it is formed of a base material in which glass fibers are laminated in an epoxy resin (or a laminate of a plurality of such base materials).
In addition, for example, metal fibers can be used instead of glass fibers. In this case, the case where a holding member is formed with the composite material containing glass fiber and a resin material is illustrated as an example.
In FIG. 3, for convenience of illustration, the internal cross-sectional structure of the holding member 11 (particularly, the region made of the composite material) is merely depicted as an image, and the actual internal structure is not necessarily accurately depicted. .

Further, as shown in FIG. 3, the inner peripheral wall surface of the holding hole 12 includes a plurality of glass fibers extending in the in-plane direction of the carrier that are orthogonal to the inner peripheral wall surface and do not exist. The plurality of recesses 20 are filled with a resin material B21 that is the same as or different from the resin material A31. Then, the resin material A31 including the plurality of recesses 20 and the resin material B21 are formed in the in-plane direction of the carrier main surface from the inner peripheral wall surface of the holding hole 12 toward the outside of the holding hole. A region A1 is provided. In other words, the predetermined area A1 extending outward from the inner peripheral wall surface of the holding hole 12 is formed by the resin material A31 and a plurality of recesses 20 filled with the same or different resin material B21 as the resin material A31. And the area | region except the said area | region A1, ie, area | region A2 of the carrier outer periphery side of said area | region A1, is formed with the composite material containing the glass fiber 30 and the resin material A31 as above-mentioned. In the present invention, in the region A1, glass fibers stretched in a direction parallel to the inner peripheral wall surface of the holding hole 12 may exist.

The concave portion 20 included in the region A1 is exposed on the inner peripheral wall surface of the holding hole 12 formed by drilling a hole of a predetermined size in the base material of the holding member 11 made of the composite material, for example. The glass fiber can be formed by dissolving and removing it to a certain depth (corresponding to the region A1). Examples of the method for dissolving and removing the glass fiber in this case include a method of etching the carrier in which the holding hole 12 is formed with hydrofluoric acid or the like. Then, the resin material B21 is filled in the recess formed by melting and removing the glass fiber to a certain depth in this way, so that the resin material A31 and the resin material B21 that is the same as or different from the resin material A31 are filled. A region A1 composed of the plurality of recessed portions 20 is formed.

As described above, the resin material A31 contained in the glass fiber and resin composite material basically constituting the carrier 10 of the present invention is generally an epoxy resin, but in addition to this, for example, a phenol resin, Bismaleimide resin, silicone resin, diallyl phthalate resin, unsaturated polyester resin, polyphenylene sulfide resin, etc. may be used.

The resin material B21 filled in the recess 20 included in the region A1 of the carrier 10 of the present invention is, for example, an epoxy resin as long as it is the same resin material as the resin material A31. Further, any resin material different from the above resin material A31 can be used without any particular restriction, but from the viewpoint of the filling method described later, a thermoplastic resin is particularly preferable. For example, polycarbonate, polyoxymethylene, polypropylene At least selected from resins such as polyphenylene sulfide, polyamide, polyethylene, polystyrene, acrylic, polyethylene terephthalate, polyphenylene ether, polyacetal, polybutylene terephthalate, polyphephenylene sulfide, polyether ether ketone, fluororesin, urethane resin, liquid crystal polymer, and elastomer. One type is preferable.

A thermosetting epoxy resin is generally used for the resin material of the carrier substrate for the convenience of the manufacturing process. Therefore, when the concave portion 20 is filled with the same thermosetting epoxy resin, strong friction is generated between the wall surface of the holding hole and the edge of the glass substrate during processing, and even when frictional heat is locally generated, Since it does not deform | transform especially, it is easy to generate | occur | produce an end surface crack on a glass substrate. On the other hand, when the concave portion 20 is filled with, for example, a thermoplastic resin different from the resin material of the carrier base material, the glass substrate is not easily damaged because of a slight deformation due to frictional heat. Further, when a resin having a lower hardness than the epoxy resin of the carrier substrate is used, it plays a role of a cushion, so that the end face scratch is hardly generated on the glass substrate.

Therefore, it is preferable that the resin filled in the recess 20 is a thermoplastic resin.
Moreover, it is preferable that resin with which the said recessed part 20 is filled is resin whose hardness is lower than the resin material which comprises the composite material which is a carrier base material. In this case, it is preferable that the resin to be filled has a Rockwell hardness of less than M80. By setting it within this range, it is possible to make the hardness lower than that of the epoxy resin of the base material, so that it is possible to make it difficult to cause scratches on the end face of the glass substrate. The hardness of the epoxy resin is generally M80 to 100 in terms of Rockwell hardness.

Examples of the method for filling the recess 20 with the resin material B21 include the following methods.
After the resin material B21 is applied to the inner peripheral wall surface of the holding hole 12, heating is performed to melt and fill the resin material B21. At this time, if the inside of the recessed portion of the filling portion can be depressurized, it is more preferable because the bottom of the recessed portion can be filled. For example, the coating may be performed in a reduced pressure environment and then heated to normal pressure. As a heating method, it is preferable to apply a hot plate welding method, a vibration welding method, an ultrasonic welding method, a laser transmission welding method, or the like. The above filling operation can be efficiently performed in a state where a large number of carrier holding members 11 are stacked. In addition, you may remove the resin which protruded from the recessed part after the filling process. For example, a rotary blade can be used to remove the resin.

The resin material B21 may not be completely filled up to the bottom of the recess. As long as the entrance of the recess is blocked, it is possible to prevent abrasive grains and sludge from entering the recess. In addition, it is preferable that the depth at which the resin material B21 is filled from the entrance of the recess is 1 μm or more because the resin material B21 is less likely to drop off and durability due to the thickness is increased. The depth is more preferably 2 μm or more, and further preferably 5 μm or more. Note that it is most preferable that the resin material B21 is completely filled in the concave portion because the adhesiveness with the carrier is maximized.

In the carrier 10 of the present invention, the distance between the resin material A31 and a region A1 (including) a plurality of recesses 20 filled with the same or different resin material B21 as the resin material A31 is 100 μm or less. Is preferred. When it exceeds 100 μm, the strength of the region near the inner wall of the holding hole is lowered, and the roundness of the holding hole may be deteriorated. On the other hand, if it is less than 1 μm, the effects of the present invention may not be sufficiently obtained.

In the carrier 10 of the present invention, the surface roughness of the inner peripheral wall surface of the holding hole is preferably an arithmetic average roughness Ra of 1.0 μm or less. If it is this range, the flaw generation | occurrence | production of the end surface of the glass substrate in process can be suppressed.

As described above, the carrier 10 of the present invention according to the present embodiment has a plurality of recesses 20 filled on the inner peripheral wall surface of the holding hole 12 with the resin material B21 that is the same as or different from the resin material A31. Since the region A1 including the recess 20 filled with resin is provided in the direction from the inner peripheral wall surface to the outside of the holding hole, the region A1 in the vicinity of the inner peripheral wall surface of the holding hole 12 is made of only the resin material. Since glass fibers formed and at least stretched in a direction perpendicular to the inner peripheral wall surface are not included, the glass substrate end face can be protected by elastic deformation of the resin material in the region A1, and a glass substrate due to conventional glass fiber protrusion or exposure There will be no scratches on the end face.

Further, since the plurality of recesses 20 in the inner wall of the holding hole 12 are filled with the resin material B21, abrasive grains and glass sludge do not stay in the recesses 20, and the abrasive grains and glass sludge collected in the recesses of the prior art. Can solve the problem of coarsening and coming out of the recess and causing scratches and surface contamination on the main surface of the glass substrate. Further, since the recess 20 is filled with the resin material B21, the strength reduction around the recess is suppressed, the periphery of the recess of the prior art is destroyed, and the fragments become contamination, and the glass substrate main surface is scratched. Problems that cause surface contamination can be solved.

Furthermore, when the conventional recess is broken, a step is generated on the inner wall of the holding hole, which may cause a new scratch on the end surface of the glass substrate, or the roundness of the inner diameter of the holding hole may be lost. The problem of breaking down to the extent can also be solved.
Since the carrier 10 of the present invention can solve various problems of the prior art that are particularly prominent during mass production, it is excellent in durability when the carrier is used for a long period of time.

FIG. 4 is a longitudinal sectional view of the carrier of FIG. 2 showing another embodiment of the carrier according to the present invention.
As shown in FIG. 4, in the present embodiment, the surface of the inner peripheral wall surface of the holding hole 12 is covered with the resin material B21 filled in the recess 20, and the recess 20 filled with the resin material B21. And the surface portion of the inner peripheral wall surface covered with the resin material B21 is continuous.

In the present embodiment, the thickness t in the carrier plane direction of the resin material B21 covering the inner peripheral wall surface of the holding hole 12 is not particularly limited, but is preferably in the range of about 1 μm to 2 mm. The thickness and surface properties can be adjusted by forming the film thickly and then cutting it with a rotary blade.

Further, according to the carrier according to the present embodiment, in addition to the effects obtained by the carrier of the embodiment as shown in FIG. 3 described above, the entire inner peripheral wall surface of the holding hole 12 is made of resin material. By being covered with B21, the effect that the surface roughness of the inner peripheral wall surface of the holding hole 12 can be further improved can be obtained. Specifically, Ra can be 0.5 μm or less.

Although the inner wall surface of the holding hole is a very narrow region because the thickness of the carrier is thin, the surface portion of the inner peripheral wall surface of the holding hole covered with the resin material B21 is continuous with the concave portion 20 filled with the resin material B21. Therefore, it is possible to prevent the surface portion covering the inner peripheral wall surface of the holding hole from being damaged or dropped due to contact with the glass substrate during processing.

Conventionally, in a carrier having a thin plate thickness of 2 mm or less, such as for a magnetic disk glass substrate, for example, when the inner peripheral wall surface of a holding hole as disclosed in Patent Document 2 is covered with a resin material, for example, a coating method However, in this method, the thickness could be increased only to about 50 microns in the in-plane direction. This is because the thickness of the carrier is small and the adhesive surface is small, and when the thickness is increased, the carrier is peeled off from the inner peripheral wall surface. There is also a method of fitting a ring-shaped member different from the carrier inside the holding hole, but it is not fixed, or even if it is temporarily fixed, the adhesive force is weak, and it will be detached from the holding hole during processing However, it was unsuitable for mass production.
However, in the present embodiment, since the root (convex portion formed in the concave portion) is formed on the inner peripheral wall surface of the holding hole, the adhesive force can be strengthened more than the conventional method. The thickness t can be greatly increased. For example, the thickness t can be 100 μm or more, or 0.5 mm or more. Since the thickness can be increased in this way, the effect of preventing end face scratches can be stably obtained over a long period of time.

In addition, in the mirror polishing process of the glass substrate using the carrier of the present invention as described above, the applied load (working surface pressure) is preferably in the range of 10 gf / cm ² or more and 300 gf / cm ² or less. The lower limit value is more preferably 50 gf / cm ² or more. Further, the upper limit is more preferably 200 gf / cm ² or less.
When the load is lower than 10 gf / cm ² , the workability (polishing rate) of the glass substrate may be lowered, which is not preferable. Moreover, when higher than 250 gf / cm < ² >, since scratches, such as a scratch, may generate | occur | produce on the glass substrate surface, it is unpreferable.

In general, the mirror polishing process is performed in the first polishing process for removing scratches and distortions remaining in the lapping process, and the surface roughness of the main surface of the glass substrate while maintaining the flat surface obtained in the first polishing process. In general, it is performed through two stages of a second polishing process that finishes the surface to a smooth mirror surface (however, multistage polishing of three or more stages may be performed). The first polishing and the second polishing Since it is preferable to carry out using the same polishing apparatus, it is preferable to apply the carrier of the present invention in both the first polishing and the second polishing.

In addition, although the case where the carrier according to the present invention is applied in the polishing treatment of the glass substrate has been described above, the double-side grinding apparatus having the same configuration as the above-described double-side polishing apparatus is also used in the grinding process of the glass substrate main surface. Therefore, it is preferable to apply the carrier according to the present invention described above also in the grinding processing of the glass substrate performed using this double-side grinding apparatus.
The carrier of the present invention is particularly suitable for grinding using fixed abrasive grains (for example, precision grinding using the aforementioned diamond pad). In precision grinding using fixed abrasive grains, only a large amount of glass sludge is generated, so that the purity of the glass sludge tends to be high. This is because a problem occurs remarkably.

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 the present invention, the surface of the glass substrate after the mirror polishing treatment has an arithmetic average surface roughness Ra of 0.20 nm or less when the AFM is used to measure a range of 1 μm × 1 μm with a resolution of 256 × 256 pixels. A certain mirror surface is preferable. In the present invention, Ra is a roughness calculated in accordance with Japanese Industrial Standard (JIS) B0601.

According to the present invention, it is possible to produce a high-quality glass substrate that can reduce scratches on the main surface and end face of the glass substrate, which is an impediment to achieving high recording density of the medium, 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 having a DFH type magnetic head capable of realizing an ultra-low flying height.
In the above embodiment, the case where the present invention is mainly applied to the manufacture of a glass substrate for a magnetic disk has been described. However, the present invention forms not only such a glass substrate but also a NiP film on the surface. The present invention can be applied in the same manner to the manufactured aluminum alloy substrate, and the same effect of the present invention can be obtained.

The present invention also provides a method of manufacturing a magnetic disk using, for example, a glass substrate for the above magnetic disk.
The magnetic disk is manufactured by forming at least a magnetic recording layer (magnetic layer) on the glass substrate for a magnetic disk according to the present invention. Further, a protective layer and a lubricating layer may be formed in this order on the magnetic recording layer.

By using the glass substrate obtained by the present invention, a highly reliable magnetic disk that can obtain stable characteristics without causing a head crash or the like even when recording / reproducing with a DFH head, for example, can be obtained. . Therefore, it is suitable for manufacturing a magnetic disk having a higher recording density than ever before, for example, exceeding 500 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.
(Example 1, 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 (first polishing step), (6) chemical strengthening step (7) A glass substrate for a magnetic disk was manufactured through a main surface polishing step (second 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.
This glass substrate was subjected to a rough grinding process 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 performed the grinding process by said fixed abrasive using 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 (first polishing step)
Next, the 1st grinding | polishing process of the main surface was performed using the double-side polish apparatus. 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.

The carrier according to the embodiment of the present invention shown in FIG. 2 and FIG. 3 was applied as the carrier. This carrier uses a composite material containing glass fiber and epoxy resin as a carrier base material, and the glass fiber on the inner wall of the holding hole is dissolved and removed to a depth of 10 μm by etching with hydrofluoric acid, and the formed recess is filled with polycarbonate resin. Is. Specifically, a polycarbonate resin was applied under reduced pressure conditions, returned to normal pressure, and then heated to completely fill the recess, and the polycarbonate resin protruding from the recess after the treatment was removed with a rotary blade. The polycarbonate resin has a Rockwell hardness of M78. The diameter of the holding hole was set to 65.5 mm so as to be suitable for processing a 2.5-inch glass substrate. The roundness of the holding hole was 15 μm. The thickness of the carrier is 0.5 mm.

Thereafter, the polishing liquid was supplied between the polishing pad and the polishing surface of the glass substrate and rotated, whereby the glass substrate revolved while rotating on the surface plate, and both surfaces were polished simultaneously. A hard polisher (hard urethane foam) was used as the polishing pad, and the polishing liquid was a dispersion of cerium oxide having an average particle size of 1.5 μm as an abrasive. The glass substrate after the first polishing step was washed and dried.
In the first polishing step, when a plurality of carriers are used in one polishing, the same type is used, and 100 batches are processed without replacing the carriers. The number of processed sheets per batch is 50 sheets.

(6) Chemical strengthening process Next, the glass substrate which finished the said washing | cleaning was chemically strengthened.

(7) Main surface polishing step (second polishing step)
Next, using the same double-side polishing apparatus as used in the first polishing step, the polishing pad was replaced with a polishing pad (foamed polyurethane) of a soft polisher (suede), and a second polishing step was performed. The carrier used in the second polishing step was the same type as the carrier used in the first polishing step. This second polishing step is a mirror polishing process for finishing the surface roughness of the glass substrate main surface to a smooth mirror surface with an Ra of about 0.2 nm or less. As the polishing liquid, a dispersion of colloidal silica polishing abrasive grains having an average particle diameter of 20 nm in water was used. The glass substrate after the second polishing step was washed and dried.

The glass substrate for magnetic disk was produced through the above steps. The obtained glass substrate has a circular hole 103 in the center as shown in FIG. 1, and is a disk provided with both

main surfaces

101, 102 and an inner peripheral end surface 104 and an outer peripheral end surface 105 between the two main surfaces. A glass substrate 100 having an outer diameter of 65 mm, an inner diameter of 20 mm, a plate thickness of 0.635 mm, and a roundness of 1.5 μm.

About the glass substrate of the 100th batch of the first polishing step, the outer peripheral end face of the glass substrate was visually observed while applying a condenser lamp in a dark room, and the presence or absence of scratches due to contact with the carrier was confirmed. I couldn't see it. Further, when the main surface was measured with an optical surface analyzer, no particular scratch was found.

Further, as Comparative Example 1 with respect to Example 1 described above, in the first polishing step and the second polishing step, a composite material containing glass fibers and an epoxy resin is used as a carrier substrate, and the inner wall of the holding hole is etched by hydrofluoric acid. For a magnetic disk in the same manner as in Example 1 except that a carrier in which glass fibers are dissolved and removed to a predetermined depth (10 μm) (that is, nothing is filled in the recesses formed on the inner wall) is applied. A glass substrate was produced.
About the glass substrate of the 100th batch of the 1st grinding | polishing process, when the outer periphery end surface and main surface of the glass substrate were observed similarly to the said Example 1, the damage | wound by contact with a carrier is per 1 board | substrate on an outer periphery end surface. An average of 6 scratches was found, and an average of 5 scratches or pit defects was observed per substrate surface on the main surface.

(Example 2, comparative example 2)
Furthermore, in the fine grinding step of (3) above, similarly to the above, grinding is performed 100 batches using the same carrier as in Example 1 and Comparative Example 1, and the glass substrate of the 100th batch is washed and dried, The main surface and the outer peripheral end face were observed (Example 2 and Comparative Example 2). The main surface was observed by visual inspection. As a result, when the same carrier as in Comparative Example 1 was used in the fine grinding step, an average of 13 scratches at the outer peripheral edge and an average of 3 long scratches on the main surface were found. On the other hand, when the same carrier as in Example 1 was used, both were 0.

As can be seen from the above results, in the case of applying the carrier of the embodiment of the present invention and performing a mirror polishing process on the surface of the glass substrate with a double-side polishing apparatus, or when performing a grinding process, the glass substrate in the 100th batch However, surface defects such as scratches were not observed, and good results were obtained. Moreover, when the carrier after 100 batches of glass substrate preparation was observed in detail, the damage of the inner wall of a holding hole, etc. were not seen.

On the other hand, in the case where the carrier of the comparative example is applied and the surface of the glass substrate is mirror-polished by a double-side polishing apparatus or when the grinding treatment is performed, the glass substrate of the 100th batch has surface defects such as scratches. It was observed on both the main surface and the outer peripheral end face. Moreover, when the carrier after 100 batches of glass substrate preparation was observed in detail, the damage of the inner wall of a holding hole was seen.

Thus, when the carrier of a comparative example is applied, the following points are mentioned as a cause which surface defects, such as a crack | wound, generate | occur | produced in the glass substrate.
1. Agglomerates, which were coarsened due to accumulation of abrasive grains and glass sludge in the recesses in the inner wall of the holding hole, came out of the recesses during polishing and caused scratches and surface contamination on the end surfaces and the main surface of the glass substrate.
2. There is no glass fiber on the inner wall of the holding hole, it has a plurality of recesses that are not filled with anything, and the strength of the inner wall of the holding hole is low, so it breaks due to contact with the glass substrate during processing As a result, the fragments were contaminated, and scratches and surface contamination were caused on the glass substrate end face and the main surface as in 1 above.

Example 3
In this example, the carrier according to the embodiment shown in FIG. 4 was applied. This carrier uses a composite material containing glass fiber and epoxy resin as a carrier base material, and the glass fiber on the inner wall of the holding hole is dissolved and removed to a depth of 10 μm by etching with hydrofluoric acid, and the formed recess is filled with polycarbonate resin. Thereafter, the removal amount was adjusted with a cutting blade so that the thickness t in the carrier plane direction from the inner wall of the holding hole was 1 mm. In this state, the diameter of the holding hole was set to 65.5 mm.
As in Example 1, 200 batches of glass substrates were processed using the carrier for the first and second polishing. When the glass substrate of the 200th batch was observed on the outer peripheral end face and the main surface of the glass substrate in the same manner as in Example 1, no scratches or scratches were found on the outer peripheral end face and the main surface.

(Comparative Example 3)
Polycarbonate so that the inner wall of the holding hole of a conventional carrier (a composite material containing glass fiber and epoxy resin is used as a carrier base material and the glass fiber of the inner wall of the holding hole is not dissolved and removed by hydrofluoric acid etching) has a thickness of 1 mm. Resin coating was applied. In this state, the diameter of the holding hole was set to 65.5 mm. As in Example 3, 200 batches of glass substrates were processed using this carrier for the first and second polishing. As for the 200th batch of glass substrates, the outer peripheral end face and the main surface were observed. On the outer peripheral end face, an average of 25 scratches per substrate were found, and the main surface averaged 11 per substrate face. Scratch or pit defects were observed.

(Comparative Example 4)
A ring-shaped polycarbonate resin member having a thickness of 1 mm was fitted to the inner wall of the holding hole of the conventional carrier (without etching treatment). In this state, the diameter of the holding hole was set to 65.5 mm. When the glass substrate was processed using this carrier for the first and second polishing, the ring-shaped member was detached during the polishing for both the first and second polishing, and 200 batch processing could not be performed.

From the above results, when the carrier of the embodiment shown in FIG. 4 is used, stable production is possible without causing scratches or the like on the outer peripheral end face or main surface of the glass substrate over a long period of time.

(Manufacture of magnetic disk)
The following film formation process was performed on the magnetic disk glass substrate obtained in Example 1 to obtain a magnetic disk 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.

The obtained magnetic disk was incorporated into an HDD together with a DFH head and subjected to a long-term operation test. As a result, no problems such as a head crash occurred and a good result was obtained.

1 Workpiece to be polished (glass substrate)
2 Sun gear 3 Internal gear 5 Upper surface plate 6 Lower surface plate 7 Polishing pad 10 Carrier 11 Holding member 12 Holding hole 13 Gear tooth 20 Recess 21 Resin material B
30 Glass fiber 31 Resin material A
DESCRIPTION OF SYMBOLS 100 Glass substrate 101,102 for magnetic discs Main surface 103 Circular hole 104 Inner peripheral end surface 105 Outer peripheral end surface

Claims

A carrier having a holding hole for holding the substrate when polishing or grinding the main surface of the disk-shaped substrate, formed using a composite material including fibers and a resin material,
The inner peripheral wall surface of the holding hole has a plurality of recesses extending in the in-plane direction of the carrier and free of fibers,
The carrier, wherein the plurality of recesses are filled with resin.
2. The carrier according to claim 1, wherein the resin filled in the recess is a resin having a lower hardness than a resin material constituting the composite material.
3. The carrier according to claim 1 or 2, wherein the resin filled in the recess is a thermoplastic resin.
The carrier according to any one of claims 1 to 3, wherein Ra of the inner peripheral wall surface of the holding hole has a surface roughness Ra of 1.0 µm or less.
The carrier according to any one of claims 1 to 4, wherein a distance in a carrier in-plane direction of a region including a plurality of concave portions filled with the resin is 100 µm or less.
The carrier according to any one of claims 1 to 5, wherein the resin filled in the recess covers an inner peripheral wall surface of the holding hole.
A carrier according to any one of claims 1 to 6, wherein a disk-shaped substrate is horizontally held in a holding hole of the carrier, and a processing surface of a surface plate is pressed against a main surface of the disk-shaped substrate. And manufacturing the magnetic disk substrate, wherein the processing surface of the surface plate and the disk-shaped substrate are relatively moved to process the main surface of the disk-shaped substrate. Method.
The processing is performed by supplying a polishing liquid containing abrasive grains between a polishing pad affixed to the surface of a surface plate and a main surface of the disk-shaped substrate, and the main surface of the disk-shaped substrate The method for manufacturing a magnetic disk substrate according to claim 7, wherein the magnetic disk substrate is a polishing process for polishing the substrate.
The method for manufacturing a magnetic disk substrate according to claim 7, wherein the processing is a grinding process in which a main surface of the disk-shaped substrate is ground with a surface plate to which fixed abrasive grains are attached.
10. The magnetic disk substrate according to claim 7, wherein a difference between a diameter of the holding hole and an outer diameter of the disk-shaped substrate is 0.1 to 1.0 mm. Manufacturing method.
11. The method for manufacturing a magnetic disk substrate according to claim 7, wherein the substrate is a glass substrate.
A method for manufacturing a magnetic disk, comprising forming at least a magnetic recording layer on a magnetic disk substrate obtained by the manufacturing method according to claim 7.