JP5074311B2 - Magnetic disk glass substrate processing method, magnetic disk glass substrate manufacturing method, and magnetic disk manufacturing method - Google Patents

Description

  The present invention relates to a magnetic disk mounted on a magnetic recording device such as a hard disk drive (HDD), and more specifically, a method for processing a glass substrate for a magnetic disk by processing an end surface of a glass substrate for a magnetic disk by grinding, and a glass by this processing method. The present invention relates to a glass substrate for a magnetic disk having a grinding process of a substrate end face and a method for manufacturing the magnetic disk.

Today, information recording technology, particularly magnetic recording technology, is required to undergo dramatic technological innovation with the rapid development of IT industry. In a magnetic disk that is a recording medium mounted on an information recording apparatus such as a hard disk drive (HDD), a technology capable of realizing an information recording density of 40 Gbit / inch ^{2 to} 100 Gbit / inch ² or more is demanded in response to a request for high capacity. Yes.

  By the way, as an information recording medium substrate such as a magnetic disk, conventionally, an aluminum-based alloy substrate has been widely used. Recently, however, a ratio of a glass substrate as a magnetic disk substrate suitable for high recording density has been increased. It is getting higher gradually. Since the glass substrate has higher rigidity than the aluminum-based alloy substrate, it is suitable for high-speed rotation of the magnetic disk device, and a smooth surface can be obtained, so that it is easy to reduce the flying height of the magnetic head, and recording This is preferable because the S / N ratio of the signal can be improved.

In addition, in order to increase the recording density of the magnetic disk, high processing accuracy is required for the glass substrate, which is the same not only for the main surface of the glass substrate but also for the end face shape.
A glass substrate for a magnetic disk is usually produced by sequentially performing steps such as grinding, polishing, and chemical strengthening on a glass substrate formed into a disk shape.

  As a conventional method for grinding the end surface of a glass substrate, grinding is performed by rotating a grinding wheel in contact with the outer peripheral side end surface and the inner peripheral side end surface of the glass substrate while supplying a grinding liquid to the end surface portion of the glass substrate formed into a disk shape. Processing was performed, and predetermined chamfering was performed on the outer peripheral side end surface and the inner peripheral side end surface of the glass substrate (Patent Document 1, etc.).

JP 2000-185927 A

With the progress of the information society, demands for higher recording density and lower prices of magnetic disks are increasing day by day. Also in the end face shape of a magnetic disk, further smoothing, improvement in processing accuracy, reduction in processing time, and improvement in the life of auxiliary materials have been demanded.
In addition, the hard disk drive described above is not only mounted on a conventional personal computer or the like, but in recent years, the capacity has been increased as a recording medium for home video recorders and video cameras. Therefore, since it is necessary to dramatically increase the recording density of the magnetic disk, an inexpensive and high-performance magnetic recording medium has been used.

There is a need for such a low-cost magnetic recording medium that can achieve high recording density. To that end, for example, the accuracy of the inner diameter dimension to obtain the positioning accuracy of the read / write head, the occurrence of corrosion on the main surface of the medium, etc. It is required to achieve high quality of the outer diameter end face based on the request to reduce the contamination factor.
However, in the current end face processing process, the damage to the substrate that occurs during grinding (using electrodeposition wheels # 325, # 500, etc.) is large and the cracks are deep, so the polishing allowance in the next polishing process is easy. Therefore, there is a problem that the process has a problem that dimensional accuracy is difficult to stabilize and residual cracks are likely to remain on the end face.

  Therefore, the demand for further improvement in ensuring reliability as a magnetic recording medium has increased the demand for realizing grinding with low damage on the inner and outer diameter end faces of the substrate. Therefore, there is a need for a grinding process that can reduce damage compared to the conventional end face grinding process. Furthermore, the ability to achieve mirror grinding by this improvement leads to the achievement of both post-polishing quality, size and shape accuracy.

  And, from the viewpoint of further increasing the information recording density, the quality requirements for the glass substrate for magnetic disks, such as the dimensional accuracy of the end face of the glass substrate and the finished surface quality of the chamfering process, are increasing more than before, When many glass substrates for magnetic disks are manufactured using conventional grinding and polishing methods, there is a problem that it is becoming increasingly difficult to stably meet the increasing quality requirements of glass substrates. Although possible substrates can be reworked, there is a problem that costs increase.

  Therefore, the present invention is particularly suited for the end face on the outer peripheral side of a glass substrate for a magnetic disk from the viewpoint of meeting the demand for higher recording density and lower price of a magnetic disk, which is urgently required to ensure reliability for higher recording density. The first object of the present invention is to provide a method for processing a glass substrate for a magnetic disk, which enables a stable grinding process that can be efficiently finished with high quality at a low cost. A second object of the present invention is to provide a method for manufacturing a glass substrate for a magnetic disk and a method for manufacturing a magnetic disk, each of which includes a grinding process step of the glass substrate end face by such a processing method.

  As described above, when chamfering of the end surfaces of a large number of glass substrates for magnetic disks is performed using a conventional grinding method, the side wall surface orthogonal to the main surface of the glass substrate, for example, the outer peripheral side end surface of the glass substrate In addition, it is possible to stably meet the increasing quality requirements of glass substrates such as the dimensional accuracy of the two chamfered surfaces formed between the side wall surface and the main surface of the front and back surfaces and the finished surface quality of the chamfering process. It has become increasingly difficult.

  Conventional chamfering of the end face of a glass substrate for magnetic disks is performed by a grinding manner similar to intermittent creep grinding in order to process predetermined dimensions with high efficiency. Therefore, conventionally, by using a grindstone having a coarse particle size (large particle size), a large cutting amount (grindability) for ensuring a necessary removal speed is obtained. However, such a large depth of cut becomes a grinding process in a brittle fracture mode, and it is difficult to obtain a good ground surface quality (mirror surface quality) by a grinding process mainly based on a plastic mode. Conventionally, the end surface is ground and then the end surface is subjected to a mirror polishing process to obtain mirror surface quality. However, if the depth of cut is large, the grinding surface processing distortion becomes deeper and mirror polishing is performed. However, distortion and streaks may remain and high quality may not be obtained. Therefore, in order to obtain a good quality of the ground surface, it is necessary to perform grinding processing mainly of the plastic mode on a regular basis. For this purpose, for example, a grindstone having a fine grain size (small or fine grain size) is used. It is possible. According to the inventor's study, in the case of a glass material, the thermal conductivity and thermal diffusivity are low compared to metal materials and other inorganic materials (Si, Ge, etc.), and the local temperature change due to grinding is severe. For this reason, when the yield point of the glass material is lowered, the grindability and brittle fracture are likely to occur. And, when using a fine abrasive wheel, its grindability is low, the current cutting amount giving priority to processing efficiency cannot follow the removal efficiency required for abrasive grains, it becomes a grinding state such as crushing and clogging, Burning occurs in the grindstone, and grinding becomes impossible in a short time. That is, according to the inventor's study, with a glass material such as a magnetic disk substrate, a fine abrasive grindstone has a large change in the properties of the grindstone, and it is difficult to ensure stable grindability. It has been found that it is difficult to obtain a stable mirror quality of the end face.

  In addition, the end face of the glass substrate for magnetic disks is a chamfered shape with a chamfer surface, and the tolerance accuracy requirements including the inner and outer diameter tolerances are also included in each shape. In order to ensure the dimensional shape accuracy by processing, it is necessary to maintain the sharpness while suppressing the wear of the grindstone (while maintaining the shape maintenance) and to stably ensure the grindability for realizing the plastic mode.

Therefore, the present inventor has intensively studied to solve the above problems based on such a series of findings, and has completed the present invention.
That is, the present invention has the following configuration in order to solve the above problems.

(Configuration 1) Glass for a magnetic disk that processes the end surface of the glass substrate by supplying a grinding liquid to the end surface portion of the disk-shaped glass substrate and grinding by bringing a grindstone into contact with the end surface on the outer peripheral side of the glass substrate. A method for processing a substrate, wherein the grindstone is formed in a cylindrical shape and has a groove shape on an inner peripheral side thereof, the groove shape including a side wall surface of an outer peripheral side end surface of the glass substrate, and the glass It is formed so that both the chamfered surface between the main surface and the side wall surface of the substrate can be ground simultaneously, the outer peripheral side end surface of the glass substrate is brought into contact with the inner peripheral side of the grindstone, and the A method of processing a glass substrate for a magnetic disk, wherein both the side wall surface and the chamfered surface of the end surface of the glass substrate are ground by relatively moving the glass substrate and the grindstone. is there.

  In the conventional grinding process, for example, the outer peripheral side of a cylindrical grindstone is contacted and rotated on the outer peripheral side end surface of the glass substrate. However, in this case, the contact state between the grindstone and the substrate is outside the grindstone. Since this is a line contact in the substrate thickness direction between the radial arc and the outer diameter arc of the substrate, when grinding is performed using a fine abrasive wheel, the load per abrasive grain becomes large, as described above. With the current cutting amount giving priority to the processing efficiency, it is impossible to follow the removal efficiency required for the abrasive grains, resulting in crushing or clogging, and the grinding becomes impossible in a short time. Further, since the abrasive grains that are cutting edges always receive grinding resistance from the same vector direction intermittently, the abrasive grains are severely damaged per unit time.

  On the other hand, in the present invention of configuration 1, the grinding wheel is formed in a cylindrical shape and has a groove shape on the inner peripheral side thereof, and the groove shape corresponds to the side wall surface of the outer peripheral side end surface of the glass substrate. The glass substrate is formed so that both the main surface and the chamfered surface between the side wall surfaces can be ground simultaneously, and the outer peripheral side end surface of the glass substrate is provided on the inner peripheral side of such a grindstone. In order to grind both the side wall surface and the chamfered surface of the end surface of the glass substrate by bringing the glass substrate and the grindstone into contact with each other, the contact state between the grindstone and the substrate in this case is Then, a surface contact state between the inner diameter arc of the grindstone and the outer diameter arc of the substrate occurs, and the contact area between the grindstone and the substrate increases. Because the contact area between the grindstone and the substrate during grinding increases, the contact length (cutting edge length) of the grindstone with the substrate can be increased, thereby reducing abrasive damage per unit time. The sharpness of the abrasive grains can be maintained. Accordingly, even when grinding is performed using a fine abrasive wheel, stable grindability can be ensured, and good grinding surface quality (mirror surface quality) can be stably obtained by grinding mainly of the plastic mode. In addition, by maintaining the sharpness of the grindstone and stably ensuring the grindability for realizing the plastic mode, it is possible to ensure good dimensional shape accuracy by chamfering the end face of the glass substrate.

(Structure 2) The magnetic disk according to Structure 1, wherein grinding is performed by bringing the outer peripheral side end face of the glass substrate into contact with the inner peripheral side of the grindstone and rotating both the glass substrate and the grindstone. This is a method for processing a glass substrate for use.

  In addition to the effects of the invention of Configuration 1, grinding is performed by bringing the outer peripheral side end surface of the glass substrate into contact with the inner peripheral side of the cylindrical grindstone and rotating both the glass substrate and the grindstone as in Configuration 2. Thus, it is possible to prevent the influence of heat during grinding. That is, since the glass material has processing characteristics that are easily affected by the heat generated during the grinding process as described above, in order to enable stable grinding, a grinding liquid ( It is necessary to increase the cooling effect by the coolant and reduce the influence of heat during grinding as much as possible. By contacting the outer peripheral side end surface of the glass substrate with the inner peripheral side of the cylindrical grindstone and rotating both the glass substrate and the grindstone for grinding, the supplied grinding fluid is subjected to centrifugal force acting by the rotation of the grindstone. It becomes easy to stay on the inner surface side of the grindstone, and the grinding fluid always intervenes between the grindstone and the substrate, so that the grinding surface of the grindstone can be effectively cooled, and the sharpness of the fine abrasive grindstone As a result, the influence of heat during grinding can be suppressed and stable grinding can be achieved.

(Structure 3) When the peripheral speed of the said grindstone is set to A and the peripheral speed of the said glass substrate is set to B, the peripheral speed ratio A / B of the said grindstone and the said glass substrate is 30 or more, It is characterized by the above-mentioned. A method for processing a glass substrate for a magnetic disk according to Configuration 2.
As in Configuration 3, in the present invention, the peripheral speed ratio A / B between the grindstone and the glass substrate is particularly preferably 30 or more.

(Configuration 4) As the grindstone, a resin grindstone composed of abrasive grains and a resin, a metal grindstone composed of abrasive grains and a metal binder, a vitrified grindstone composed of abrasive grains and a glassy binder, and a binder thereof were mixed. The method for processing a glass substrate for a magnetic disk according to any one of configurations 1 to 3, wherein a composite grindstone is used.
For chamfering the end face of the glass substrate for magnetic disks as in the present invention, it is preferable to use a resin grindstone or the like as a grinding grindstone.

(Configuration 5) According to any one of Configurations 1 to 4, wherein the glass substrate is ground while being tilted with respect to a groove direction of a groove shape formed on the inner peripheral side of the grindstone. This is a method of processing a glass substrate for a magnetic disk.
As in Configuration 5, by grinding with the glass substrate tilted with respect to the groove direction of the groove shape formed on the inner peripheral side of the grindstone, the trajectory of the grindstone that contacts the end surface of the substrate is constant. Therefore, the convex part of the grindstone abuts and acts at a random position with respect to the end surface of the substrate, so that the damage to the substrate is less, the ground surface can be finished with a higher smoothness, and the grinding blade is a cutting edge. Dispersion of the grinding resistance vector to the grains can reduce damage while maintaining sharpness, thereby further improving the grinding wheel life.

(Structure 6) The method of processing a glass substrate for a magnetic disk according to any one of structures 1 to 5, wherein the end face of the glass substrate is ground and then the end face is mirror-polished.
After grinding the end surface of the glass substrate according to the present invention described above, a step of mirror-polishing the end surface may also be added depending on the required mirror surface quality.

(Structure 7) The glass for magnetic disk according to Structure 6, wherein the mirror polishing is performed by changing a kind of a grindstone and a grinding liquid and a peripheral speed ratio of the grindstone and the glass substrate during the grinding process. A substrate processing method.
After the end surface of the glass substrate according to the present invention is ground, when the end surface is further mirror-polished, the type of the grindstone and the grinding liquid and the peripheral speed ratio of the grindstone and the glass substrate are changed from those during the grinding process. be able to.

(Configuration 8) A method for manufacturing a glass substrate for a magnetic disk, comprising a step of grinding an outer peripheral side end surface of a disk-shaped glass substrate by the processing method according to any one of Configurations 1 to 7. is there.

(Structure 9) A magnetic disk manufacturing method, wherein at least a magnetic layer is formed on the main surface of the magnetic disk glass substrate manufactured by the magnetic disk glass substrate manufacturing method according to Structure 8.

According to the method for processing a glass substrate for a magnetic disk according to the present invention, it is possible to ensure the dimensional shape accuracy of the outer peripheral side end surface of the glass substrate for a magnetic disk from the viewpoint of meeting the demand for higher recording density and lower price of the magnetic disk. It is possible to achieve stable grinding that can be finished efficiently and with high quality at low cost.
In addition, according to the method for manufacturing a glass substrate for a magnetic disk having an end surface grinding process to which this processing method is applied, a glass substrate for a magnetic disk whose end face is finished with high quality is stably provided in large quantities at a low cost. It becomes possible.

  Furthermore, according to the magnetic disk manufacturing method using the magnetic disk glass substrate manufactured by this method of manufacturing a magnetic disk glass substrate, the end surface of the substrate can be finished with high quality, and the end surface of the substrate can be protected against corrosion. It is possible to provide a magnetic disk capable of preventing the occurrence of a failure due to the surface state and realizing further higher recording density.

Hereinafter, the best mode for carrying out the present invention will be described in detail.
[First Embodiment]
FIG. 1 is an overall view of a glass substrate 1 for a magnetic disk to which the present invention is applied, in which (A) is a side view showing a part of the glass substrate in cross section, and (B) is a plan view thereof. The The glass substrate 1 is formed in a disc (disc) shape as a whole with a circular hole at the center, and the front and back main surfaces 11 and 11 and the end face on the outer peripheral side formed between the main surfaces 11 and 11. 12 and an end face 13 on the inner peripheral side.
The end surface 12 on the outer peripheral side of the glass substrate 1 has a side wall surface 12a orthogonal to the main surface 11 and two chamfered surfaces formed between the side wall surface 12a and the front and back main surfaces 11 and 11, respectively. (Chamfered surfaces) 12b and 12b are formed in a shape. The end surface 13 on the inner peripheral side of the glass substrate 1 is also formed between the side wall surface 13a orthogonal to the main surface 11 and between the side wall surface 13a and the main surfaces 11 and 11 on the front and back sides, respectively. Two chamfered surfaces (chamfered surfaces) 13b and 13b are formed.

  In the case of a magnetic disk, for example, a 2.5 inch disk, the glass substrate 1 is finished to have an outer diameter of 65 mm and an inner diameter of 20 mm. Here, the inner diameter is the inner diameter of a circular hole in the center of the glass substrate 1.

  Further, the main surface 11, the outer peripheral side end face 12, and the inner peripheral side end face 13 of the magnetic disk glass substrate 1 are polished (mirror polished) so as to have a predetermined surface roughness. Both the outer peripheral side end surface 12 and the inner peripheral side end surface 13 are finished to the end face shape as described above, and the surface roughness is finished to a mirror surface state with, for example, Rmax of 1 μm or less and Ra of 0.1 μm or less. Is usually required. In the present invention, the surface roughness of the substrate end face is measured using, for example, a Mitutoyo fine contour shape measuring instrument SV-624 with a stylus diameter of 5 μm.

The glass substrate 1 for a magnetic disk is usually a glass substrate (glass disk) 10 formed into a predetermined disk shape by, for example, direct pressing, etc., and sequentially performs processes such as end face grinding, polishing, main surface mirror polishing, and chemical strengthening. Manufactured.
First, the grinding process of the end surface of the glass substrate (glass disk) 10 will be described.

  The method for processing a glass substrate for a magnetic disk according to the present invention is characterized in that the glass is obtained by grinding a contact with a grindstone on an outer peripheral side end surface of the glass substrate while supplying a grinding liquid to an end surface portion of the disk-shaped glass substrate. A method of processing a glass substrate for a magnetic disk for processing an end surface of a substrate, wherein the grindstone is formed in a cylindrical shape and has a groove shape on an inner peripheral side thereof, and the groove shape is formed on the glass substrate. It is formed so that both the side wall surface of the outer peripheral side end surface and the chamfered surface between the main surface and the side wall surface of the glass substrate can be ground simultaneously, and the glass is disposed on the inner peripheral side of the grindstone. It is characterized in that both the side wall surface and the chamfered surface of the end surface of the glass substrate are ground by contacting the outer peripheral side end surface of the substrate and relatively moving the glass substrate and the grindstone. Yes.

  FIG. 2 shows a first embodiment of a method for processing a magnetic disk glass substrate according to the present invention, wherein (A) is a side sectional view of a grinding wheel used for grinding an outer peripheral side end surface of the glass substrate, (B) is a top view which shows the state which grinds the outer peripheral side end surface of the said glass substrate using the said grinding wheel (However, about a grinding wheel, it is a plane sectional view along the II line in (A) figure. Is).

  The grinding wheel 2 used for grinding the outer peripheral side end face of the glass substrate 10 is formed in a cylindrical shape as a whole and has a groove 3 shape on the inner peripheral side thereof. The groove 3 is formed so that both the side wall surface of the outer peripheral side end surface of the glass substrate 10 and the chamfered surface between the main surface and the side wall surface of the glass substrate can be ground simultaneously. Specifically, a groove shape including a side wall portion (side wall surface grinding portion) 3a and chamfer portions (chamfered surface grinding portions) 3b and 3b existing on both sides thereof is provided. The side wall 3a and the chamfered portions 3b and 3b of the groove 3 are formed in a predetermined size and shape in consideration of the target size and shape of the ground surface of the glass substrate 10 to be finished.

  As shown in FIG. 2B, in the present invention, the outer peripheral side end face 12 of the glass substrate 10 is brought into contact with the inner peripheral side of the grinding wheel 2 and the glass substrate 10 and the grinding wheel 2 are relatively moved. Thus, simultaneous grinding of both the side wall surface and the chamfered surface of the outer peripheral side end surface 12 of the glass substrate 10 is performed (note that the glass substrate 10 is not shown in FIG. 2A). .

  In the conventional grinding process, for example, the outer peripheral side of the glass substrate is rotated by contacting the outer peripheral side of a cylindrical grinding wheel, for example. In this case, the contact state between the grindstone and the substrate is as follows. Since this is a line contact between the outer diameter arc and the outer diameter arc of the substrate in the thickness direction of the substrate, for example, when grinding is performed using a fine abrasive wheel that is advantageous for processing surface quality, the load per abrasive grain blade As described above, the current cutting amount giving priority to the machining efficiency cannot follow the removal efficiency required for the abrasive grains, resulting in crushing or clogging, and the grinding becomes impossible in a short time. In addition, since the abrasive grains that are cutting edges always receive grinding resistance from the same vector direction intermittently, the abrasive grains are severely damaged per unit time.

On the other hand, in the present invention, as can be seen with reference to FIG. 2B, the contact state between the grinding wheel 2 and the glass substrate 10 in this case is the inner diameter arc of the grinding wheel 2 and the outer diameter of the substrate 10. A surface contact state with the arc results in an increase in the contact area between the grinding wheel 2 and the substrate 10. By increasing the contact area between the grinding wheel 2 and the substrate 10 at the time of grinding in this way, the contact length (cutting edge length) of the grinding wheel 2 with respect to the substrate 10 is increased, whereby abrasive grains per unit time. Therefore, the sharpness of the abrasive grains can be maintained. Therefore, stable grinding performance can be secured even when grinding is performed using a fine abrasive wheel that is advantageous for machining surface quality, and good grinding surface quality (mirror surface quality) by plastic mode-based grinding is stable. Can get to. In addition, by maintaining the sharpness of the grinding wheel and stably securing the grindability for realizing the plastic mode, it is possible to ensure good dimensional shape accuracy by chamfering the end face of the glass substrate.
In the present invention, the outer peripheral side end surface 12 of the glass substrate 10 is brought into contact with the inner peripheral side of the grinding wheel 2 to grind the end surface of the glass substrate. For example, the outer diameter may be appropriately determined.

  Moreover, in this invention, the grinding | polishing process of a glass substrate end surface is carried out by making the outer peripheral side end surface 12 of the glass substrate 10 contact the inner peripheral side of the grinding wheel 2, and moving the glass substrate 10 and the grinding wheel 2 relatively. For example, in order to increase mass productivity, grinding is performed by bringing the outer peripheral side end face 12 of the glass substrate 10 into contact with the inner peripheral side of the grinding wheel 2 and rotating both the glass substrate 10 and the grinding wheel 2. It is advantageous to do so.

  Thus, in the present invention, by rotating both the glass substrate 10 and the grinding wheel 2 for grinding, in addition to the mass productivity and the effects of the present invention described above, the influence of heat during grinding can be prevented. Is possible. That is, since the glass material has processing characteristics that are easily affected by the heat generated during the grinding process as described above, in order to enable stable grinding, a grinding liquid ( It is necessary to increase the cooling effect by the coolant and reduce the influence of heat during grinding as much as possible. When the outer peripheral side end face 12 of the glass substrate 10 is brought into contact with the inner peripheral side of the cylindrical grinding wheel 2 and both the glass substrate 10 and the grinding wheel 2 are rotated for grinding, the supplied grinding liquid is supplied to the grinding wheel. The centrifugal force acting by the rotation of 2 makes it easy to stay on the inner surface side of the grinding wheel 2, and the grinding liquid always intervenes between the grinding wheel 2 and the substrate 10. Can be cooled, and the sharpness of the grindstone can be maintained when using a fine abrasive grindstone. As a result, the influence of heat during grinding can be suppressed and stable grinding can be performed. Become.

Referring to FIG. 2, the glass substrate 10 has a rotation axis passing through the center O ₁₀ , and the grinding wheel 2 has a rotation axis passing through the center O _2, and the inner peripheral side of the grinding wheel 2 Both the glass substrate 10 and the grinding wheel 2 are rotated while the outer peripheral side end face 12 of the glass substrate 10 is in contact with the glass substrate 10. For example, the substrate holding means that enables the outer peripheral side end face 12 of the glass substrate 10 to contact and separate from the inner peripheral side (groove 3) of the grinding wheel 2 and the glass substrate 10 are driven to rotate in a predetermined direction (for example, two directions). It can be carried out using a grinding apparatus including at least one driving means, a second driving means for rotating the grinding wheel 2 in a predetermined direction (for example, two directions), and a control means.

In this case, in the present invention, the peripheral speeds of the grinding wheel 2 and the glass substrate 10 do not need to be particularly limited. However, from the viewpoint of grindability and processing efficiency, for example, the peripheral speed (A) of the grinding wheel 2 is 600 to 1200 m / min, and the peripheral speed (B) of the glass substrate 10 is preferably about 10 to 20 m / min. Therefore, it is preferable in the present invention that the peripheral speed ratio A / B between the grinding wheel 2 and the glass substrate 10 is 30 or more, preferably 30 to 60.
Note that the rotation direction of the grinding wheel 2 and the glass substrate 10 may be the same direction (counter direction) or a different direction (anti-counter direction).

  As the grinding wheel 2 used in the present invention, a resin grindstone made of abrasive grains and resin can be used. For chamfering the end face of the magnetic disk glass substrate as in the present invention, it is preferable to use a resin grindstone as a grinding grindstone. In addition, a metal grindstone composed of abrasive grains and a metal binder, a vitrified grindstone composed of abrasive grains and a vitreous binder, and a composite grindstone obtained by mixing these binders can also be used. In particular, as a resin grindstone, for example, diamond abrasive grains are added to a suitable filler as necessary, and bonded to a phenol resin, an epoxy resin, a polyethylene resin, a polystyrene resin, a polyimide resin, or the like, and formed into a predetermined shape. Things can be used. Also, alumina abrasive grains, cubic boron nitride abrasive grains, and the like can be used. As the grain size of the abrasive grains, for example, fine abrasive grains of # 1500 or smaller can be suitably used. In the case of the present invention, even when a fine abrasive wheel that is advantageous from the viewpoint of improving the quality of the processed surface is used, the sharpness of the grindstone can be maintained and stable grindability can be ensured, and the good grinding surface quality (mirror surface quality ) And good dimensional shape accuracy can be stably obtained.

  Further, the grinding fluid (coolant) used in the present invention is not particularly limited, but a water-soluble grinding fluid having a high cooling effect and high safety at the production site is particularly suitable.

The glass type used for the magnetic disk glass substrate is not particularly limited. Examples of the glass substrate material include aluminosilicate glass, soda lime glass, soda aluminosilicate glass, aluminoborosilicate glass, borosilicate glass, Examples thereof include glass ceramics such as quartz glass, chain silicate glass, or crystallized glass. Of these, aluminosilicate glass is particularly preferable because it is excellent in impact resistance and vibration resistance. The aluminosilicate _{glass, SiO 2: 62~75wt%, Al} 2 O 3: 5~15wt%, Li 2 O: 4~10wt%, Na 2 O: 4~12wt%, ZrO 2: the 5.5～15Wt% A glass for chemical strengthening or the like having a weight ratio of Na ₂ O / ZrO ₂ of 0.5 to 2.0 and a weight ratio of Al ₂ O ₃ / ZrO ₂ of 0.4 to 2.5 is preferable. In order to eliminate protrusions on the glass substrate surface caused by the undissolved material of ZrO ₂ , SiO ₂ is 57 to 74%, ZnO ₂ is 0 to 2.8%, and Al ₂ O ₃ is 3 in terms of mol%. It is preferable to use glass containing ˜15%, LiO ₂ ˜7-16%, Na ₂ O 4˜14%.

  In addition, although the grinding process of the outer peripheral side end surface of the glass substrate 10 is performed as mentioned above, the grinding process of an inner peripheral side end surface can be implemented by applying the method currently performed normally.

  Moreover, after grinding the outer peripheral side end surface of the glass substrate by the above-mentioned this invention, the process of mirror-polishing an end surface similarly according to the required mirror surface quality may be added. After grinding the end face on the outer peripheral side of the glass substrate according to the present invention, when the same end face is further mirror-polished, for example, the kind of the grindstone and the polishing liquid and the peripheral speed ratio of the grindstone and the glass substrate are determined during the grinding process. Except for changing, it can be performed by the same method as the grinding. That is, the outer peripheral side end face 12 of the glass substrate 10 is brought into contact with the inner peripheral side of a polishing grindstone having a structure similar to that of the grinding grindstone 2 as shown in FIG. 2, and both the glass substrate 10 and the polishing grindstone are rotated to perform mirror polishing. Processing.

As a polishing grindstone in this case, for example, a cerium oxide grindstone, a silicon oxide (silica) grindstone, or the like can be used. As the polishing liquid, a water-soluble polishing liquid containing, for example, cerium oxide or silicon oxide (silica) abrasive grains as an abrasive is suitable.
In this case, the peripheral speed of the polishing grindstone is preferably 50 to 100 m / min, and the peripheral speed of the glass substrate 10 is preferably about 10 m / min. Therefore, the peripheral speed ratio between the polishing grindstone and the glass substrate 10 is preferably 5 or more, more preferably in the range of about 5 to 10.

By grinding the outer peripheral side end face of the glass substrate according to the present invention described above, it is possible to stably obtain good grinding surface quality and good dimensional shape accuracy. The polishing margin is small, and the polishing time can be as short as several tens of seconds, for example, and the work load can be reduced as compared with the prior art.
The glass substrate that has been subjected to the grinding and polishing steps of the outer peripheral side and inner peripheral side end surfaces of the substrate as described above is then subjected to a mirror polishing step, a chemical strengthening step, and the like of the main surface, as shown in FIG. Such a magnetic disk glass substrate 1 is obtained.

According to the method for processing a glass substrate for a magnetic disk according to the present invention, it is possible to ensure the dimensional shape accuracy of the outer peripheral side end surface of the glass substrate for a magnetic disk from the viewpoint of meeting the demand for higher recording density and lower price of the magnetic disk. It is possible to achieve stable grinding that can be finished efficiently and with high quality at low cost.
Therefore, according to the method for manufacturing a glass substrate for magnetic disk having an end surface grinding process to which this processing method is applied, a stable and large amount of glass substrates for magnetic disk whose end surfaces are finished with high quality are provided at low cost. It becomes possible to do.

[Second Embodiment]
FIG. 3 shows a second embodiment of the present invention, in which (A) is a side sectional view showing a state in which the outer peripheral side end face of the glass substrate for magnetic disk is ground using a grinding wheel. B) is a plan view thereof (however, the grinding wheel is a cross-sectional plan view taken along the line II-II in FIG. (A)). In FIG. 3, the same reference numerals are assigned to the same parts as in FIG.

In the present embodiment, in the grinding process of the outer peripheral side end face of the glass substrate 10 in the first embodiment described above, the glass is formed in the groove direction of the groove 3 shape formed on the inner peripheral side of the grinding wheel 2. Grinding is performed with the substrate 10 tilted.
Referring to FIG. 3, the glass substrate 10 has an axis of rotation L ₁₀ passing through the center O _10, the grinding wheel 2 has a rotary shaft L ₂ passing through the center O _2, the grinding wheel 2 tilt state inner peripheral side inclines the glass substrate 10 relative to the grooves formed 3 groove direction shape of, i.e. relative to the rotational axis L ₂ of the grinding wheel 2 the rotational axis L ₁₀ of the glass substrate 10 by an angle α In this state, while the outer peripheral side end face 12 of the glass substrate 10 is in contact with the inner peripheral side of the grinding wheel 2, both the glass substrate 10 and the grinding wheel 2 are rotated to perform grinding.

Thus, the glass substrate 10 is ground with a predetermined angle α, for example, with respect to the groove direction of the groove 3 formed on the inner peripheral side of the grinding wheel 2, so that the end surface of the glass substrate 10 is abutted. The trajectory of the grinding wheel 2 in contact with the grinding wheel 2 is not constant, and the convex portion (abrasive grains) of the grinding wheel 2 abuts and acts on the substrate end surface at random positions. Can be finished with higher smoothness, and the vector of the grinding resistance to the abrasive grains as the cutting edge is dispersed to reduce damage while maintaining the sharpness, thereby further improving the life of the grindstone.
Although the inclination angle α of the glass substrate 10 with respect to the groove direction on the inner peripheral side of the grinding wheel 2 described above can be arbitrarily set, in order to better exhibit the above-described effects, for example, a range of 5 to 30 degrees. It is preferable to be inside.

  The kind of the grinding wheel 2 and the grinding fluid used in the present embodiment may be the same as those in the first embodiment. Further, the peripheral speed and the peripheral speed ratio of each of the grinding wheel 2 and the glass substrate 10 can be made the same as in the case of the first embodiment.

On the other hand, in the grinding process of the inner peripheral side end face 13 of the glass substrate 10, as shown in FIG. 4, the grinding process is performed while the glass substrate 10 is inclined with respect to the groove direction of the groove 5 shape formed in the grinding wheel 4. It is preferable to do.
4A is a side sectional view showing a state where the inner peripheral side end face of the glass substrate for magnetic disk is ground using a grinding wheel, and FIG. 4B is a plan sectional view of the grinding wheel ((A ) Is a cross-sectional plan view taken along line III-III in FIG.

  The grinding wheel 4 used for grinding the inner peripheral side end face of the glass substrate 10 has a groove 5 shape. The groove 5 is formed so that both the side wall surface of the inner peripheral side end surface of the glass substrate 10 and the chamfered surface between the main surface and the side wall surface of the glass substrate can be ground simultaneously. Specifically, it has a groove shape including a side wall portion (side wall surface grinding portion) 5a and chamfer portions (chamfered surface grinding portions) 5b, 5b existing on both sides thereof.

Referring to FIG. 4, the glass substrate 10 is tilted with respect to the groove direction of the groove 5 formed in the grinding wheel 4, that is, the glass substrate 10 is rotated with respect to the rotation axis L ₄ of the grinding wheel 4. In a state where the axis L ₁₀ is inclined by an angle β, the grinding wheel 4 is brought into contact with the inner peripheral side end face 13 of the glass substrate 10, and both the glass substrate 10 and the grinding wheel 4 are rotated for grinding.

  Thus, the outer peripheral side end surface of the glass substrate is obtained by grinding the inner peripheral side end surface while the glass substrate 10 is inclined, for example, by a predetermined angle β with respect to the groove direction of the groove 5 shape of the grinding wheel 4. As in the case of this grinding process, there is little damage to the substrate, the ground surface can be finished with higher smoothness, and there is also an effect of improving the life of the grindstone.

Although the inclination angle β of the glass substrate 10 with respect to the groove direction of the grinding wheel 4 can be arbitrarily set, in order to better exhibit the above-described effects, as in the case of grinding of the outer peripheral side end face. For example, it is preferable to be within a range of 5 to 30 degrees.
In addition, what is necessary is just to use the thing similar to the case of the grinding process of the above-mentioned outer peripheral side end surface as the kind of the grinding wheel 4 used for the grinding process of an inner peripheral side end surface, and a grinding fluid. Further, the peripheral speed and the peripheral speed ratio of each of the grinding wheel 4 and the glass substrate 10 may be appropriately set so as to be suitable for the grinding of the inner peripheral side end face.

According to another aspect of the present invention, there is provided a magnetic disk manufacturing method comprising: forming at least a magnetic layer on a main surface of a magnetic disk glass substrate manufactured by the above-described method for manufacturing a magnetic disk glass substrate according to the present invention. Also provide.
That is, a magnetic disk can be obtained by forming at least a magnetic layer on the glass substrate for a magnetic disk obtained by the first or second embodiment of the present invention. Usually, for example, a magnetic disk in which an adhesion layer, a soft magnetic layer, an underlayer, a magnetic layer, a protective layer, a lubricating layer, and the like are provided on a glass substrate is preferable.

As the magnetic layer, for a perpendicular magnetic recording medium, for example, an alloy having a Co-based hcp crystal structure may be used. The magnetic layer may be used for a perpendicular magnetic recording medium or an in-plane magnetic recording medium.
As a protective layer, a carbon-type protective layer etc. are mentioned preferably, for example. Examples of the lubricant that forms the lubricating layer on the protective layer include PFPE (perfluoropolyether) compounds.
As a method for forming each of the layers on the glass substrate, a known sputtering method or the like can be used. A plasma CVD method is also preferably used for forming the carbon-based protective layer. A dipping method or the like can be used for forming the lubricating layer.

  According to the magnetic disk manufacturing method using the magnetic disk glass substrate manufactured by the method for manufacturing a magnetic disk glass substrate according to the present invention, the end surface of the substrate can be finished with high quality, and the end surface of the substrate can be protected against corrosion. It is possible to provide a magnetic disk capable of preventing the occurrence of a failure due to the surface state and realizing further higher recording density.

Hereinafter, the embodiment of the present invention will be described more specifically with reference to examples. In addition, this invention is not limited to a following example.
Example 1
(1) Rough lapping step (rough grinding step), (2) Fine lapping step (fine grinding step), (3) End surface grinding step (4) End surface polishing step, (5) Main surface first polishing step, ( The glass substrate for a magnetic disk of this example was manufactured through 6) the main surface second polishing step and (7) the chemical strengthening step.

(1) Coarse lapping step First, a glass substrate (glass disk) made of disc-shaped aluminosilicate glass having a diameter of 66 mmφ and a thickness of 1.0 mm is obtained from molten glass by direct pressing using an upper die, a lower die, and a barrel die. It was. In this case, in addition to the direct press, a disk-shaped glass substrate may be obtained by cutting out with a grinding wheel from a sheet glass formed by a downdraw method or a float method. As the aluminosilicate _glass, SiO 2: 58 to 75 _{wt%, Al} 2 O 3: _{5~23 wt%,} Li 2 O: _{3~10 wt%,} Na 2 O: _4~13 chemical containing wt% Tempered glass was used. Next, a lapping process was performed on the glass substrate in order to improve dimensional accuracy and shape accuracy. This lapping process was performed using a double-sided lapping machine and using abrasive grains having a particle size of # 400. Specifically, first, using alumina abrasive grains of particle size # 400, setting the load to about 100 kg and rotating the sun gear and the internal gear of the lapping device, both surfaces of the glass substrate housed in the carrier are faced. Lapping was performed with an accuracy of 0 to 1 μm and a surface roughness (Rmax) of about 6 μm.

(2) Fine lapping step Next, the grain size of the abrasive grains was changed to # 1000 and the surface of the glass substrate was lapped so that the surface roughness was about 2 μm in Rmax and about 0.2 μm in Ra. The glass substrate after the lapping process was sequentially immersed in each washing bath (application of ultrasonic waves) of neutral detergent and water to perform ultrasonic cleaning.

(3) End surface grinding step Next, a hole is made in the central portion of the glass substrate using a cylindrical grindstone, and the outer peripheral side end surface of the substrate is ground by the method shown in FIG. Then, a predetermined chamfering process was performed on the outer peripheral side end face. The grinding wheel used in this case was formed by bonding diamond abrasive grains having a particle size of # 3000 with a phenol resin and molding the diamond abrasive grains into a predetermined cylindrical shape as shown in FIG. A predetermined groove shape was formed on the inner peripheral side of the grinding wheel. A water-soluble grinding fluid (temperature 20 ° C.) was used as the grinding fluid.
By supplying the grinding liquid to the outer peripheral side end surface portion of the glass substrate, bringing the outer peripheral side end surface of the glass substrate into contact with the inner peripheral side of the grinding wheel and rotating both the glass substrate and the grinding wheel Both the side wall surface and the chamfered surface of the outer peripheral side end surface were ground. The peripheral speed of the grindstone was 1500 m / min, and the peripheral speed of the glass substrate was 50 m / min (thus, the peripheral speed ratio between the grindstone and the glass substrate was 30).

Thus, grinding was performed for about 30 seconds. The surface roughness of the outer peripheral side end surface of the glass substrate at this time was about 0.5 μm in Rmax for both the side wall surface and the chamfered surface. In general, a 2.5-inch HDD (hard disk drive) uses a magnetic disk having an outer diameter of 65 mm.
Next, the inner peripheral side end face of the substrate was ground and chamfered using a predetermined grinding wheel as in the conventional case.

(4) End surface grinding | polishing process Subsequently, the outer peripheral side end surface of the glass substrate was grind | polished. A cerium oxide grindstone with a particle size of 1.2 μm is used as the grinding wheel, and a cerium oxide slurry is used as the grinding liquid. The peripheral speed of the grindstone is 100 m / min, and the peripheral speed of the glass substrate is 10 m / min. 10), except that the outer peripheral side end face was ground by the method shown in FIG. The polishing time was about 12 seconds.
Next, the inner peripheral side of the glass substrate was polished using a conventional polishing brush and polishing apparatus. In this case, the material of the bristle of the polishing brush was 6-6 nylon. The rotational speed of this polishing brush was 1400 rpm, and the rotational speed of the glass substrate was 60 rpm in the direction opposite to that of the polishing brush. Further, cerium oxide was used as the polishing agent, and a polishing liquid at about 30 ° C. containing this cerium oxide was supplied.

The surface roughness of the end face on the outer peripheral side of the glass substrate after finishing the 100 grinding and polishing processes in this way was finished to a mirror surface with an average value of Ra of about 0.05 μm. When the end face shape of the outer peripheral side of the polished glass substrate was measured with a tracer, the end face 12 was finished in a predetermined chamfered shape composed of two chamfered faces 12b and a side wall face 12a therebetween as shown in FIG. It was. The inner peripheral side end face was also finished in almost the same shape. The variation in the angular shape of the side wall surface and the chamfered surface of the outer peripheral side end surface is within ± 0.8 ° with respect to 45 degrees, the variation in the outer diameter is also within 10 μm, and the dimensional shape accuracy of the outer peripheral side end surface Was good. Further, in the end face observation after the polishing finish, the remaining processing damage was observed on the entire outer peripheral end face using a microscope (magnification × 200), but the residual trace was not confirmed, and the polishing face was good. In addition, the grinding wheel used above did not have a problem such as clogging or crushing, and maintained a good sharpness even after the processing.
Further, the average surface roughness Ra of the inner peripheral side end face of the glass substrate was about 0.05 μm, and the dimensional variation of the inner diameter was within 10 μm.
And the surface of the glass substrate which finished the said end surface grinding | polishing process was washed with water.

(5) Main surface first polishing step Next, a first polishing step was performed using a double-side polishing apparatus in order to remove scratches and distortions remaining in the lapping step described above. In a double-side polishing apparatus, a glass substrate held by a carrier is brought into close contact with an upper and lower surface plate to which a polishing pad is attached, the carrier is engaged with a sun gear and an internal gear, and the glass substrate is sandwiched between upper and lower surface plates. Press. Thereafter, a polishing liquid is supplied and rotated between the polishing pad and the polishing surface of the glass substrate, whereby the glass substrate revolves while rotating on the surface plate to simultaneously polish both surfaces. Specifically, a polishing process was performed using a hard polisher (hard urethane foam) as a polisher. The polishing conditions were RO water in which cerium oxide (average particle size 1.3 μm) was dispersed as a polishing agent as a polishing liquid, a load: 100 g / cm ² , and a polishing time: 15 minutes. The glass substrate after the first polishing step was sequentially immersed in each cleaning bath of neutral detergent, pure water, pure water, IPA (isopropyl alcohol), and IPA (steam drying), ultrasonically cleaned, and dried. .

(6) Main surface second polishing step Next, using the same type of double-side polishing apparatus as that used in the first polishing step, the polisher was changed to a soft polisher (suede pad), and the second polishing step was performed. This second polishing step is intended to reduce, for example, the surface roughness Ra to about 1.0 to 0.3 μm or less while maintaining the flat surface obtained in the first polishing step. is there. The polishing conditions were RO water in which cerium oxide (average particle size 0.8 μm) was dispersed as a polishing liquid, a load: 100 g / cm ² , and a polishing time of 5 minutes. The glass substrate after the second polishing step was sequentially immersed in each cleaning bath of neutral detergent, pure water, pure water, IPA, and IPA (steam drying), ultrasonically cleaned, and dried.

(7) Chemical strengthening process Next, the glass substrate which finished the said washing | cleaning was chemically strengthened. For chemical strengthening, a chemical strengthening solution in which potassium nitrate and sodium nitrate were mixed was prepared, the chemical strengthening solution was heated to 380 ° C., and the cleaned and dried glass substrate was immersed for about 4 hours to perform chemical strengthening treatment. The glass substrate after chemical strengthening was sequentially immersed in each of washing tanks of sulfuric acid, neutral detergent, pure water, pure water, IPA, and IPA (steam drying), ultrasonically cleaned, and dried.
Next, a visual inspection of the glass substrate surface after the cleaning and a precision inspection using light reflection / scattering / transmission were performed. As a result, no defects such as protrusions and scratches due to deposits were found on the glass substrate surface. Further, when the surface roughness of the main surface of the glass substrate obtained through the above steps was measured with an atomic force microscope (AFM), a glass substrate for magnetic disk having an ultra-smooth surface with Ra = 0.20 nm was obtained. Obtained. The glass substrate had an outer diameter of 65 mm, an inner diameter of 20 mm, and a plate thickness of 0.635 mm.

  As described above, about 10,000 glass substrates for magnetic disks were manufactured and a long run test was performed. As a result, the average ratio of non-defective products that cleared the specified end face shape, dimensional accuracy, and surface roughness by the first end face grinding and polishing process is 90% or more on average. Most of them were.

Next, using the glass substrate for magnetic disk obtained above, the following adhesion layer, soft magnetic layer, first underlayer, second underlayer are formed on the main surface using a single-wafer sputtering apparatus. Then, a magnetic layer was sequentially formed, then a carbon-based protective layer was formed by a plasma CVD method, and a lubricating layer was further formed thereon by a dip method to obtain a magnetic disk.
For the adhesion layer, a Ti-based alloy thin film was formed to a thickness of 100 mm. For the soft magnetic layer, a Co-based alloy thin film was formed to a thickness of 600 mm. As the first underlayer, a Pt-based alloy thin film was formed to a thickness of 70 mm, and as the second underlayer, a Ru alloy thin film was formed to a thickness of 400 mm. The magnetic layer was made of a CoPtCr alloy and had a thickness of 200 mm. The protective layer was a diamond-like carbon protective layer. In addition, an alcohol-modified perfluoropolyether lubricant was used for the lubricating layer.
The magnetic disk thus obtained is a magnetic disk for perpendicular magnetic recording.

  The obtained magnetic disk was mounted on a load unload (LUL) HDD (hard disk drive). As the magnetic head, a magnetic head provided with a giant magnetoresistive effect reproducing element (GMR element) was used, and the flying height of the magnetic head was 10 nm. When the LUL endurance test in which the load / unload operation of the head was repeated in a high-temperature and high-humidity environment of 70 ° C. and 80% RH in the environment of the HDD was conducted, the magnetic disk of this example has a LUL of 1 million times. Durable without failure in operation. Also, no flying stiction trouble occurred.

(Example 2)
In the grinding process and the polishing process of the outer peripheral side end face of the glass substrate in Example 1, the rotation axis of the substrate was inclined 15 degrees (α = 15 degrees) with respect to the groove direction of the grindstone according to the method shown in FIG. In this state, both the side wall surface and the chamfered surface of the outer peripheral side end surface of the glass substrate are ground by bringing the outer peripheral side end surface of the glass substrate into contact with the inner peripheral side of the grindstone and rotating both the glass substrate and the grindstone. processed. In this case, the peripheral speeds of the grindstone and the glass substrate were the same as those in Example 1.

The surface roughness of the end face on the outer peripheral side of the glass substrate that had been subjected to 100 grinding and polishing processes in this way was finished to a mirror surface with an average value of Ra of about 0.02 μm. When the end face shape of the outer peripheral side of the polished glass substrate was measured with a tracer, the end face 12 was finished in a predetermined chamfered shape composed of two chamfered faces 12b and a side wall face 12a therebetween as shown in FIG. It was. The inner peripheral side end face was also finished in almost the same shape. The variation in the angular shape of the side wall surface and the chamfered surface of the outer peripheral side end surface is within ± 0.8 ° with respect to 45 degrees, the variation in the outer diameter is also within 10 μm, and the dimensional shape accuracy of the outer peripheral side end surface Was good. Further, in the end face observation after the polishing finish, the remaining processing damage was observed on the entire outer peripheral end face using a microscope (magnification × 200), but the residual trace was not confirmed, and the polishing face was good. In addition, the grinding wheel used above did not have a problem such as clogging or crushing, and maintained a good sharpness even after the processing.
Further, the average surface roughness Ra of the inner peripheral side end face of the glass substrate was about 0.05 μm, and the dimensional variation of the inner diameter was within 10 μm.
Except for the above, a magnetic disk glass substrate was produced in the same manner as in Example 1.

  As a result of manufacturing about 10,000 glass disk substrates for magnetic disks and performing a long run test as described above, the non-defective product that has cleared the specified end face shape, dimensional accuracy, and surface roughness by the first end face grinding and polishing process. The rate was 90% or more on average, and most of the substrates that were defective became good products by re-polishing.

Next, using the magnetic disk glass substrate obtained above, a magnetic disk was produced in the same manner as in Example 1.
The obtained magnetic disk was subjected to the same LUL durability test as in Example 1. As a result, the magnetic disk of this example was durable without failure in the LUL operation of 1 million times. Also, no flying stiction trouble occurred.

(Comparative example)
This comparative example is different from the above-described embodiment in that the grinding of the outer peripheral side end surface of the glass substrate is performed using a conventional method. That is, grinding was performed by bringing the outer peripheral surface of the glass substrate into contact with the outer peripheral surface of the cylindrical grinding wheel and rotating both the glass substrate and the grindstone. A diamond grindstone (or cerium oxide grindstone) having a particle size (fine abrasive grain # 500) was used as the grinding wheel. Other grinding conditions were adjusted as appropriate.
Subsequently, the outer peripheral side end surface of the glass substrate was polished using a conventional polishing brush and polishing apparatus. In this case, the material of the bristle of the polishing brush was 6-6 nylon. The polishing agent used was cerium oxide, and a polishing liquid containing about 30 ° C. containing cerium oxide was supplied. Other polishing conditions were adjusted as appropriate.

A glass substrate for a magnetic disk was manufactured in the same manner as in Example 1 except for the above points.
The surface roughness of the end face on the outer peripheral side of the glass substrate after finishing the grinding and polishing of 100 sheets in this way was an average value of Ra of about 0.1 μm, but the dimensional variation of the outer diameter was as large as about 50 μm.
When the end face shape of the outer peripheral side of the polished glass substrate was measured with a tracer, the end face 12 was finished in a predetermined chamfered shape composed of two chamfered faces 12b and a side wall face 12a therebetween as shown in FIG. It was. And the dispersion | variation in the angular shape of the side wall surface and chamfering surface of an outer peripheral side end surface was as large as +/- 5 degree with respect to 45 degree | times, and the angular shape precision of the outer peripheral side end surface was not favorable. In addition, for grinding of the outer peripheral side end surface, a fine abrasive wheel that is advantageous in terms of processing surface quality was used, but problems such as clogging and crushing occurred in a short time. It was necessary to set conditions, and work efficiency was reduced.

  Also in this comparative example, about 10,000 of the 2.5-inch magnetic disk glass substrate was manufactured and a long run test was performed. As a result of the first end face grinding and polishing, a predetermined end face shape and dimensions were obtained. The percentage of non-defective products that cleared the angular accuracy and surface roughness was 80% or less on average.

1 shows a glass substrate for a magnetic disk according to the present invention, in which (A) is a side view showing a part of the glass substrate and (B) is a plan view thereof. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a first embodiment of the present invention, where (A) is a side sectional view of a grinding wheel used for grinding an outer peripheral side end surface of a magnetic disk glass substrate, and (B) is the above-described grinding wheel. It is a top view (partial plane sectional view) which shows the state which grinds the outer peripheral side end surface of a glass substrate. The 2nd Embodiment of this invention is shown, (A) is a sectional side view which shows the state which grinds the outer peripheral side end surface of the glass substrate for magnetic discs using a grinding wheel, (B) is the It is a top view (partial plane sectional view). (A) is a sectional side view showing a state where the inner peripheral side end face of the glass substrate for magnetic disk is ground using a grinding wheel, and (B) is a plan sectional view of the grinding wheel.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Glass substrate for magnetic discs 2 Outer peripheral end grinding wheel 4 Inner peripheral end grinding grindstone 3, 5 Groove

10 Disc-shaped glass substrate (glass disc)
11 Main surface 12 of glass substrate Outer peripheral side end surface 12a of glass substrate Side wall surface 12b Chamfered surface 13 Inner peripheral side end surface of glass substrate

Claims (8)

A method for processing a glass substrate for a magnetic disk, wherein an end surface of a glass substrate is processed by grinding a contact surface on an outer peripheral side end surface of the glass substrate while supplying a grinding liquid to an end surface portion of the disk-shaped glass substrate. Because
The grindstone is formed in a cylindrical shape and has a groove shape on the inner peripheral side thereof. The groove shape includes a side wall surface of the outer peripheral side end surface of the glass substrate, a main surface and a side wall surface of the glass substrate. The chamfered surface is formed so that both surfaces can be ground simultaneously, the outer peripheral side end surface of the glass substrate is brought into contact with the inner peripheral side of the grindstone at one location, and the inner peripheral side of the grindstone The side wall surface and the chamfer of the end surface of the glass substrate are moved in a state in which the glass substrate is inclined with respect to the groove direction of the groove shape formed on the glass substrate and the grindstone. A method for processing a glass substrate for a magnetic disk, comprising grinding both surfaces.   2. The glass substrate for a magnetic disk according to claim 1, wherein grinding is performed by bringing an outer peripheral side end face of the glass substrate into contact with an inner peripheral side of the grindstone and rotating both the glass substrate and the grindstone. Processing method.   The peripheral speed ratio A / B between the grindstone and the glass substrate is 30 or more, where A is the peripheral speed of the grindstone and B is the peripheral speed of the glass substrate. The processing method of the glass substrate for magnetic discs of description.   As the grindstone, a resin grindstone composed of abrasive grains and a resin, a metal grindstone composed of abrasive grains and a metal binder, a vitrified grindstone composed of abrasive grains and a vitreous binder, and a composite grindstone obtained by mixing these binders are used. The method for processing a glass substrate for a magnetic disk according to any one of claims 1 to 3, wherein: After grinding the end face of the glass substrate, likewise processing method for a glass substrate according to any one of claims 1 to 4 to the end face, characterized in that mirror polishing. 6. The processing of a glass substrate for a magnetic disk according to claim 5 , wherein the mirror polishing is performed by changing a kind of a grindstone and a grinding liquid and a peripheral speed ratio of the grindstone and the glass substrate at the time of the grinding. Method. A method for producing a glass substrate for a magnetic disk, comprising a step of grinding an outer peripheral side end surface of a disk-shaped glass substrate by the processing method according to any one of claims 1 to 6 . A method for manufacturing a magnetic disk, comprising forming at least a magnetic layer on a main surface of the glass substrate for a magnetic disk manufactured by the method for manufacturing a glass substrate for a magnetic disk according to claim 7 .

Images