JP2014180709A - Manufacturing method of grindstone, and glass substrate for magnetic disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grindstone which grinds an end surface shape of a disk-shaped substrate highly accurately into a target shape.SOLUTION: A grindstone 12 comes into contact with an end surface 10b on an outer circumferential side of a disk-shaped substrate 10 in the state where a rotational axis Y is inclined with respect to a normal direction X of a main surface of the disk-shaped substrate 10 having a pair of main surfaces which is an object to be processed, and performs grinding of the end surface. A cross-sectional shape of the grindstone 12 which contacts the end surface 10b on a grinding surface, which is formed by cutting on a plane including the rotational axis Y, is a concave shape toward the rotational axis Y. A grinding surface of the grindstone 12 is provided for a columnar outer surface, and an end surface 10b on the outer circumferential side of the glass substrate 10 is ground by using the grindstone 12.

Description

  The present invention relates to a rotating grindstone for grinding a disk-shaped substrate and a method for manufacturing a glass substrate for a magnetic disk using the rotating grindstone.

  A glass substrate is suitably used for a magnetic disk used as one of information recording media. Today, in response to a request for an increase in storage capacity in a hard disk drive device, the density of magnetic recording has been increased. Along with this, the magnetic recording information area is miniaturized by extremely shortening the flying distance from the magnetic recording surface of the magnetic head. In such a magnetic disk, in order to stabilize reading and writing by the magnetic head, it is required to improve the roundness of the outer peripheral end face and the roundness of the circular hole provided in the magnetic disk.

  By the way, in the end face grinding of a disk-shaped substrate to be processed such as a disk-shaped glass substrate, the grinding disclosed in Patent Document 1 is performed in order to improve the processing efficiency of the grinding and the life of the rotating grindstone used for the grinding. It has been broken. The grinding disclosed in Patent Document 1 is a state in which the rotation axis of the rotating grindstone is inclined with respect to the normal direction of the main surface of the disk-shaped substrate (the rotation axis of the disk-shaped substrate and the rotation axis of the grinding wheel are the same plane). A grinding process in which a disk-shaped end face is brought into contact with the end face to grind the end face. The grinding disclosed in Patent Document 1 has little damage to the glass substrate, small surface roughness and in-plane variation of the ground surface, can make the ground surface smoother, and can improve the life of the grindstone. It is a grinding suitable for the point.

JP 2000-167753 A

However, as a result of performing end surface grinding of the outer peripheral side end surface of the disk-shaped substrate by the grinding method disclosed in Patent Document 1, the target shape can be obtained with high accuracy on the outer peripheral side end surface of the disk-shaped substrate after grinding. There wasn't.
Accordingly, the present invention provides a rotating grindstone that can grind the shape of the outer peripheral side end face of a disc-shaped substrate to a target shape with high accuracy in end face grinding of a disc-shaped substrate, and a glass for a magnetic disk using the rotating grindstone. An object is to provide a method for manufacturing a substrate.

  The inventor of the present application observed the end face shape of the disc-shaped substrate after variously grinding the outer peripheral end surface of the disc-shaped substrate using the above grinding method, and the outer peripheral side end surface of the disc-shaped substrate was orthogonal to the main surface. The present invention finds that the central portion in the thickness direction of the substrate is not a shape to be concave but is a concave shape.

In one embodiment of the present invention, the rotation axis is inclined with respect to the normal direction of the main surface of the disk-shaped substrate having a pair of main surfaces to be processed, and the end surface on the outer peripheral side of the disk-shaped substrate is contacted. A rotating grindstone for grinding the end face in contact,
A cross-sectional shape of the grinding surface of the rotating grindstone that comes into contact with the end surface when cut along a plane including the rotating shaft is a concave shape toward the rotating shaft.

  The concave shape is preferably an arc shape. The concave shape may be an elliptical arc shape or a parabolic shape.

  At this time, it is preferable that the rotating grindstone has a cylindrical shape, and the grinding surface of the rotating grindstone is provided on the outer surface of the columnar shape.

In another aspect of the present invention, an outer peripheral end surface that grinds an outer peripheral side end surface of the disk-shaped substrate, which is the disk-shaped substrate, using the rotary grindstone as a grinding wheel for grinding an outer peripheral end surface. A method for manufacturing a glass substrate for a magnetic disk including a grinding process, wherein in the outer peripheral side end face grinding process, the outer peripheral side end face of the base plate is ground using the rotating grindstone.
In other words, another aspect of the present invention is a method for manufacturing a magnetic disk glass substrate including an end surface grinding process for grinding an end surface of a magnetic disk glass base plate that is a disk-shaped substrate having a circular hole in the center. In the end face grinding process, the outer peripheral end face of the magnetic disk glass base plate is ground using the rotary grindstone.

  At this time, an inner peripheral side end surface grinding process is performed in which the inner peripheral side end surface of the base plate in the circular hole portion at the center of the magnetic disk base plate is ground using a cylindrical inner peripheral end surface grinding rotary grindstone. In addition, in the inner peripheral side end surface grinding process, the inner peripheral side end surface of the base plate is ground using the cylindrical outer surface, and the inner peripheral side of the grinding surface of the inner peripheral side end surface grinding rotary grindstone It is preferable that the cross-sectional shape when cut along a plane including the rotation axis of the rotating grindstone for end face grinding is a convex shape toward the inner peripheral side end face of the base plate.

  In the above-described rotating grindstone and the method for producing a glass substrate for a magnetic disk using the rotating grindstone, the end face shape of the disk-shaped substrate can be formed with high accuracy into a target shape.

(A), (b) is a figure explaining the grinding performed with respect to the outer peripheral side end surface of the glass substrate using the rotary grindstone of this embodiment. (A) is a figure explaining the cross-sectional shape of the rotary grindstone of this embodiment, (b) is a figure explaining the end surface shape of the glass substrate after the end surface grinding of this embodiment. (A) is a figure explaining the cross-sectional shape of the conventional rotary grindstone, (b) is a figure explaining the end surface shape of the glass substrate after the conventional end surface grinding. It is a figure explaining the grinding using the rotating grindstone performed with respect to the inner peripheral side end surface of a glass substrate. It is a figure explaining the cross-sectional shape of the rotating grindstone performed with respect to the inner peripheral side end surface of a glass substrate.

  Hereinafter, the manufacturing method of the glass substrate for magnetic discs which is the rotary grindstone of this invention and a disk shaped board | substrate is demonstrated in detail.

(Outline of end face grinding used in this embodiment)
In the present embodiment, in the normal direction of the main surface of the base plate of the magnetic disk glass substrate (magnetic disk base plate) having a circular hole in the center, which is a disk-shaped substrate having a pair of main surfaces to be processed. On the other hand, in a state where the rotation axis of the rotating grindstone is inclined, the end face (outer end face) orthogonal to the main surface of the base plate is brought into contact with the end face to be ground. Thereby, an end surface (hereinafter referred to as a side wall surface) orthogonal to the main surface of the base plate is formed. In the rotary grindstone that performs such end face grinding, the cross-sectional shape of the surface to be ground that comes into contact with the end face of the base plate (the cross-sectional shape when cut along the plane including the rotation axis of the rotary grindstone) is It has a concave shape. In other words, the grinding surface of the rotating grindstone when cut along a plane including the rotating shaft of the rotating grindstone has a concave shape that is recessed toward the rotating shaft. By grinding using such a rotating grindstone, the shape of the side wall surface after grinding can be accurately orthogonal to the main surface. When the grinding is performed, the rotation axis of the rotating grindstone is inclined so that the axis orthogonal to the main surface of the base plate and the rotating shaft of the rotating grindstone are in a twisted relationship with each other.

  As described above, when the outer peripheral side end surface of the disk-shaped substrate is ground when the cross-sectional shape of the bottom of the groove of the rotating grindstone is a linear shape, a side wall surface orthogonal to the main surface is formed. The inventor of the present application has found that a surface having a concave concave central portion in the substrate thickness direction is formed on the end face of the power plate. For this reason, in order to make this concave shape into a linear shape, the cross-sectional shape of the groove bottom portion of the rotating grindstone is a concave shape that is dented toward the side wall surface of the substrate. In addition, it is preferable that the concave shape of the groove bottom part in a rotating grindstone is circular arc shape at the point which can orthogonally cross the side wall surface of a board | substrate with a main surface with high precision.

Hereinafter, the manufacturing method will be described in detail by taking a base plate of a magnetic disk glass substrate as an example of a disk-shaped substrate.
In addition, in this invention, the glass substrate for magnetic discs means what the grinding process concerning this invention was given. Specifically, for example, the glass substrate for a magnetic disk according to the present invention may be one immediately after being subjected to grinding, and after grinding, main surface polishing, chemical strengthening The film may be in a state before being subjected to post-processing such as before the magnetic film or the like is formed.

An example of the manufacturing method of the disk shaped substrate of the present embodiment, that is, the manufacturing method of the glass substrate for magnetic disk will be described below.
First, a glass blank as a material for a plate-like glass substrate for a magnetic disk having a pair of main surfaces is formed. Next, this glass blank is appropriately processed, a circular hole is formed in the central portion, and a disk-shaped glass substrate (base plate) that is subjected to end face grinding so that the edge of the main surface of the circular hole and the outer peripheral portion is chamfered. Is made. Thereafter, the main surface is polished. Note that the polishing process may be performed in a plurality of processes as necessary. In addition, the end face (including the chamfered portion) may be polished before the polishing process. Moreover, you may perform the grinding process of the main surface of a glass substrate before a grinding | polishing process. At this time, the order of each process may be determined as appropriate. Hereinafter, each process will be described.

(A) Glass blank forming treatment In forming a glass blank, for example, a press forming method can be used in addition to the float method. Furthermore, it can manufacture using well-known manufacturing methods, such as a downdraw method, a redraw method, and a fusion method. A disk-shaped glass blank serving as a base of the magnetic disk glass substrate is cut out by appropriately performing shape processing on the plate-shaped glass produced by these known manufacturing methods.

(B) Shape processing processing Next, shape processing processing is performed. In the shape processing, a disk-shaped glass substrate (element plate) having a circular hole is obtained by forming a circular hole using a known processing method after the glass blank forming process. Thereafter, further chamfering is performed. The chamfering is performed by, for example, a total shape grindstone using diamond abrasive grains. Thereby, a side wall surface orthogonal to the main surface and a chamfered surface connecting the side wall surface and the main surface are formed on the end surface of the glass substrate (element plate). Further, the shape processing includes end face grinding described later. The end surface grinding is performed on the end surface of the base plate. The end surface grinding is performed such that the rotary grindstone that contacts the end surface of the base plate does not have the same position. This grinding will be described later. By this shape processing of the glass substrate, the glass substrate becomes a magnetic disk glass substrate (hereinafter, the magnetic disk glass substrate is referred to as a glass substrate).

(C) End face polishing process Next, the end face polishing process of the glass substrate obtained by the shape processing process is performed. The end surface polishing process is a process for performing polishing by supplying a polishing liquid containing loose abrasive grains between the polishing brush and the end surface of the glass substrate and relatively moving the polishing brush and the glass substrate. In the end surface polishing, the inner peripheral side end surface and the outer peripheral side end surface of the glass substrate are in a mirror state. At this time, a slurry containing fine particles such as cerium oxide as free abrasive grains is used. By performing the end surface polishing, it is possible to remove contamination such as dust, foreign matter particles such as dust on the end surface of the glass substrate, damage, or scratches. Thereby, generation | occurrence | production of thermal asperity can be prevented. Further, from the viewpoint of preventing the occurrence of ion precipitation that causes corrosion such as sodium and / or potassium, polishing is performed so that at least the surface roughness (Rz) of the side wall surface is 0.15 μm or less. Is preferable, and it is more preferable to polish so as to be 0.10 μm or less. Moreover, in the said viewpoint, it is preferable that the surface roughness (Ra) of at least a side wall surface is 0.015 micrometer or less, and it is more preferable that it is 0.010 micrometer or less. The roughness is measured using a stylus meter (measurement distance: 0.25 mm in the plate thickness direction).

(D) First polishing treatment Next, a first polishing treatment is performed on the main surface of the glass substrate. Specifically, the main surfaces on both sides of the glass substrate are polished while holding the glass substrate in a holding hole provided in a holding member (carrier) attached to the double-side polishing apparatus. In addition, in order to further reduce the surface roughness or perform more precise adjustment, the first polishing process may be divided into a plurality of polishing processes.

(E) Chemical strengthening treatment The glass substrate can be appropriately chemically strengthened. As the chemical strengthening liquid, for example, a molten liquid obtained by heating potassium nitrate, sodium nitrate, or a mixture thereof can be used. Then, by immersing the glass substrate in the chemical strengthening solution, lithium ions and sodium ions in the glass composition on the surface of the glass substrate are converted into sodium ions and potassium ions having relatively large ion radii in the chemical strengthening solution, respectively. By replacing each, a compressive stress layer is formed in the surface layer portion, and the glass substrate is strengthened.
The timing of performing the chemical strengthening treatment can be determined as appropriate. However, if the polishing treatment is performed after the chemical strengthening treatment, the foreign matter fixed to the surface of the glass substrate by the chemical strengthening treatment can be removed together with the smoothing of the surface. This is particularly preferable because it can be performed.

(F) Second Polishing (Final Polishing) Process Next, a second polishing process is performed on the glass substrate after the chemical strengthening process. Also in the second polishing, a double-side polishing apparatus having the same configuration as the double-side polishing apparatus used for the first polishing is used. After the second polishing, the glass substrate is washed to produce a magnetic disk glass substrate.

(Grinding of the outer edge of the glass substrate)
FIGS. 1A and 1B are diagrams illustrating grinding using a rotating grindstone 12 performed on an outer peripheral side end surface of a disk-shaped glass substrate 10 which is a base plate. FIG. 2A is a view for explaining the cross-sectional shape of the groove 12c of the rotary grindstone 12, and FIG. 2B is a view for explaining the end face shape of the glass substrate 10 after end face grinding. The rotary grindstone 12 is a rotary grindstone used for grinding the outer peripheral side end face of the glass substrate. In FIG. 1A and FIG. 2A, the size of the groove 12c and the thickness of the glass substrate 10 are shown relatively larger than the size of the rotating grindstone 12 for easy understanding.

As shown in FIG. 1 (a), the rotating grindstone 12 used for grinding the outer peripheral side end face of the glass substrate 10 is formed in a cylindrical shape as a whole, and as shown in FIG. 2 (a), a side wall 12a. And a groove 12c formed of chamfered portions 12b and 12b existing on both sides thereof. In other words, in the rotating grindstone 12, grinding grooves for grinding are formed on the surface of a cylindrical rotating body. Of the grinding grooves, the groove 12c is formed so that both the side wall surface 10a and the chamfered surface 10b of the outer peripheral side end surface of the glass substrate 10 can be ground simultaneously. Specifically, the side wall portion 12a grinds the side wall surface 10a, and the chamfered portions 12b and 12b grind the chamfered surfaces 10b and 10b. The side wall portion 12a and the chamfered portion 12b of the groove 12c are formed in a predetermined dimensional shape in consideration of the target dimensional shape of the ground surface of the glass substrate 10.
In grinding of the outer peripheral side end surface of the glass substrate 10, as shown in FIG. 1A, the glass substrate 10 is inclined with respect to the groove direction of the groove 12 c formed in the rotating grindstone 12, that is, the glass substrate 10. Grinding is performed by bringing the outer peripheral side end face of the glass substrate 10 into contact with the rotating shaft 14 extending in the rotating shaft direction Y of the rotating grindstone 12 with respect to the normal direction X of the main surface by an inclination angle α. As a result, the position of the grinding point on the grinding surface of the rotating grindstone 12 that contacts the outer peripheral end surface of the glass substrate 10 is not fixed at the same position in the rotation axis direction of the rotating grindstone 12, so Even if there is a portion, the outer peripheral side end surface of the glass substrate 10 is not always scratched at the same position in the rotation axis direction. For this reason, damage to the glass substrate 10 can be reduced. Moreover, the surface roughness of the side wall surface and the chamfered surface of the glass substrate and the in-plane variation thereof can be reduced. It is possible to finish the ground surface to a higher level, that is, to a level of quality that can meet higher quality requirements. Furthermore, it has an effect of improving the life of the grindstone as compared with the case where grinding is performed without tilting the conventional rotating shaft in the normal direction of the glass substrate.

The above-mentioned inclination angle α can be arbitrarily set, but in order to better exhibit the above-described effects, it is preferably within a range of 1 to 30 degrees, for example, within a range of 5 to 15 degrees. More preferably, it is more preferably in the range of 2 to 10 degrees.
Although it does not specifically limit as an abrasive grain of the rotary grindstone 12 used for grinding, From a viewpoint of a processing speed, it is preferable to use a diamond abrasive grain. An electrodeposition grindstone in which diamond abrasive grains are electrodeposited and a resin bond grindstone in which diamond abrasive grains are bonded with a resin (resin) can be suitably used.
When an electrodeposition grindstone is used as the rotating grindstone 12 used for grinding, it is preferable because the grinding speed can be improved. From the viewpoint of improving the grinding speed, the count of the diamond grindstone that is an electrodeposited grindstone is preferably # 300 to # 800.
When a resin bond grindstone is used as the rotating grindstone 12 used for grinding, it is preferable because the surface roughness of the end surface (chamfered surface, side wall surface) of the glass substrate by grinding can be further improved. At this time, the count of the diamond grindstone is preferably # 2000 to # 3000 from the viewpoint of improving the end face quality after the grinding process and reducing the load of the end face polishing process.
For example, the peripheral speed of the rotating grindstone 12 when grinding is preferably in the range of 800 to 1000 m / min. Moreover, the peripheral speed of the glass substrate 10 is preferably within a range of 5 to 20 m / min. The ratio of the peripheral speed of the rotating grindstone 12 to the peripheral speed of the glass substrate 10 (peripheral speed ratio) is preferably in the range of 80 to 200 in order to improve the end face quality of the glass substrate by grinding.

  The side wall portion 12a of the rotating grindstone 12, that is, the grinding surface of the rotating grindstone 12 that comes into contact with the side wall surface 10a of the glass substrate 10, has a cross-sectional shape when it is cut by a plane including the rotating shaft 14 to be ground. The concave shape is concave with respect to the glass substrate 10 side (concave shape toward the rotating shaft 14). The concave shape is formed with, for example, a smooth curved shape shown in FIG. 2A, and is preferably formed with an arc shape or a parabolic shape. The outer surface of the cylindrical rotating grindstone 12 is a grinding surface, and the side wall surface of the glass substrate 10 in the case where grinding is performed with the circular shape of the rotating grindstone 12 and the circular shape of the glass substrate 10 being circumscribed is performed. The preferable radius of curvature of the arc shape of the grinding surface of the rotating grindstone 12 to be ground is appropriately set according to the outer diameter of the glass substrate 10, the inner diameter of the rotating grindstone 12, the inclination angle α, and the degree of orthogonality to the main surface of the side wall surface. do it. Specifically, for example, when the outer diameter of the glass substrate 10 is in the range of 50 mm to 150 mm, the outer diameter of the rotating grindstone 12 is 10 to 20 mm, and the inclination angle α is 1 to 15 degrees, The radius of curvature of the arc shape having the concave shape of the grinding surface is preferably within a range of 10 to 700 mm.

A side wall surface extending in a direction orthogonal to the main surface 10c of the glass substrate 10 as shown in FIG. 2B by grinding the outer peripheral side end surface of the glass substrate 10 using such a rotating grindstone 12. 10a can be formed.
FIGS. 3A and 3B are views for explaining the cross-sectional shape of the groove 102c of the conventional rotating grindstone 102 and the end surface shape of the glass substrate 100 after conventional end surface grinding.
As shown in FIG. 3A, the side wall 102 a of the rotating grindstone 102, that is, the surface to be ground of the rotating grindstone 102 that comes into contact with the surface 100 a of the glass substrate 100 was cut by a plane including the rotation axis of the rotating grindstone 102. The cross-sectional shape at the time is a linear shape. And the surface 100a corresponding to the side wall surface of the glass substrate 100 which performed the grinding | polishing process of the outer peripheral side end surface using this rotating grindstone 102 has comprised the concave shape dented with respect to the rotating grindstone 102 side. The reason why such a shape is formed is that grinding is performed by placing the outer peripheral side end surface of the glass substrate 100 in contact with the outer surface of the rotating grindstone 102, that is, so as to circumscribe. The inventor of the present application has found this point, and in order to form a side wall surface extending in a direction orthogonal to the main surface 10 c of the glass substrate 10, the idea is that the side wall portion of the rotating grindstone is made concave in advance. Yes.

  In this embodiment, since the groove 12c has the side wall portion 12a and the chamfered portion 12b, the side wall surface 10a and the chamfered surfaces 10b and 10b of the glass substrate 10 can be ground simultaneously. For example, when grinding only the side wall surface 10a of the glass substrate 10, the rotating grindstone 12 may not have the chamfered portion 12b.

Thus, when the outer peripheral side end face of the glass substrate 10 is ground according to the present invention, the surface to be ground of the rotary grindstone 12 that comes into contact with the outer peripheral side end face of the glass substrate 10 is the rotational axis 14 of the rotary grindstone 12. The cross-sectional shape when cut by the plane including the surface forms a concave shape (concave shape recessed toward the rotation axis of the rotating grindstone 12) with respect to the end surface of the glass substrate 10. For this reason, the side wall surface 10a in which the end surface of the glass substrate 10 is orthogonal to the main surface 10c of the glass substrate 10 can be formed. That is, the end surface shape of the glass substrate 10 can be formed with high accuracy into a target shape.
In this embodiment, when the side wall surface of the outer peripheral side end surface of the glass substrate 10 is ground (contacted) with the outer surface of the rotating grindstone 12, the center of the glass substrate 10 and the rotation axis of the rotating grindstone 12 are the glass substrate. Grinding is performed so that each of the circumference of the rotating grindstone 12 and the circumference of the glass substrate exists on the opposite side when viewed from the grinding point where the side wall surface of 10 and the grinding surface of the rotating grindstone 12 abut. . In other words, the center of the glass substrate 10 and the rotation axis of the rotating grindstone 12 exist at a position sandwiching the grinding point. In this case, by making the shape of the grinding surface of the rotating grindstone 12 the concave shape, the shape of the side wall surface of the outer peripheral side end surface of the glass substrate 10 can be accurately orthogonal to the main surface.
In addition, the rotating grindstone according to the present invention is such that the end surface (10a and 10a and 10b), the side wall surface 10a constituting the end surfaces (10a and 10b) and the intervening surface (chamfered surface 10b) interposed between the side wall surface 10a and the main surface 10c are ground. It is a rotary grindstone for processing, and is inclined with respect to a bottom portion 12a for grinding the side wall surface 10a of the outer peripheral side end surface and a bottom portion 12a connected to the bottom portion 12a and for grinding the interposition surface. The bottom portion 12a has a concave cross section in the plane including the rotation axis with respect to the outside of the grindstone (the end surfaces (10a and 10b) of the glass substrate 10) (abrasion). The recessed toward the axis of rotation) may be configured as a concave shape.
That is, when the outer peripheral side end face of the glass substrate 10 is ground using the rotating grindstone 12, the rotation axis of the rotating grindstone 12 sandwiches the center of the glass substrate 10 (center of the circular hole 10d) and the grinding point. Will be in position. In this case, by making the shape of the grinding surface of the rotating grindstone 12 the concave shape, the shape of the side wall surface of the outer peripheral side end surface of the glass substrate 10 can be accurately orthogonal to the main surface. In other words, the shape of the rotating grindstone 12 is a cylindrical shape and a grinding groove is formed on the outer surface thereof, and the rotating shaft of the rotating grindstone 12 and the center of the glass substrate 10 face each other with a grinding point interposed therebetween. If it is in the position to be used, the shape of the grinding surface of the rotating grindstone 12 is the above concave shape, so that the shape of the side wall surface of the outer peripheral side end surface of the glass substrate 10 can be accurately orthogonal to the main surface. it can.
This completes the description of the grinding of the outer peripheral side end face and the rotary grindstone used for this grinding. Furthermore, the grinding | polishing of the inner peripheral side end surface of a glass substrate and the rotating grindstone used for this grinding are given and demonstrated about the example of a preferable form.

(Grinding of the inner surface of the glass substrate)
FIG. 4 is a diagram illustrating grinding using the rotating grindstone 22 performed on the inner peripheral side end face of the glass substrate 10 which is a base plate. FIG. 5 is a view for explaining the cross-sectional shape of the rotating grindstone 22. The rotating grindstone 22 is a rotating grindstone used for grinding the inner peripheral side end face of the glass substrate.

The rotating grindstone 22 is formed in a cylindrical shape as a whole, and has a side wall 22a and a groove 22c including chamfered portions 22b and 22b existing on both sides thereof as shown in FIG. The groove 22c is formed so that both the side wall surface 10a and the chamfered surface 10b of the inner peripheral side end surface of the circular hole 10d provided in the glass substrate 10 can be ground simultaneously. Specifically, the side wall portion 22a grinds the side wall surface 10a, and the chamfered portions 22b and 22b grind the chamfered surfaces 10b and 10b. The side wall portion 22a and the chamfered portion 22b of the groove 22c are formed in a predetermined dimensional shape in consideration of the target dimensional shape of the ground surface of the glass substrate 10.
In the grinding of the inner peripheral side end face of the glass substrate 10, as in the grinding of the outer peripheral side end face, the glass substrate 10 is tilted with respect to the groove direction of the groove 22 c formed in the rotating grindstone 22, that is, the main glass substrate 10. With the rotation axis (not shown) extending in the rotation axis direction of the rotating grindstone 22 inclined by the inclination angle α with respect to the normal direction of the surface, the inner peripheral side end surface of the glass substrate 10 is brought into contact with the inner periphery. Grind side end faces. In this case, the grinding surface of the rotating grindstone 22 is inscribed in the inner peripheral side end surface of the glass substrate 10. As a result, the position of the rotating grindstone 12 that contacts the inner peripheral side end surface of the glass substrate 10 is not fixed at the same position in the rotation axis direction of the rotating grindstone 12, so that even if there are minute convex portions on the circumference of the rotating grindstone 12. In the same position in the rotation axis direction of the outer peripheral side end face of the glass substrate 10, there is always no scratch. For this reason, damage to the glass substrate 10 can be reduced. Moreover, the surface roughness of the side wall surface and the chamfered surface of the glass substrate and the in-plane variation thereof can be reduced. It is possible to finish the ground surface to a higher level, that is, to a level of quality that can meet higher quality requirements. Furthermore, it has an effect of improving the life of the grindstone as compared with the case where grinding is performed without tilting the conventional rotating shaft in the normal direction of the glass substrate.

  In addition, what is necessary is just to make it the same as that of the rotating grindstone 12 mentioned above about the inclination angle at the time of grinding the inner peripheral side end surface which is a circular hole of the glass substrate 10 using the rotating grindstone 22. As shown in FIG.

And the side wall part 22a of the rotating grindstone 22, that is, the grinding surface of the rotating grindstone 22 that comes into contact with the side wall surface 10a of the glass substrate 10, has a cross-sectional shape when cut by a plane including the rotation axis of the rotating grindstone 22, It is convex toward the glass substrate 10 side. In other words, the cross-sectional shape of the grinding surface when cut along a plane including the rotation axis of the rotating grindstone 22 is a shape (convex shape) protruding in a direction perpendicular to the rotation axis of the rotating grindstone 22. The convex shape is formed, for example, in a smooth curved shape, but is preferably formed in an arc shape or a parabolic shape. The preferred radius of curvature of the arc shape of the grinding surface of the rotating grindstone 22 for grinding the side wall surface of the glass substrate 10 when the outer surface of the rotating grindstone 22 and the glass substrate 10 are in contact with each other so as to be inscribed is as follows. The outer diameter of the glass substrate 10, the outer diameter of the rotating grindstone 22, the inclination angle α, and the degree of orthogonality to the main surface of the side wall surface may be set as appropriate. Specifically, for example, when the inner diameter of the glass substrate 10 is in the range of 10 mm to 20 mm, the outer diameter of the rotating grindstone 22 is 5 to 18 mm, and the inclination angle α is 1 to 15 degrees, the grinding of the rotating grindstone 22 is performed. The radius of curvature of the arc shape of the surface is preferably in the range of 6 to 300 mm.
That is, when the outer surface of the rotating grindstone 22 is brought into contact (inscribed) with the side wall surface of the inner peripheral end surface of the circular hole 10d of the glass substrate 10, the center of the glass substrate 10 and the rotating shaft of the rotating grindstone 12 are ground. However, it is ground so that it exists on the same side of the circumference of the rotating grindstone 12 and the circumference of the glass substrate as seen from the grinding point where the side wall surface of the glass substrate 10 and the grinding surface of the rotating grindstone 12 abut. Processing is in progress.

By grinding the inner peripheral side end face in the circular hole 10d of the glass substrate 10 using such a rotating grindstone 22, the side wall surface 10a extending in the direction orthogonal to the main surface 10c of the glass substrate 10 is set on the inner peripheral side. It can be formed on the end face.
Although the groove 22c of the rotating grindstone 22 has the side wall portion 22a and the chamfered portion 22b, the chamfered portion 22b may not be provided. For example, when performing end surface grinding that does not have a chamfered surface on the inner peripheral side end surface, the chamfered portion 22b is not required.

[Experimental example]
In order to confirm the effect of the outer peripheral end face of the present embodiment, the outer peripheral end face of the glass substrate was ground by grinding under two different conditions (Example and Conventional Example).
A disk-shaped glass substrate (element plate) having an outer diameter of 65 mm, an inner diameter of 20 mm, and a thickness of 0.8 mm was used as the glass substrate to be polished. The circular hole of the glass substrate was provided so that the center of the glass substrate coincided with the center of the circular hole, and the inner diameter of the circular hole was 20 mm.

In the embodiment and the conventional example, the rotating grindstone uses a cylindrical grindstone as shown in FIG. 1A, uses the outer surface of the rotating grindstone as a surface to be ground, and uses the outer surface of the rotating grindstone as a grinding surface. The outer peripheral side end face of was ground. The outer diameter of the grindstone was 15 mm, and the depth of the groove was 1 mm.
The inclination angle α in the example and the conventional example was 10 degrees.
The cross-sectional shape of the side wall portion of the rotating grindstone used in the examples was a concave shape formed of an arc shape having a curvature radius of 34 mm. On the other hand, the cross-sectional shape of the side wall portion of the rotary grindstone used in the conventional example was a linear shape.

With the contents of the above examples and conventional examples, the side wall surface of the glass substrate (element plate) was ground, and the shape of the end surface of the glass substrate was observed.
As a result, the cross-sectional shape of the side wall surface of the glass substrate obtained by grinding of the example was a linear shape, and a side wall surface orthogonal to the main surface of the glass substrate was obtained. On the other hand, the surface corresponding to the side wall surface of the glass substrate obtained by the grinding of the conventional example is a curved shape having a concave cross section as shown in FIG. 3B, and the side wall surface orthogonal to the main surface of the glass substrate is It was not obtained.
From this, the effect of this embodiment is clear.

  As mentioned above, although the manufacturing method of the rotary grindstone of this invention and the glass substrate for magnetic discs was demonstrated in detail, this invention is not limited to the said embodiment and Example, In the range which does not deviate from the main point of this invention, it is various improvement. Of course, you may make changes.

10, 100 Glass substrate 10a Side wall surface 10b Chamfered surface 10c Main surface 10d Circular holes 12, 22, 102 Rotating grindstones 12a, 22a, 102a Side wall portions 12b, 22b Chamfered portions 12c, 22c Groove 14 Rotating shaft 100a surface

Claims (4)

Grinding the end surface by bringing it into contact with the outer peripheral end surface of the disk-shaped substrate in a state where the rotation axis is inclined with respect to the normal direction of the main surface of the disk-shaped substrate having a pair of main surfaces to be processed A rotating grindstone for processing,
The rotary grindstone is characterized in that a cross-sectional shape of the rotating grindstone of the rotating grindstone that comes into contact with the end surface when cut along a plane including the rotating shaft is concave toward the rotating shaft.   The rotating grindstone according to claim 1, wherein the concave shape is an arc shape. The rotating grindstone has a cylindrical shape,
The rotating grindstone according to claim 1 or 2, wherein a grinding surface of the rotating grindstone is provided on an outer surface of the columnar shape. A method for producing a glass substrate for a magnetic disk including an end surface grinding process for grinding an end surface of a glass base plate for a magnetic disk, which is a disk-shaped substrate having a circular hole in the center,
In the said end surface grinding process, the outer peripheral end surface of the said glass base plate for magnetic discs is ground using the rotary grindstone of any one of Claims 1-3, The glass substrate for magnetic discs characterized by the above-mentioned. Manufacturing method.

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