JPWO2017115871A1 - Annular glass substrate, method for producing annular glass substrate, method for producing annular glass substrate, and method for producing glass substrate for magnetic disk - Google Patents

Abstract

In the process of forming an annular glass base plate from a plate-like glass base plate, the first circular blade is rotated at a first turning radius along the main surface with respect to the main surface of the plate-like glass base plate. An outer cut line is formed, and the second circular blade is rotated along the main surface with a second turning radius shorter than the first turning radius to form the inner cut line. A plurality of first cutouts are provided on the cutting edge of the first circular blade at a first interval in the circumferential direction, and a plurality of second cutouts are provided on the cutting edge of the second circular blade. Are provided at a second interval in the circumferential direction. The first interval is smaller than the second interval. The concentricity between the inner peripheral end face and the outer peripheral end face of the annular glass base plate is 15 μm or less. The difference between the roundness of the outer peripheral shape of the first main surface of the annular glass base plate and the roundness of the outer peripheral shape of the second main surface opposite to the first main surface is 100 μm or less. is there.

Description

  The present invention relates to an annular glass base plate, an annular glass base plate manufacturing method, an annular glass substrate manufacturing method, and a magnetic disk glass substrate manufacturing method.

  Today, a personal computer, a DVD (Digital Versatile Disc) recording device, and the like have a built-in hard disk device (HDD: Hard Disk Drive) for data recording. In a hard disk device, a magnetic disk having a magnetic layer provided on a substrate is used, and magnetic recording information is recorded on or read from the magnetic layer by a magnetic head slightly floated on the surface of the magnetic disk. As the substrate of this magnetic disk, a glass substrate having a property that is less likely to be plastically deformed than a metal substrate (aluminum substrate) or the like is preferably used.

  The glass substrate for a magnetic disk is manufactured by preparing an annular glass base plate from a plate-like glass base plate and subjecting the annular glass base plate to mechanical processing such as grinding and polishing. For example, a method of cutting a plate-shaped glass base plate formed by a float method, a downdraw method, etc. into an annular shape, and a glass plate by pressing a lump of molten glass with a pair of press molds A method of cutting a base plate into an annular shape is known.

  For example, a method is known in which a circular cut line is formed on a glass plate, and then a region outside the cut line of the glass plate is heated to cut out a region inside the cut line in a circular shape (Patent Literature). 1). To form an annular glass base plate, a circular incision for forming an outer shape and a circular incision for forming an inner hole are formed on one main surface of the plate-like glass base plate. Thereafter, these cut lines are grown to cleave the plate-like glass base plate, thereby forming an annular glass base plate.

Japanese Patent No. 2973354

  In order to produce an annular glass base plate, a circular outline forming cut (outer cut) and a circular inner hole forming cut (on the main surface of one of the plate-like glass base plates ( In the case of forming an inner incisor), an outer cutter wheel for forming an outer incisor and an inner cutter wheel for forming an inner incisor are pressed against one main surface of a plate-like glass base plate. The cutter wheel and the plate-shaped glass base plate are relatively rotated. At this time, there is a problem that the roundness of the outer incisor deteriorates and the concentricity of the outer incisor and the inner incisor decreases. If the concentricity between the outer and inner incisors is low, it is necessary to increase the machining allowance in order to ensure the concentricity of the outer peripheral shape of the magnetic disk glass substrate and the inner hole. There is a problem of getting worse.

Also, after rotating both the cutter wheel and the plate-shaped glass base plate relative to each other and then heating the outer part of the plate-like glass base plate, the inner cut line is caused by the difference in thermal expansion. It grows and reaches the other main surface (second main surface) opposite to the one main surface (first main surface). Thereafter, by removing the glass other than the target portion, it is possible to take out the annular glass base plate from the plate-like glass base plate. Thereafter, the inner peripheral edge and the outer peripheral edge of the annular glass base plate are chamfered by grinding with a general-purpose grindstone or the like, thereby having a chamfered surface and a side wall surface on the inner periphery and the outer periphery, respectively. An annular glass substrate is formed.
In this case, for example, when forming the outer incision and the inner incision with respect to a plate-shaped glass base plate having a small linear expansion coefficient, the outer incision and the inner incision A phenomenon was observed in which the angles extending from the first main surface in the depth direction differed. More specifically, with respect to the direction (angle) extending in the depth direction of the outer cut line and the inner cut line formed in a circle on the first main surface of the plate-shaped glass base plate, the direction of the inner cut line is A phenomenon of tilting toward the center of the circle rather than the direction of the outer incisor was observed.
Thus, when the direction (angle) in the depth direction of the outer cut line and the inner cut line is formed so as to be different from the first main surface, grinding residue may occur in the substrate after the chamfering process. is there. For this reason, it is necessary to increase the machining allowance during the chamfering process, and there is a problem that the production efficiency of the glass substrate is deteriorated. Moreover, when the outer and inner cut lines are extended to the opposite side of the glass base plate to cleave the plate-like glass base plate, the unnecessary glass portion removal process itself cannot be performed well, resulting in poor production efficiency. There is a problem.

  The present invention is an annular glass base plate capable of increasing the processing efficiency of the glass base plate to increase the production efficiency of the glass substrate, a manufacturing method of the annular glass base plate, a manufacturing method of the annular glass substrate, And it aims at providing the manufacturing method of the glass substrate for magnetic discs.

  The present invention includes the following forms.

(1)
The plate-like glass is formed by forming outer and inner incisors on the surface of the plate-like glass base plate, and causing the outer and inner incisors to advance in the thickness direction of the plate-like glass base plate. An annular glass base plate manufacturing method for forming an annular glass base plate from a base plate,
While pressing the first circular blade against the main surface of the plate-shaped glass base plate, the first circular blade and the plate-shaped glass base plate with a first turning radius along the main surface While forming the outer incisor by rotating relatively,
A second rotation radius that is smaller than the first rotation radius along the main surface while pressing the second circular blade against the main surface of the plate-like glass base plate. And forming the inner cut line by rotating relative to the plate-like glass base plate,
On the cutting edge of the first circular blade, a plurality of first cutouts are provided at a first interval in the circumferential direction,
A plurality of second cutouts are provided on the cutting edge of the second circular blade at a second interval in the circumferential direction,
The method for producing an annular glass base plate, wherein the first interval is smaller than the second interval.
The first interval is preferably 5 to 40 μm. The second interval is preferably 10 to 80 μm.
The maximum depth of the first notch is preferably 3 to 15 μm.
The outer incisor and the inner incisor can be formed separately, but productivity and concentricity can be improved by forming them simultaneously.
The circumferential interval, length, and depth of the cutouts of the first and second circular blades can be appropriately selected according to the rotation radius of the first and second circular blades. As the radius of rotation of the circular blade increases, it is preferable to decrease the notch interval, increase the length of the notch, and increase the depth of the notch.

(2)
The length of the circumferential direction of the said 1st notch is a manufacturing method of the annular | circular shaped glass base plate as described in (1) longer than the circumferential direction length of a said 2nd notch.
The circumferential length of the first notch is, for example, 5 to 60 μm.

(3)
The length of the circumferential direction of the said 1st notch is a manufacturing method of the annular | circular shaped glass base plate as described in (1) or (2) longer than the said 1st space | interval.

(4)
The cutting edge ridge of the first circular blade has a first inner inclined surface closer to the rotation center than the first plane including the cutting edge ridge line of the first circular blade, and the first flat surface with respect to the first flat surface. Formed by a first outer inclined surface opposite to the rotation center;
The cutting edge ridge of the second circular blade has the second inner inclined surface closer to the rotation center than the second plane including the cutting edge ridge line of the second circular blade, and the second plane. Formed by a second outer inclined surface opposite to the rotation center;
An angle between the first inner inclined surface and the first plane is θi1,
An angle formed by the first outer inclined surface and the first plane is θo1,
An angle formed by the second inner inclined surface and the second plane is θi2,
An angle between the second outer inclined surface and the second plane is θo2,
θi1−θo1 = Δθ1,
When defined as θi2−θo2 = Δθ2,
The first circular blade and the second circular blade are:
Δθ2> 0 and Δθ1 <Δθ2
Satisfy the relationship
When forming the outer incisor and the inner incisor,
The first circular blade and the second circular handle are brought into contact with the main surface so that an angle formed with the main surface of the first plane is the same as an angle formed with the main surface of the second plane. The manufacturing method of the annular | circular shaped glass base plate as described in any one of (1)-(3).

(5)
Including a process of shape-processing an end face of the annular glass base plate manufactured by the method for manufacturing an annular glass base plate according to any one of (1) to (4) above. A method of manufacturing a glass substrate for a magnetic disk.

(6)
An annular glass base plate that is an element of an annular glass substrate,
The glass base plate has an inner peripheral end face made of a circular hole in the center, and an outer peripheral end face,
A concentricity between the inner peripheral end surface and the outer peripheral end surface is a glass base plate of 15 μm or less.

(7)
An annular glass base plate that is an element of an annular glass substrate,
A first main surface and a second main surface opposite to the first main surface;
The glass base plate, wherein a difference between the roundness of the outer peripheral shape of the first main surface and the roundness of the outer peripheral shape of the second main surface is 100 μm or less.

(8)
Outer and inner incisors are formed on the main surface of a plate-like glass base plate made of a glass material having a linear expansion coefficient of 65 × 10 ⁻⁷ / ° C. or less, and the outer incisors and the inner incisors are connected to the plate. A method for producing an annular glass base plate including a shape processing treatment for forming an annular glass base plate from the plate-like glass base plate by proceeding in the thickness direction of the glass base plate,
The shape processing is
The first circular blade and the second circular blade brought into contact with one main surface of the plate-like glass base plate are relatively rotated around the main surface and one rotation center, whereby the first Forming a circular outer cutting line on the main surface with one circular blade, and forming a circular inner cutting line on the main surface with a smaller radius than the outer cutting line with the second circular blade. ,
The cutting edge ridge of the first circular blade has a first inner inclined surface closer to the rotation center than the first plane including the cutting edge ridge line of the first circular blade, and the first flat surface with respect to the first flat surface. Formed by a first outer inclined surface opposite to the rotation center;
The cutting edge ridge of the second circular blade has the second inner inclined surface closer to the rotation center than the second plane including the cutting edge ridge line of the second circular blade, and the second plane. Formed by a second outer inclined surface opposite to the rotation center;
An angle between the first inner inclined surface and the first plane is θi1,
An angle formed by the first outer inclined surface and the first plane is θo1,
An angle formed by the second inner inclined surface and the second plane is θi2,
An angle between the second outer inclined surface and the second plane is θo2,
θi1−θo1 = Δθ1,
When defined as θi2−θo2 = Δθ2,
The first circular blade and the second circular handle are:
Δθ2> 0 and Δθ1 <Δθ2
Satisfy the relationship
The first circular blade and the second circular handle are brought into contact with the main surface so that an angle formed with the main surface of the first plane is the same as an angle formed with the main surface of the second plane. A method for producing an annular glass base plate characterized by comprising:

(9)
The manufacturing method of the annular | circular shaped glass base plate as described in (8) which is (theta) i1 <(theta) i2.

(10)
The method for manufacturing an annular glass base plate according to (8) or (9), wherein θi1 + θo1 <θi2 + θo2.

(11)
The annular shape according to any one of (8) to (10), wherein a radius of a circular orbit for rotating the second circular blade relative to the plate-like glass base plate is 20 mm or less. Manufacturing method of glass base plate.

(12)
The manufacturing method of the annular | circular shaped glass base plate as described in any one of (8)-(11) which performs the shape processing process of a plate-shaped glass base plate whose linear expansion coefficient is 50 * 10 < ^-7 > / degreeC or less. .

(13)
(8)-(12) manufacture of the annular | circular shaped glass substrate including the process which shape-processes the end surface of the annular | circular shaped glass base plate manufactured by the manufacturing method of the annular | circular shaped glass base plate as described in any one of (12). Method.

(14)
The method for manufacturing a glass substrate for magnetic disk, wherein the annular glass substrate according to (13) is a glass substrate for magnetic disk.

(15)
An annular glass base plate,
The glass base plate has an inner peripheral end face made of a circular hole in the center, and an outer peripheral end face,
The glass base plate, wherein each of the inner peripheral end surface and the outer peripheral end surface includes a split cross section, and a difference in angle with respect to a main surface of each of the inner peripheral end surface and the outer peripheral end surface is 10 ° or less in a cross-sectional view.

According to the present invention, the roundness of the outer cut line formed by the first circular blade can be improved, and the concentricity between the inner cut line and the outer cut line formed by the second circular blade can be increased. Can be increased. For this reason, the concentricity of the outer peripheral end surface consisting of the split cross-section extending from the outer cut and the inner peripheral end surface consisting of the split cross-section extending from the inner cut can be increased. Therefore, it is possible to reduce the machining allowance in subsequent processes such as chamfering processing and end surface polishing processing on the outer peripheral end surface and the inner peripheral end surface, and it is possible to increase the processing efficiency of the annular glass base plate. The production efficiency of a glass substrate such as a magnetic disk glass substrate can be increased.
Further, according to the present invention, by forming the outer peripheral end surface and the inner peripheral end surface of the annular glass base plate used for manufacturing the glass substrate in substantially the same direction (angle) with respect to the main surface, The processing efficiency of the glass base plate can be increased, and further, the production efficiency of an annular glass substrate, for example, a magnetic disk glass substrate can be increased.

It is an elevation view which shows an example of the scribing apparatus which cuts out an annular | circular shaped glass base plate from a plate-shaped glass base plate. It is an enlarged view which shows an example in the form in 1st Embodiment of the outer cutter wheel shown in FIG. FIG. 3 is a cross-sectional view taken along the line III-III in FIG. 2. FIG. 4 is a view taken along arrow IV in FIG. 2. It is an enlarged view which shows an example in the form in 1st Embodiment of the inner side cutter wheel shown in FIG. It is VI-VI arrow sectional drawing of FIG. It is a VII arrow line view of FIG. It is a perspective view which shows an example of the annular | circular shaped glass base plate 10B. It is an enlarged view which shows an example in the form in 2nd Embodiment of the outer cutter wheel shown in FIG. It is an enlarged view which shows an example in the form in 2nd Embodiment of the inner side cutter wheel shown in FIG. It is a figure which shows an example of the cross section of the annular | circular shaped glass base plate obtained by 2nd Embodiment.

  Hereinafter, the manufacturing method of the glass substrate for magnetic disks which concerns on embodiment of this invention is demonstrated in detail. In addition, the glass substrate used by this embodiment is not limited to the glass substrate for magnetic discs, It can apply to various annular | circular shaped glass substrates. The size of the magnetic disk glass substrate applied as an example in the present embodiment is not particularly limited. For example, a nominal 2.5 inch size (outer diameter of about 65 mm, circular hole diameter of about 20 mm). It is suitable for manufacturing the above glass substrate for magnetic disk. A nominal 3.5-inch size (outer diameter of about 95 mm, circular hole diameter of about 25 mm) or more is more preferable because the effect of reducing the machining allowance becomes larger. Moreover, although it does not restrict | limit especially regarding plate | board thickness, For example, it is suitable for manufacture of the glass substrate for 0.4-2.0 mm magnetic disks.

(Magnetic disk glass substrate)
First, the glass substrate for magnetic disks will be described. The glass substrate for magnetic disks has a disk shape. The glass substrate for magnetic disk has a circular central hole concentric with the outer periphery. A magnetic disk is formed by forming magnetic layers (recording areas) in the annular areas on both sides of the glass substrate for a magnetic disk.

(Glass base plate for magnetic disk)
The glass base plate for a magnetic disk is an annular glass base plate before a polishing process described later is performed. Annular means having a substantially circular outer shape and having a substantially circular inner hole. Here, “substantially circular” includes a perfect circle shape and an ellipse shape, and its outer peripheral shape may consist only of a single arc of curvature radius, or consist of arcs or curves of different curvature radii. It may be.

  In the present embodiment, as will be described later, a circular outer shape forming outer cut line and a circular inner hole forming inner cut line are formed on one main surface (scribe surface) of a plate-like glass base plate. (Scribing). Thereafter, these cut lines are grown to the other main surface to cleave the plate-like glass base plate, thereby forming an annular glass base plate (cleaving treatment).

  A plate-shaped glass base plate can be formed by, for example, cutting a plate glass formed by a float method or an overflow downdraw method into a predetermined size. Moreover, you may form a disk-shaped glass base plate by press-molding a molten glass lump.

  As the material of the glass base plate, aluminosilicate glass, soda lime glass, borosilicate glass, or the like can be used. In particular, aluminosilicate glass can be suitably used in that it can be chemically strengthened and a glass substrate for a magnetic disk excellent in the flatness of the main surface and the strength of the substrate can be produced.

Here, a scribing process and a cleaving process for cutting an annular glass base plate from a plate-shaped glass base plate will be described.
The scribing process is a process of providing a circular cutting line on one main surface (scribe surface) of the glass base plate with a cutter (scriber) made of super steel alloy or containing diamond particles. In the present embodiment, a circular cutting line (inner cut line) that becomes the outline of the circular hole and a circular cutting line (outer cut line) that becomes the outer outline of the glass base plate are formed simultaneously. At this time, the outer incisor and the inner incisor are formed so as to be concentric.

  The cleaving process is a method of extending the circular cutting line formed by the scribing process in the thickness direction (depth direction) of the glass base plate and separating the outside or the inside of the circular cutting line. For example, the cutting line can be extended by the difference in thermal expansion by heating or cooling at least a part of the glass base plate. Thereafter, when the outer part or the inner part is separated from the circular cutting line of the glass base plate, for example, the outer part or the inner part may be pressed in a direction perpendicular to the main surface from the circular cutting line. An annular glass base plate can be obtained by separating and removing a portion outside the outer cut line and a portion inside the inner cut line of the glass base plate.

  FIG. 1 is an elevation view showing an example of a scribing apparatus 1 for cutting an annular glass base plate from a plate-like glass base plate 10A. As shown in FIG. 1, the scribing apparatus 1 includes a table 2, an outer cutter wheel 3 (first circular blade), an inner cutter wheel 4 (second circular blade), and the like.

  The table 2 is a support base that supports the plate-shaped glass base plate 10A. The table 2 rotates the plate-like glass base plate 10A around the rotation center A1 perpendicular to the main surface of the plate-like glass base plate 10A relative to the outer cutter wheel 3 and the inner cutter wheel. Here, the outer cutter wheel 3 and the inner cutter wheel 4 may be rotated around the rotation center A1 while the table 2 and the plate-shaped glass base plate 10A are stationary, and the outer cutter wheel 3 and the inner cutter wheel 4 may be rotated. The table 2 and the plate-shaped glass base plate 10A may be rotated around the rotation center A1 in a stationary state. Note that an unillustrated adsorption portion that adsorbs the glass base plate 10 </ b> A may be provided on the table 2. In this case, a suction portion that sucks the plate-shaped glass base plate 10 </ b> A placed on the upper surface of the table 2 is provided at the center of the table 2. In addition, an annular recess is provided on the upper surface of the table 2 so as to surround the center portion where the suction portion is provided, and a center support portion is provided in a portion surrounded by the annular recess, and the annular recess An outer peripheral support portion is provided at an outer peripheral portion surrounding the. The center support portion and the outer periphery support portion are provided so as to protrude upward with respect to the annular recess, and the plate-like glass base plate 10A is supported by the center support portion and the outer periphery support portion. The adsorption part is configured to be fixed on the table 2 by adsorbing the plate-like glass base plate 10A supported by the center support part and the outer periphery support part.

  The upper surface of the glass base plate 10 </ b> A placed on the upper part of the table 2 is a first main surface (scribe surface) on which the outer score 11 and the inner score 12 are formed, and is in contact with the table 2. The lower surface of the base plate 10A is the second main surface (non-scribe surface). Instead of placing the glass base plate 10A on the table 2, the glass base plate 10A may be supported by sandwiching the glass base plate 10A at the outer periphery.

The outer cutter wheel 3 and the inner cutter wheel 4 are disk-shaped cutters (circular blades) made of super steel alloy or made of diamond particles.
The first embodiment and the second embodiment of the scribing apparatus 1 will be described in detail.

(First embodiment)
In the first embodiment, the outer cutter wheel 3 and the inner cutter wheel 4 are configured in consideration of the following circumstances. That is, as shown in FIG. 1, when forming the cut line on the plate-shaped glass base plate 10 </ b> A, the outer cutter wheel 3 that forms the outer cut line 11 is more than the inner cutter wheel 4 that forms the inner cut line 12. The mileage is long. When the outer cutter wheel 3 and the inner cutter wheel 4 are rotated with respect to the plate-shaped glass base plate 10 </ b> A at the same angular speed, the outer cutter wheel 3 has a higher traveling speed than the inner cutter wheel 4, and the outer cutting line 11. The contact time with the outer cutter wheel 3 per unit length is shorter than the contact time with the inner cutter wheel 4 per unit length of the inner cutting line 12. In this case, if the same force is simultaneously applied to the main surface of the plate-like glass base plate 10 </ b> A on the outer cutter wheel 3 and the inner cutter wheel 4, it is easy to bite into the plate-like glass base plate 10 </ b> A of the outer cutter wheel 3. It is assumed that the outer cutter wheel 3 is more slippery because the inner cutter wheel 4 is worse than the inner cutter wheel 4. Therefore, it is presumed that the direction (angle) of the outer cutting line 11 extending inside the glass base plate 10A is likely to vary during one round around the rotation center A1.

  Further, the outer cutter wheel 3 having a larger rotation radius with respect to the glass base plate 10 </ b> A is more likely to cause a change in the direction of the force in the rotational radius direction with respect to the glass base plate 10 </ b> A than the inner cutter wheel 4. It is presumed that the variation of the direction becomes large. Then, this inventor thought that the concentricity of the outer incisor 11 and the inner incisor 12 can be improved by improving the ease of biting into the glass base plate 10A of the outer cutter wheel 3.

  FIG. 2 is a view showing in detail an example of the form of the outer cutter wheel 3 in the first embodiment, and is an enlarged view of a portion II in FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2, and FIG. 4 is a view taken along arrow IV in FIG. As shown in FIGS. 2 to 4, an outer edge of the outer cutter wheel 3 is provided with a cutting edge ridge 31 in an annular shape. A plurality of notches 32 (first notches) are provided in the cutting edge ridge 31 with a predetermined interval (first interval C1) in the circumferential direction.

  The outer cutter wheel 3 is in a state in which the cutting edge ridge 31 is pressed against the upper main surface (first main surface) of the plate-like glass base plate 10A with respect to the plate-like glass base plate 10A around the rotation center A1. And rotate relative to each other. At this time, the outer cutter wheel 3 rotates around the rotation axis A2 parallel to the rotation radius direction around the rotation center A1. The outer main cutter wheel 3 rotates around the rotation axis A2 while rotating and moving relative to the plate-like glass base plate 10A around the rotation center A1, so that the upper main surface of the plate-like glass base plate 10A is rotated. The outer incisor 11 is formed at a portion in contact with the cutting edge ridge 31. The distance from the rotation center A1 to the cutting edge ridge 31 at this time is a rotation radius (first rotation radius R1) around the rotation center A1 of the outer cutter wheel 3, and the plate-like glass element is formed by the first rotation radius R1. The radius of the outer shape of the annular glass base plate cut out from the plate 10A is determined.

  FIG. 5 is a diagram showing details of an example of the inner cutter wheel 4 in the first embodiment, and is an enlarged view of a V portion in FIG. 1. 6 is a cross-sectional view taken along the line VI-VI in FIG. 5, and FIG. 7 is a view taken along the line VII in FIG. As shown in FIGS. 5 to 7, a cutting edge ridge 41 is provided in an annular shape on the outer peripheral portion of the inner cutter wheel 4. The cutting edge ridge 41 is provided with a plurality of notches 42 (second notches) with a predetermined interval (second interval C2) in the circumferential direction.

  The inner cutter wheel 4 rotates relative to the plate-shaped glass base plate 10A around the rotation center A1 in a state where the cutting edge ridge 41 is pressed against the upper main surface of the plate-like glass base plate 10A. . At this time, the inner cutter wheel 4 rotates around the rotation axis A3 parallel to the rotation radius direction around the rotation center A1. The upper main surface of the plate-shaped glass base plate 10A is rotated by the inner cutter wheel 4 rotating about the rotation axis A3 while rotating and moving relative to the plate-shaped glass base plate 10A around the rotation center A1. The inner incisor 12 is formed at a portion in contact with the cutting edge ridge 41. The distance from the rotation center A1 to the cutting edge ridge 41 at this time is the rotation radius (second rotation radius R2) around the rotation center A1 of the inner cutter wheel 4, and the plate-like glass element is formed by the second rotation radius R2. The radius of the inner hole of the annular glass base plate cut out from the plate 10A is determined.

Next, a method of cutting an annular glass base plate from the plate-like glass base plate 10A in the first embodiment will be described.
First, the outer cutter wheel 3 and the inner cutter wheel 4 are pressed against the upper main surface of the plate-shaped glass base plate 10 </ b> A placed on the table 2. Next, the outer cutter wheel 3 and the inner cutter wheel 4 are rotated and moved relative to the plate-shaped glass base plate 10A around the rotation center A1. At this time, with the downward force applied to the outer cutter wheel 3 and the inner cutter wheel 4, the outer cutter wheel 3 and the inner cutter wheel 4 are rotated once around the rotation center A1 at the same angular velocity. During this time, the load on the outer cutter wheel 3 is preferably 50 to 100% of the load on the inner cutter wheel 4. As described above, the outer cut line 11 and the inner cut line 12 are formed on the upper main surface of the plate-shaped glass base plate 10A.

  In FIG. 1, the outer cutter wheel 3 is arranged on the same side as the inner cutter wheel 4 with respect to the rotation center A1. That is, the outer cutter wheel 3 and the inner cutter wheel 4 are arranged at the same phase position with respect to the rotation center A1. However, the present embodiment is not limited to this, and the outer cutter wheel 3 and the inner cutter wheel 4 may be arranged on the opposite side with respect to the rotation center A1. That is, you may arrange | position the outer cutter wheel 3 and the inner cutter wheel 4 in the position which the phase shifted | deviated 180 degrees.

Next, a portion outside the outer cut line 11 of the plate-like glass base plate 10A is heated. Then, due to the difference in thermal expansion, the outer scoring line 11 develops, and a split section that reaches the main surface (second main surface) opposite to the first main surface of the plate-like glass base plate 10A is formed. Is done.
Next, the outer part of the plate-shaped glass base plate 10 </ b> A outside the inner cut line 12 is heated. Then, due to the difference in thermal expansion, the inner scissors 12 develop, and a fractured surface that reaches the main surface (second main surface) opposite to the first main surface of the plate-like glass base plate 10A is formed. Is done.
Then, an annular glass base plate is obtained by removing a part outside the outer cut line 11 and a part inside the inner cut line 12 of the plate-like glass base plate 10A.

Here, in the first embodiment, the first notch 32 and the second notch 42 are formed so that the first interval C1 is smaller than the second interval C2. By being C1 <C2, the contact area of the outer cutter wheel 3 to the upper main surface of the plate-shaped glass base plate 10A becomes smaller than the contact area of the inner cutter wheel 4. For this reason, when the same magnitude | size force is applied below to the outer cutter wheel 3 and the inner cutter wheel 4, the pressure of the outer cutter wheel 3 to the upper main surface of the plate-shaped glass base plate 10A is changed to the inner cutter wheel. 4, the outer cutter wheel 3 is likely to bite (or bite) deeply from the upper main surface of the plate-like glass base plate 10 </ b> A into the glass base plate 10 </ b> A. Thereby, the slip when the cutting edge ridge 31 of the outer cutter wheel 3 pivots relative to the main surface so as to draw an arc on the main surface of the glass base plate 10A is suppressed, and the radius of the outer cutting line 11 is reduced. The movement of the outer cutter wheel 3 in the direction is suppressed. For this reason, the dispersion | variation in the angle of the outer incisor 11 can be made small. As a result, the variation in the distance from the rotation center A1 of the outer incisor 11 can be reduced, and the concentricity between the outer incisor 11 and the inner incisor 12 can be increased. C2-C1 is, for example, 5 to 75 μm.
Here, it is preferable that the 1st space | interval C1 is 5-40 micrometers. If the first distance C1 is less than 5 μm, the blade of the outer cutter wheel 3 may be easily applied. On the other hand, if it exceeds 40 μm, there is a risk that the outer cutter wheel 3 cannot be sufficiently bite when forming the outer peripheral cutting line 11. The second interval C2 is preferably 10 to 80 μm. If the second distance C2 is less than 10 μm, the blade of the inner cutter wheel 4 may be easily applied. On the other hand, if it exceeds 80 μm, the inner cutter wheel 4 may not be sufficiently bitten when forming the inner peripheral cut line 12. The difference between the first interval C1 and the second interval C2 is preferably at least 5 μm or more and preferably 10 μm or more in order to ensure sufficient biting of the outer cutter wheel 3 at the time of forming the outer peripheral cutting line 11. And more preferred. Moreover, although there is no upper limit in particular regarding the said difference, it is preferable that it is 75 micrometers or less from a viewpoint of durability of the front-end | tip of the outer cutter wheel 3. FIG.

  Here, the circumferential length L1 of the first cutout 32 is preferably longer than the circumferential length L2 of the second cutout 42. By being L1> L2, the outer cutter wheel 3 can easily bite into the glass base plate 10A from the upper main surface of the plate-like glass base plate 10A. The circumferential length L1 of the first notch 32 is, for example, 5 to 60 μm. The circumferential length L2 of the second notch 42 is, for example, 2 to 30 μm. The difference in the circumferential length between the first notch 32 and the second notch 42 is not particularly required, but is preferably 10 μm or more, and more preferably 15 μm or more. Moreover, although there is no upper limit in particular about the said difference, it is preferable that it is 50 micrometers or less from a viewpoint of forming the cut line 11 of an outer peripheral side stably especially.

The maximum depth D1 of the first notch 32 is preferably deeper than the maximum depth D2 of the second notch 42. By being D1> D2, the outer cutter wheel 3 is likely to bite deeply into the glass base plate 10A from the upper main surface of the plate-like glass base plate 10A.
The maximum depth D2 of the second notch 42 is preferably, for example, 1 to 15 μm. If the thickness is less than 1 μm, the inner cutter wheel 4 may not be sufficiently bite when the cut line 12 is formed. Moreover, when it exceeds 15 micrometers, there exists a possibility that the blade of the inner side cutter wheel 4 may become easy to apply. The difference D1-D2 in the maximum depth between the first notch 32 and the second notch 42 is not particularly required, but is preferably 1 μm or more, and more preferably 2 μm or more. The upper limit of the difference is not particularly limited, but is preferably 10 μm or less from the viewpoint of durability of the outer cutter wheel 3.

  It is preferable that the notch 32 is formed so that the circumferential length L1 of the notch 32 is longer than the first interval C1. By setting L1> C1, the contact area of the outer cutter wheel 3 with the main surface on the upper side of the plate-like glass base plate 10A becomes small, so that when a force is applied downward to the outer cutter wheel 3, the plate-like glass The pressure of the outer cutter wheel 3 on the upper main surface of the glass base plate 10A is increased, and the outer cutter wheel 3 is likely to bite deeply into the glass base plate 10A from the upper main surface of the plate-like glass base plate 10A. . L1-C1 is, for example, 10 to 40 μm.

  Moreover, it is preferable that the notch 42 is formed so that the circumferential length L2 of the notch 42 is shorter than the second interval C2. By setting L2 <C2, the contact area of the inner cutter wheel 4 to the upper main surface of the plate-like glass base plate 10A increases, so that when a force is applied downward to the inner cutter wheel 4, the plate-like glass The pressure of the inner cutter wheel 4 on the upper main surface of the glass base plate 10A is reduced, and the inner cutter wheel 4 is less likely to bite into the glass base plate 10A from the upper main surface of the plate-like glass base plate 10A. For this reason, the outer cutter wheel 3 can easily bite deeply into the glass base plate 10A from the main surface on the upper side of the plate-like glass base plate 10A. C2-L2 is, for example, 5 to 30 μm.

  FIG. 8 is a perspective view showing the annular glass base plate 10B obtained as described above. As shown in FIG. 8, the annular glass base plate 10 </ b> B has an outer peripheral end surface 13, an inner peripheral end surface 14, a first main surface 15, and a second main surface 16.

The outer peripheral end face 13 is a fractured cross section in which the outer cut line 11 of the plate-like glass base plate 10A has advanced to reach the second main surface.
The inner peripheral end surface 14 is a fractured section in which the inner cut line 12 of the plate-like glass base plate 10A has advanced to reach the second main surface.

  The 1st main surface 15 is a part of 1st main surface in which the outer cut 11 and the inner cut 12 of the plate-shaped glass base plate 10A were formed (scribe surface). The second main surface 16 is a main surface opposite to the first main surface 15 of the annular glass base plate 10B (non-scribe surface), and is in contact with the table 2 of the plate-like glass base plate 10A. 2 is a part of the main surface.

  The outer periphery 15 </ b> A of the first main surface 15 is formed by the outer cut line 11. On the other hand, the outer periphery 16A of the second main surface 16 is formed by the split section extending from the outer cut line 11 reaching the second main surface of the plate-like glass base plate 10A.

  The inner circumference 15 </ b> B of the first main surface 15 is formed by the inner cut line 12. On the other hand, the inner periphery 16B of the second main surface 16 is formed by the split section extending from the inner cut line 12 reaching the second main surface of the plate-like glass base plate 10A.

In the first embodiment, by using the outer cutter wheel 3 and the inner cutter wheel 4 described above, it is possible to reduce the variation in the direction (angle) in which the outer cut line 11 extends into the glass base plate 10A in particular, As a result, the variation in the distance from the rotation center A1 of the outer incisor 11 can be reduced, and the concentricity between the outer incisor 11 and the inner incisor 12 can be increased. The concentricity between the outer periphery and the inner periphery of the annular glass base plate 10B formed in this way is preferably 15 μm or less. Here, the concentricity is represented by the distance between the center of the outer circumference circle and the center of the inner circumference circle. The concentricity can be measured, for example, with a roundness / cylindrical shape measuring machine or the like using an ono-blade probe whose tip is wider than the plate thickness.
Moreover, while forming the outer incisor 11 using the said outer cutter wheel 3, and forming the inner incisor 12 using the inner cutter wheel 4, the outer periphery 15A and the inner periphery 15B of the 1st main surface 15 and The concentricity can be reduced. Here, the concentricity is represented by the distance between the centers of the outer periphery 15A and the inner periphery 15B.

  In addition, the roundness of the outer periphery 15A of the first main surface 15 that is a scribe surface is smaller than the roundness of the outer periphery 16A of the second main surface 16 that is a non-scribe surface. The difference between the roundness of the shape of the outer periphery 15A and the roundness of the shape of the outer periphery 16A is preferably 100 μm or less from the viewpoint of reducing the machining allowance for the end processing in the subsequent process.

  Here, the roundness refers to the magnitude of deviation from a geometrically correct circle (geometric circle) in a circular form. The roundness is expressed by the difference between the radii of two circles when the interval between the two concentric circles is minimum when the circular shape is sandwiched between two concentric geometric circles (JIS B0621). When measuring the roundness of the outer circumference 15A and the outer circumference 16A using a roundness / cylindrical shape measuring machine or the like, measurement conditions are set so that the profile of the boundary portion between one main surface and the end face can be obtained with high accuracy. Need to be optimized. For example, when using a probe with a spherical tip, the diameter of the probe tip should be sufficiently small, and when using an ono-blade probe with a tip wider than the plate thickness, adjust the angle at which the probe is applied. That's fine.

  In the process of manufacturing a glass substrate for a magnetic disk from the annular glass base plate 10B obtained by the cleaving process in this way, chamfering processing by end face grinding using a general-purpose grindstone for the outer peripheral end face 13 and the inner peripheral end face 14 is performed. Is done. As described above, since the concentricity between the outer incisor 11 and the inner incisor 12 can be increased, the outer peripheral end face 13 of the annular glass base plate 10B formed from the outer incisor 11 and the inner incisor 12 and The machining allowance in a subsequent process such as chamfering processing or end surface polishing processing for the inner peripheral end surface 14 can be reduced, the processing efficiency of the annular glass base plate can be increased, and further, the annular glass substrate, For example, the production efficiency of a glass substrate for a magnetic disk can be increased.

(Second Embodiment)
In the second embodiment, the outer cutter wheel 3 and the inner cutter wheel 4 are configured in consideration of the following circumstances. That is, the cut line formed by pressing the cutter wheels (the outer cutter wheel 3 and the inner cutter wheel 4) toward the first main surface of the glass base plate 10A is in a plane including the cutting edge of the cutter wheel. Is formed so as to extend in a direction away from the cutting edge. For this reason, when the cutter wheel rotates relative to the plate-shaped glass base plate 10A along the main surface, the cut line is formed in a line segment having a predetermined length in contact with the circular orbit of the cutter. When the cutter moves along a circular orbit, this line segment-like cut line is continued along the circular orbit to form a circular cut line. However, in the glass having a high cutting resistance, the cut lines extending inside the glass base plate 10A tend to be inclined radially inward from the direction perpendicular to the first main surface.
In particular, when the outer incisor 11 and the inner incisor 12 are simultaneously formed, the inner incisor 12 is more intricate than the outer incisor 11 as a result of a complicated influence of a difference in the radius of curvature, a difference in the traveling speed of the cutter, and the like. It is presumed that the film is likely to be inclined toward the inner side in the radial direction from the direction perpendicular to the first main surface.
On the other hand, among the two inclined surfaces forming the cutting edge of the cutter wheel, the inclined surface in the center direction of the circular track is arranged so as to be closer to the first main surface than the inclined surface outside the circular track. If the cut line is formed in the state, it is assumed that the formed cut line is formed toward the outside of the circular orbit. Therefore, the present inventor has the inner cutter wheel 4 that forms the inner cutting line 12, and the inclined surface (second inner inclined surface 44) on the center side of the inner cutting line 12 with respect to the cutting edge ridge 41 has a cutting edge ridge. When the inner scissors 12 are formed in a state of being arranged closer to the main surface of the plate-like glass base plate 10A than the inclined surface (second outer inclined surface 45) outside the inner scissors 12 than 41, glass is formed. It was inferred that the incision 12 that extends inside the base plate 10A can be reduced from being inclined inward in the radial direction. Accordingly, it was inferred that the split cross section of the inner cut bar 12 and the split cross section of the outer cut bar 11 can be grown in substantially the same direction with respect to the main surface.

FIG. 9 is a diagram illustrating details of an example of the outer cutter wheel 3 according to the second embodiment. As shown in FIG. 9, the cutting edge ridge 31 of the outer cutter wheel 3 is formed by a first inner inclined surface 34 and a first outer inclined surface 35.
The first inner inclined surface 34 is closer to the rotation center A1 side than the first plane P1 including the cutting edge ridge 31 that circulates around the outer cutter wheel 3, and the first outer inclined surface 35 is relative to the first plane P1. It is on the side opposite to the rotation center A1. Both of the first inner inclined surface 34 and the first outer inclined surface 35 have the shape of the side surface of the truncated cone so as to approach the rotation axis A2 as the distance from the cutting edge ridge 31 increases.

  The inner cutter wheel 4 is a disc-shaped cutter (circular blade) made of super steel alloy or containing diamond particles, and a cutting edge ridge 41 is provided annularly on the outer peripheral portion.

  The inner cutter wheel 4 has a predetermined radius (second rotation radius R2, R2 <R1) from the rotation center A1 in a state where the cutting edge ridge 41 is pressed against the first main surface of the plate-shaped glass base plate 10A. It rotates relative to the plate-shaped glass base plate 10A along a circular orbit (second circular orbit). At this time, the inner cutter wheel 4 rotates around the rotation axis A3 parallel to the direction of the second rotation radius R2. The inner cutter wheel 4 rotates about the rotation axis A3 while rotating and moving relative to the plate-like glass base plate 10A along the second circular orbit. The inner incisor 12 is formed at a portion of the main surface 1 that is in contact with the cutting edge ridge 41. The radius of the inner cut line 12 is R2, and the radius of the inner peripheral end surface of the annular glass base plate cut out from the plate-like glass base plate 10A is determined by the second rotation radius R2.

FIG. 10 is an enlarged view showing an example of the form of the inner cutter wheel 4 shown in FIG. 1 in the second embodiment. As shown in FIG. 10, the cutting edge ridge 41 of the inner cutter wheel 4 is formed by a second inner inclined surface 44 and a second outer inclined surface 45.
The second inner inclined surface 44 is on the rotation center A1 side with respect to the second plane P2 including the cutting edge ridge 41 that circulates the inner cutter wheel 4, and the second outer inclined surface 45 is with respect to the second plane P2. It is on the side opposite to the rotation center A1. Each of the second inner inclined surface 44 and the second outer inclined surface 45 has the shape of a side surface of a truncated cone that approaches the rotation axis A3 as it moves away from the cutting edge ridge 41.

  In general, the inner scissors 12 having a trajectory having a smaller radius than the trajectory of the outer scissors 11 tend to be formed so as to incline inward in the radial direction from the main surface of the plate-like glass base plate 10A. There is. The cause is considered as follows.

  When the cutter moves along the circular orbit, the orientation of the plane including the cutting edge ridge will continue to change in the center direction of the circular orbit, so the center side of the circular orbit at the part that bites into the main surface of the cutting edge A force in the center direction of the circular orbit acts on the main surface of the glass base plate from the inclined surface. This force increases as the radius of the circular orbit decreases.

For this reason, the force acting on the first main surface of the plate-like glass base plate 10A from the second inner inclined surface 44 of the inner cutter wheel 4 moving along the second circular orbit in the direction of the rotation center A1. The component force of the plate-shaped glass base plate 10A is from the first inner inclined surface 34 of the outer cutter wheel 3 that moves along the first circular orbit having a smaller curvature than the second circular orbit (having a larger radius of curvature). The force acting on the first main surface is larger than the component force in the direction of the rotation center A1.
Therefore, the inner incisor 12 tends to be formed more inclined than the outer incisor 11 toward the rotation center A1 side of the second circular orbit. That is, as shown in FIG. 9, the angle formed by the outer incisor 11 and a straight line extending from the outer incisor 11 toward the center of the first main surface is θ _11, and as shown in FIG. If the angle formed by the straight line from the inner cut line 12 toward the center of the first main surface is θ ₁₂ , θ ₁₂ tends to be smaller than θ ₁₁ .

On the other hand, in the second embodiment, the angle between the first inner inclined surface 34 and the first plane P1 is θi1, the angle between the first outer inclined surface 35 and the first plane P1 is θo1, and the second inner inclination. When the angle between the surface 44 and the second plane P2 is θi2, the angle between the second outer inclined surface 45 and the second plane P2 is θo2, and θi1−θo1 = Δθ1 and θi2−θo2 = Δθ2 are defined, Δθ1 <An angle θ _P1 between the outer cutter wheel 3 (first circular blade) and the inner cutter wheel 4 (second circular blade) satisfying the relationship of Δθ2 with the first main surface of the first plane _P1 is the second plane. The first main surface is brought into contact with the first main surface so as to be equal to the angle θ _P2 formed with the first main surface of _P2 . Thereby, the inner scoring line 12 extending inside the glass base plate 10A can be more easily directed from the center to the outer peripheral side of the glass base plate 10A than the direction in which the outer scissor 11 extends inside the glass base plate 10A. It is possible to reduce a tendency that the split section of the inner cut line 12 is formed so as to be inclined inward in the radial direction from the main surface of the plate-shaped glass base plate 10A toward the inside. Note that θi1, θo1, θi2, and θo2 are each preferably in the range of 40 to 80 °. If it is less than 40 °, the cutter wheel life (number of treatments) may be shortened, and if it is greater than 80 °, the cut line may not be formed well. Δθ2−Δθ1 is, for example, not less than 5 ° and not more than 30 °.

  Here, it is preferable that θi2> θo2. When the inner cutter wheel 4 is moved along the second circular orbit while the inner cutter wheel 4 is arranged so as to satisfy θi2> θo2, the first of the plate-shaped glass base plate 10A is moved from the second inner inclined surface 44. The component of the force acting on the main surface in the direction of the rotation center A1 is the component of the force acting on the first main surface of the plate-like glass base plate 10A from the second outer inclined surface 45 in the outer direction. Power is greater. For this reason, by making θi2> θo2, it is possible to make a tendency that the split cross section of the inner incisor 12 is inclined and formed toward the outside of the second circular orbit. Accordingly, it is possible to reduce the tendency that the split cross section of the inner cutting line 12 is inclined toward the radially inner side due to the small radius of the second circular orbit. The difference between θi2 and θo2 is preferably 30 ° or less. If it is larger than 30 °, the split cross section of the inner incisor 12 is excessively inclined outward in the radial direction. θi2−θo2 is, for example, not less than 5 ° and not more than 30 °.

  On the other hand, in the outer incisor 11 having a radius larger than that of the inner incisor 12, the tendency to be inclined toward the inner side in the radial direction from the main surface of the plate-shaped glass base plate 10A is smaller than that in the inner incisor 12. Therefore, by setting θi1 <θi2, the angles of the outer cut 11 and the inner cut 12 extending to the inside of the glass base plate 10A with respect to the main surface of the plate-like glass base plate 10A can be made substantially the same. Thereby, when the outer cut line 11 and the inner cut line 12 are grown and the plate-shaped glass base plate 10A is cut, the split cross section of the outer cut line 11 that becomes the outer peripheral end surface of the obtained annular glass base plate and It is possible to form the split cross section of the inner cutting line 12 serving as the inner peripheral end face at substantially the same angle with respect to the main surface. Here, “substantially the same angle” means that the difference in angle is less than 10 °. Therefore, the machining allowance for grinding the outer peripheral end face 13 and the inner peripheral end face 14 of the annular glass base plate 10B to obtain the annular glass substrate can be reduced, and the processing efficiency can be increased. . Further, by satisfying θi1 <θi2, the cutting resistance when forming the inner incisor 12 can be reduced, and chipping defects around the inner incisor 12 can be reduced. Further, θi2−θi1 is, for example, not less than 5 ° and not more than 30 °.

  The angle (θi1 + θo1) formed by the first inner inclined surface 34 and the first outer inclined surface 35 is preferably smaller than the angle (θi2 + θo2) formed by the second inner inclined surface 44 and the second outer inclined surface 45. By setting (θi1 + θo1) <(θi2 + θo2), it is possible to reduce cutting resistance when forming the inner incisor 12, and to reduce chipping defects around the inner incisor 12. The angles (θi1 + θo1) and (θi2 + θo2) are preferably adjusted within a range of 100 to 140 °, respectively. If the angle is less than 100 °, the cutter wheel life (number of treatments) may be shortened, and if it is greater than 140 °, the cut line may not be formed well. (Θi2 + θo2) − (θi1 + θo1) is, for example, not less than 5 ° and not more than + 30 °.

  It is preferable that the angle formed between the first inner inclined surface 34 and the main surface is equal to the angle formed between the first outer inclined surface 35 and the main surface. That is, when the angle between the first inner inclined surface 34 and the first plane P1 is θi1, and the angle between the first outer inclined surface 35 and the first plane P1 is θo1, it is preferable that θi1 = θo1. By carrying out like this, since the outer incision 11 can be formed substantially perpendicularly with respect to the glass surface, the allowance on the outer peripheral side can be reduced in, for example, a chamfering process in a subsequent process.

  As described above, the smaller the radius of the circular orbit that is the locus of the cut line, the more likely the cut surface of the cut line is formed to be inclined inward in the radial direction. For this reason, it is preferable to apply 2nd Embodiment to manufacture of the glass substrate for magnetic discs with a small internal hole radius, and another annular | circular shaped glass base plate. Specifically, it is preferable to apply the second embodiment when the radius of the second circular orbit is 20 mm or less. According to the study of the present inventors, when the radius of the circular orbit is 20 mm or less, the tendency that the split section of the cut line is inclined and formed inward in the radial direction becomes remarkable.

  When the cutter is rotationally moved along the circular orbit with respect to the first main surface of the plate-shaped glass base plate having a small linear expansion coefficient, the tendency of the radial inclination to be increased as the circular orbit is smaller.

For this reason, when processing the plate-shaped glass base plate which consists of glass with a small linear expansion coefficient, it is preferable to apply 2nd Embodiment. Specifically, it is preferably applied to shape processing of a plate-shaped glass base plate having a linear expansion coefficient of 65 × 10 ⁻⁷ / ° C. or less. In particular, it is more preferable to apply to shape processing of a glass base plate having a linear expansion coefficient of 50 × 10 ⁻⁷ / ° C. or less. When applied to the shape processing of a plate-like glass base plate 10A having a linear expansion coefficient of 50 × 10 ⁻⁷ / ° C. or less, the inner portion of the glass base plate 10B than the inner cut line 12 can be easily removed (removed). Can do. In addition, a linear expansion coefficient here is an average thermal expansion coefficient in 50-350 degreeC.

Next, a method for cutting an annular glass base plate from the plate-like glass base plate 10A will be described.
First, the outer cutter wheel 3 and the inner cutter wheel 4 are pressed against the upper main surface of the plate-shaped glass base plate 10 </ b> A placed on the table 2. At this time, the outer cutter wheel 3 and the inner cutter wheel 4 are set such that the angle θ _P1 formed with the upper main surface of the first plane P1 is substantially the same as the angle θ _P2 formed with the upper main surface of the second plane P2. Is brought into contact with the upper main surface. Here, the “substantially the same” angle means that the angle difference is within 3 °.

  At this time, in order to make the outer cut line 11 formed by the outer cutter wheel 3 perpendicular to the upper main surface (first main surface), the outer cutter wheel so that the first plane P1 is perpendicular to the upper main surface. 3 is preferably brought into contact with the upper main surface. Further, in order to make the inner cutting line 12 formed by the inner cutter wheel 4 perpendicular to the upper main surface, the inner cutter wheel 4 is brought into contact with the upper main surface so that the second plane P2 is perpendicular to the upper main surface. It is preferable. Here, “perpendicular to the upper main surface” means that the angle formed with the normal line of the upper main surface is 5 ° or less. By pressing the cutter wheel perpendicularly to the main surface in this way, the load from the cutter wheel to the glass is easily transmitted efficiently, and chipping is less likely to occur around the cut line. It is possible to prevent the cutting edge from being broken.

  Next, the outer cutter wheel 3 and the inner cutter wheel 4 are rotated and moved relative to the plate-shaped glass base plate 10A around the rotation center A1. At this time, the outer cutter wheel 3 and the inner cutter wheel 4 are rotated about the rotation center A1 at the same angular velocity with the force of approximately the same magnitude applied to the outer cutter wheel 3 and the inner cutter wheel 4 downward. Rotate. As described above, the outer cut line 11 and the inner cut line 12 are formed on the upper main surface of the plate-shaped glass base plate 10A.

  In FIG. 1, the outer cutter wheel 3 and the inner cutter wheel 4 are disposed on the same side with respect to the rotation center A1. However, the present embodiment is not limited thereto, and the outer cutter wheel 3 may be disposed on the opposite side of the inner cutter wheel 4 with respect to the rotation center A1.

Next, a portion outside the outer cut line 11 of the plate-like glass base plate 10A is heated. Then, due to the difference in thermal expansion, the outer scoring line 11 develops, and a split section that reaches the main surface (second main surface) opposite to the first main surface of the plate-like glass base plate 10A is formed. Is done.
Next, the outer part of the plate-shaped glass base plate 10 </ b> A outside the inner cut line 12 is heated. Then, due to the difference in thermal expansion, the inner scissors 12 develop, and a fractured surface that reaches the main surface (second main surface) opposite to the first main surface of the plate-like glass base plate 10A is formed. Is done.
Thereafter, by removing a portion outside the outer cut line 11 and a portion inside the inner cut line 12 of the plate-like glass base plate 10A, an annular glass base plate 10B as shown in FIG. Is obtained. In addition, when removing the part inside the incisor 12, it is preferable that the portion is pulled downward so that the main surface is not touched and scratched.

  FIG. 11 is a diagram illustrating an example of a cross section of an annular glass base plate 10B. As shown in FIG. 11, the annular glass base plate 10 </ b> B has an outer peripheral end surface 13, an inner peripheral end surface 14, a first main surface 15, and a second main surface 16.

The outer peripheral end surface 13 is a fractured cross section in which the outer cut line 11 of the plate-like glass base plate 10 </ b> A has advanced to reach the second main surface 16.
The inner peripheral end surface 14 is a split section in which the inner cut line 12 of the plate-shaped glass base plate 10 </ b> A has advanced to reach the second main surface 16.

  The 1st main surface 15 is a part of 1st main surface in which the outer cut 11 and the inner cut 12 of the plate-shaped glass base plate 10A were formed. The second main surface 16 is a main surface opposite to the first main surface 15 of the annular glass base plate 10B, and is a second main surface that is in contact with the table 2 of the plate-like glass base plate 10A. It is a part.

The outer periphery 15 </ b> A of the first main surface 15 is formed by the outer cut line 11.
On the other hand, the outer periphery 16A of the second main surface 16 is formed by the split section extending from the outer cut line 11 reaching the second main surface 16 of the plate-like glass base plate 10A.

The inner circumference 15 </ b> B of the first main surface 15 is formed by the inner cut line 12.
On the other hand, the inner periphery 16B of the second main surface is formed by the split section extending from the inner cut line 12 reaching the second main surface of the plate-like glass base plate 10A.

In the second embodiment, the outer cut line 11 and the inner cut line 12 are grown by reducing the tendency that the split section of the inner cut line 12 is inclined toward the center side of the glass base plate 10A. When the plate-shaped glass base plate is cut, an angle θ ₁₃ formed by the outer peripheral end surface 13 that is a cut section of the outer cut bar 11 and the first main surface 15 and an inner peripheral end face that is a cut section of the inner cut bar 12. 14 and may be formed at substantially the same angle and angle theta ₁₄ of the first main surface 15. Therefore, the machining allowance for grinding the outer peripheral end face 13 and the inner peripheral end face 14 of the annular glass base plate 10B to obtain the annular glass substrate can be reduced, and the processing efficiency can be increased. . As a result, the production efficiency of the glass substrate can be increased.
Here, θ ₁₃ is an angle formed by a straight line from the outer periphery 15A toward the center of the main surface 15 and an extension line of the outer peripheral end surface 13 in the cross section including the center line of the glass base plate 10B shown in FIG. Θ ₁₄ is an angle formed by a straight line extending from the inner periphery 15B toward the center of the first main surface 15 and an extension line of the inner peripheral end surface 14 in a cross section including the center line of the glass base plate 10B. Note that “substantially the same angle” means that the difference in angle between θ ₁₃ and θ ₁₄ is less than 10 °.

In addition, in FIG. 11, although both the outer peripheral end surface 13 and the inner peripheral end surface 14 have shown the state inclined so that it might go to radial direction outward toward the 2nd main surface from the 1st main surface 15, If θ ₁₃ and θ ₁₄ are substantially the same angle, either of the outer peripheral end surface 13 and the inner peripheral end surface 14 may be perpendicular to the first main surface 15, or any of the outer peripheral end surface 13 and the inner peripheral end surface 14. Alternatively, the first main surface 15 may be inclined toward the second main surface 16 inward in the radial direction. However, it is more preferable that both the outer peripheral end face 13 and the inner peripheral end face 14 are perpendicular to the first main surface 15 because the process can be completed with the smallest machining allowance in the subsequent chamfering process.

In the annular glass base plate 10 </ b> B manufactured according to the second embodiment, the inner peripheral end surface 14 and the outer peripheral end surface 13 each include a split cross-section, and in cross-sectional view, with respect to the main surfaces of the inner peripheral end surface 14 and the outer peripheral end surface 13. It is a glass base plate whose angle difference is 10 ° or less. Since the angle difference is 10 ° or less, the processing efficiency in the chamfering processing of the annular glass base plate 10B can be increased, and the production efficiency of the annular glass substrate is increased. Note that the fractured surface can be specified by observing smooth irregularities on the surface when visually observed using a microscope having a magnification of about 10 times.
In the process of manufacturing the magnetic disk glass substrate from the annular glass base plate 10B, the outer peripheral end surface 13 and the inner peripheral end surface 14 are subjected to chamfering processing and end surface polishing processing for mirror finishing by brush polishing.

(Glass substrate manufacturing method)
Next, a method of manufacturing a magnetic disk glass substrate from the annular glass base plate obtained in the first embodiment and the second embodiment will be described. First, chamfering is performed on an annular glass base plate by end surface grinding using a general-purpose grindstone (chamfering processing). Thereby, a ring-shaped (annular) glass substrate having a chamfered surface is generated. Next, main surface grinding processing is performed (grinding processing), and end surface polishing is performed on the flattened glass substrate (end surface polishing processing). Next, 1st grinding | polishing is performed to the main surface of a glass substrate (1st grinding | polishing process). Next, second polishing is performed on the first polished glass substrate (second polishing process). In addition, you may perform the chemical strengthening process with respect to a glass substrate as needed. The glass substrate for magnetic disks is obtained through the above processing.

  According to 1st Embodiment of the manufacturing method of said glass substrate, when forming the annular | circular shaped glass base plate 10B, the roundness of the outer cut 11 is improved, the inner cut 12 and the outer The concentricity with the incisor 11 is increased. For this reason, the allowance in the chamfering process with respect to the outer peripheral end surface 13 and the inner peripheral end surface 14 can be made small, and the production efficiency of a glass substrate can be improved.

Further, according to the second embodiment, the angle between the outer cutter wheel 3 and the inner cutter wheel 4 satisfying the relationship of Δθ2> 0 and Δθ1 <Δθ2 with the main surface of the first plane P1 is the second plane P2. By contacting the main surface of a plate-shaped glass base plate (for example, a glass base plate of a glass material having a linear expansion coefficient of 65 × 10 ⁻⁷ / ° C. or less) 10A so as to be equal to the angle formed with the main surface. The difference between the machining allowance of the chamfering process at the split section of the outer cut bar 11 and the chamfering process of the chamfered process at the split section of the inner cut bar 12 of the obtained annular glass base plate 10B is reduced, and the machining allowance at the chamfering process is reduced. The amount balance is improved. For this reason, since grinding scratches and chipping can be reduced at the end portion after the chamfering process, the machining allowance in the end surface polishing process in which mirror finishing is performed by polishing the outer peripheral end face 13 and the inner peripheral end face 14 can be reduced. Can increase productivity.
Furthermore, by using the outer cutter wheel 3 and the inner cutter wheel 4 that satisfy the relationship of Δθ2> 0 and Δθ1 <Δθ2, the lifespan of the outer cutter wheel 3 and the inner cutter wheel 4 can be made equal, and the outer cutter wheel can be made equivalent. 3 and the inner cutter wheel 4 can be easily replaced at the same time, which increases the production efficiency of the glass substrate.

  Among the present embodiments, the outer cutter wheel 3 and the inner cutter wheel 4 in the first embodiment satisfy the contents of the second embodiment, that is, Δθ2> 0 and Δθ1 <Δθ2, and The scribing which cuts out the annular | circular shaped glass base plate 10B by arrange | positioning the outer cutter wheel 3 and the inner cutter wheel 4 so that the angle formed with the main surface of 1 plane P1 may become the same as the angle formed with the main surface of 2nd plane P2. It is also preferable to perform processing and cleaving processing. In addition, when the outer periphery cutting line 11 and the inner periphery cutting line 12 are formed perpendicularly with respect to the 1st type | mold surface 16, it is especially preferable since a machining allowance can be reduced most in a post process.

[Experimental Example 1]
By using the outer cutter wheel 3 and the inner cutter wheel 4 to form an outer cut 11 and an inner cut 12 on a plate-shaped glass base plate 10A having a thickness of 1 mm and cleaving, the outer diameter is about 66 mm and the inner diameter is about 66 mm. Produced an annular glass base plate 10B of about 19 mm. Circumferential distance C1 of the notch provided in the cutting edge ridge 31 of the outer cutter wheel 3, circumferential length L1, depth D1, and circumference of the notch provided in the cutting edge ridge 41 of the inner cutter wheel 4 The magnitude relationship among the direction interval C2, the circumferential length L2, and the depth D2 is as shown in Tables 1 to 3.

[Measurement of concentricity]
The shape of the outer peripheral end face and the inner peripheral end face of the obtained annular glass base plate is measured with a roundness / cylindrical shape measuring machine, and the concentricity and the roundness between the outer peripheral end face 13 and the inner peripheral end face 14 are evaluated. did. If the concentricity is 15 μm or less, the machining allowance during the chamfering with the general-purpose grindstone can be made smaller than before, which is preferable because the production efficiency of the glass substrate can be improved and the production cost can be lowered.
The results are shown in Tables 1 to 3.

  As shown in Table 1, when only the circumferential interval C1 of the notch provided in the cutting edge ridge 31 of the outer cutter wheel 3 was changed, in Examples 1 to 3 where C1 <C2, C1 = C2. The degree of concentricity could be made smaller than that of Comparative Example 1 and Comparative Example 2 where C1> C2.

  As shown in Table 2, when only the circumferential length L1 of the cutout provided on the cutting edge ridge 31 of the outer cutter wheel 3 was changed, L1 in Examples 2, 5, and 6 where L1 ≧ L2 The concentricity could be made smaller than in Example 4 where <L2. In Examples 5 and 6 where L1> L2, the concentricity could be made smaller than in Example 2 where L1 = L2.

  As shown in Table 3, when only the depth D1 of the notch provided on the cutting edge ridge 31 of the outer cutter wheel 3 was changed, in Examples 2, 8, and 9 where D1 ≧ D2, D1 <D2 The concentricity could be made smaller than in Example 7. In Examples 8 and 9 in which D1> D2, the concentricity could be made smaller than in Example 2 in which D1 = D2.

  Table 4 below shows the difference between the roundness of the outer periphery 15A of the first main surface 15 and the roundness of the outer periphery 16A of the second main surface 16. The difference in roundness between Examples 1 to 3 and Example 6 was 100 μm or less. In contrast, the difference in roundness of Comparative Example 1 exceeded 100 μm. Further, in all of Examples 4, 5, and 7 to 9, the difference in roundness was 100 μm or less.

[Experimental example 2]
As a material of the plate-like glass base plate 10A, a plate-like glass base plate (reference example) having a linear expansion coefficient of 90 to 100 (× 10 ⁻⁷ / ° C.), and a linear expansion coefficient of 55 to 65 (× 10 ⁻⁷ / ° C.) plate-like glass base plate (Comparative Examples 1, 3-5, Examples 1-3, 7-16), a linear expansion coefficient of 35 to 45 (× 10 ⁻⁷ / ° C.) and a thickness of 1 mm A plate-shaped glass base plate (Comparative Example 2, Example 4-6) was used. The outer cutting wheel 11 and the inner cutting line 12 are formed on the plate-shaped glass base plate 10A using the outer cutter wheel 3 and the inner cutter wheel 4 and cleaved, whereby the outer diameter is about 66 mm and the inner diameter is about 19 mm. An annular glass base plate 10B was prepared. At this time, the first plane including the cutting edge ridge 31 of the outer cutter wheel 3 and the second plane including the cutting edge ridge 41 of the inner cutter wheel 4 are both perpendicular to the main surface of the plate-shaped glass base plate 10A. The outer cutter wheel 3 and the inner cutter wheel 4 were brought into contact with the main surface of the plate-shaped glass base plate 10A so as to be perpendicular to the rotational radius direction.

Glass having a linear expansion coefficient of 90 to 100 (× 10 ⁻⁷ / ° C.) is glass A having the following composition, and glass having a linear expansion coefficient of 55 to 65 (× 10 ⁻⁷ / ° C.) is the following glass B and wire. An expansion coefficient of 35 to 45 (× 10 ⁻⁷ / ° C.) was prepared by appropriately adjusting from the range of the following glass C.
(Glass A)
_{SiO 2: 63~70mol%, Al 2} O 3: 4~11mol%, Li 2 O: 5~11mol%, Na 2 O: 6~14mol%, K 2 O: 0~2mol%, TiO 2: 0~ 5 mol%, ZrO2: 0 to 2.5 mol%, RO: _{2 to} 15 mol% (RO = MgO + CaO + SrO + BaO), MgO: 0-6 mol%, CaO: 1-9 mol%, SrO: 0-3 mol%, BaO: Aluminosilicate glass of 0 to ₂ mol%, other: 0 to ₃ mol%, (SiO2-Al2O3): 56.5 mol% or more.

(Glass B)
It contains SiO ₂ 40 to 61, Al ₂ O ₃ 15 to 23.5, MgO 2 to 20, CaO 0.1 to 40 in terms of mass% based on oxide, and [SiO ₂ ] + 0.43 × [Al ₂ O ₃ ] + 0.59 × [CaO] −74.6 ≦ 0 and [SiO ₂ ] + 0.21 × [MgO] + 1.16 × [CaO] −83.0 ≦ 0 Silicate glass.

(Glass C)
The Young's modulus is 87 GPa or more, the strain point is 680 ° C. or more, the average thermal expansion coefficient at 50 to 350 ° C. is 30 × 10 ^{−7 to} 47 × 10 ⁻⁷ / ° C., and the mass based on oxide %, SiO ₂ 55-69, Al ₂ O ₃ 17-27, B ₂ O ₃ 0-3, MgO 0-20, CaO 2-20, SrO 0-2, BaO 0-2, SnO ₂ 0. 01 to 1, SiO ₂ + Al ₂ O ₃ + MgO + CaO is 95 or more, MgO + CaO + SrO + BaO is 12 to 23, and [SiO ₂ ] × 6.7 + [Al ₂ O ₃ ] + [B ₂ O ₃ ] X 4.4-458 ≦ 0 alkali-free aluminosilicate glass.

  Θo1, θi1, θo2, θi2, Δθ1, and Δθ2 of the used outer cutter wheel 3 and inner cutter wheel 4 are as shown in Tables 5-7.

[Evaluation of yield]
For each of Reference Example, Comparative Example 1-5, and Example 1-16, 1000 plate-like glass base plates were processed. Using the outer cutter wheel 3 and the inner cutter wheel 4, the outer cut 11 and the inner cut 12 were formed on the main surface of the plate-like glass base plate 10 </ b> A, and cleaved. Thereafter, the outer peripheral end face 13 and the inner peripheral end face 14 of the annular glass base plate 10B after the cleaving treatment are ground by using a general-purpose grindstone for end face grinding, respectively, for 200 μm in terms of radius (400 μm in terms of diameter). ) And a chamfered surface and a side wall surface were formed on the outer peripheral end surface 13 and the inner peripheral end surface 14, respectively. The entire end surface (chamfered surface and side wall surface) of the annular glass substrate 10B after the end surface grinding process is confirmed visually and with a microscope, and any chipping (chips) or unground parts found is regarded as a defective product. Was calculated as a yield rate (%). In addition, if the yield is 80% or more, it is at a level that causes no practical problem.
The results are shown in Tables 5-7.

When the linear expansion coefficient was 90 to 100 (× 10 ⁻⁷ / ° C.), in the reference example using the outer cutter wheel and the inner cutter wheel at the same angle, the yield was 90% and there was no problem. However, in Comparative Example 1 having a linear expansion coefficient of 55 to 65 (× 10 ⁻⁷ / ° C.), the yield decreased to 20%. Furthermore, in Comparative Example 2 having a linear expansion coefficient of 35 to 45 (× 10 ⁻⁷ / ° C.), it is not possible to extract the region inside the inner cut line of the glass base plate, and an annular glass base plate is created. I couldn't. Therefore, the yield is set to 0%.

  Comparing Comparative Example 1 with Examples 1 to 3, and Comparative Example 2 with Examples 4 to 6, it can be seen that the yield is improved to 85% or more when Δθ2> 0 and Δθ1 <Δθ2.

  When Examples 10 to 12 and Examples 1 to 3 were compared, the value of (Δθ2−Δθ1) was the same, but there was a difference in yield. Since Examples 1 to 3 have a relationship of “θi1 + θo1 <θi2 + θo2”, it is presumed that it is advantageous in terms of cutting resistance and has a high yield.

  Based on the conditions of Example 2, θo1 and θi1 were changed. Here again, it can be seen that the yield is improved to 85% or more when Δθ2> 0 and Δθ1 <Δθ2.

  As described above, the annular glass base plate, the manufacturing method of the annular glass base plate, the manufacturing method of the annular glass substrate, and the manufacturing method of the glass substrate for magnetic disk of the present invention have been described in detail. Of course, the present invention is not limited to the above-described embodiment, and various improvements and modifications may be made without departing from the spirit of the present invention.

1 scribing device 2 table 3 outer cutter wheel (first circular blade)
4 Inner cutter wheel (second circular blade)
DESCRIPTION OF SYMBOLS 10A Plate-shaped glass base plate 10B Annular glass base plate 11 Outer cutting line 12 Inner cutting line 13 Outer peripheral end surface 14 Inner peripheral end surface 15 1st main surface 15A, 16A Outer periphery 15B, 16B Inner periphery 16 2nd main surface 21 Adsorption Portion 22 Concave portion 23 Center support portion 24 Outer peripheral support portions 31, 41 Cutting edge ridge 32 First notch 34 First inner inclined surface 35 First outer inclined surface 42 Second notch 44 Second inner inclined surface 45 Second outer inclined surface Surface A1 Center of rotation A2, A3 Rotation axis C1 First interval C2 Second interval R1 First rotation radius R2 Second rotation radius

(4)
The cutting edge ridge of the first circular blade has a first inner inclined surface closer to the rotation center than the first plane including the cutting edge ridge line of the first circular blade, and the first flat surface with respect to the first flat surface. Formed by a first outer inclined surface opposite to the rotation center;
The cutting edge ridge of the second circular blade has the second inner inclined surface closer to the rotation center than the second plane including the cutting edge ridge line of the second circular blade, and the second plane. Formed by a second outer inclined surface opposite to the rotation center;
An angle between the first inner inclined surface and the first plane is θi1,
An angle formed by the first outer inclined surface and the first plane is θo1,
An angle formed by the second inner inclined surface and the second plane is θi2,
An angle between the second outer inclined surface and the second plane is θo2,
θi1−θo1 = Δθ1,
When defined as θi2−θo2 = Δθ2,
The first circular blade and the second circular blade are:
Δθ2> 0 and Δθ1 <Δθ2
Satisfy the relationship
When forming the outer incisor and the inner incisor,
The first circular blade and the second circular blade are brought into contact with the main surface so that an angle formed with the main surface of the first plane is the same as an angle formed with the main surface of the second plane. The manufacturing method of the annular | circular shaped glass base plate as described in any one of (1)-(3).

(6)
An annular glass base plate that is an element of an annular glass substrate,
The glass base plate has an inner peripheral end face made of a circular hole in the center, and an outer peripheral end face,
The inner peripheral end surface and the outer peripheral end surface each include a split section,
A concentricity between the inner peripheral end surface and the outer peripheral end surface is a glass base plate of 15 μm or less.

(8)
Outer and inner incisors are formed on the main surface of a plate-like glass base plate made of a glass material having a linear expansion coefficient of 65 × 10 ⁻⁷ / ° C. or less, and the outer incisors and the inner incisors are connected to the plate. A method for producing an annular glass base plate including a shape processing treatment for forming an annular glass base plate from the plate-like glass base plate by proceeding in the thickness direction of the glass base plate,
The shape processing is
The first circular blade and the second circular blade brought into contact with one main surface of the plate-like glass base plate are relatively rotated around the main surface and one rotation center, whereby the first Forming a circular outer cutting line on the main surface with one circular blade, and forming a circular inner cutting line on the main surface with a smaller radius than the outer cutting line with the second circular blade. ,
The cutting edge ridge of the first circular blade has a first inner inclined surface closer to the rotation center than the first plane including the cutting edge ridge line of the first circular blade, and the first flat surface with respect to the first flat surface. Formed by a first outer inclined surface opposite to the rotation center;
The cutting edge ridge of the second circular blade has the second inner inclined surface closer to the rotation center than the second plane including the cutting edge ridge line of the second circular blade, and the second plane. Formed by a second outer inclined surface opposite to the rotation center;
An angle between the first inner inclined surface and the first plane is θi1,
An angle formed by the first outer inclined surface and the first plane is θo1,
An angle formed by the second inner inclined surface and the second plane is θi2,
An angle between the second outer inclined surface and the second plane is θo2,
θi1−θo1 = Δθ1,
When defined as θi2−θo2 = Δθ2,
The first circular blade and the second circular blade are:
Δθ2> 0 and Δθ1 <Δθ2
Satisfy the relationship
The first circular blade and the second circular blade are brought into contact with the main surface so that an angle formed with the main surface of the first plane is the same as an angle formed with the main surface of the second plane. A method for producing an annular glass base plate characterized by the above.

Claims (15)

The plate-like glass is formed by forming outer and inner incisors on the surface of the plate-like glass base plate, and causing the outer and inner incisors to advance in the thickness direction of the plate-like glass base plate. An annular glass base plate manufacturing method for forming an annular glass base plate from a base plate,
While pressing the first circular blade against the main surface of the plate-shaped glass base plate, the first circular blade and the plate-shaped glass base plate with a first turning radius along the main surface While forming the outer incisor by rotating relatively,
A second rotation radius that is smaller than the first rotation radius along the main surface while pressing the second circular blade against the main surface of the plate-like glass base plate. And forming the inner cut line by rotating relative to the plate-like glass base plate,
On the cutting edge of the first circular blade, a plurality of first cutouts are provided at a first interval in the circumferential direction,
A plurality of second cutouts are provided on the cutting edge of the second circular blade at a second interval in the circumferential direction,
The method for producing an annular glass base plate, wherein the first interval is smaller than the second interval.   2. The method for manufacturing an annular glass base plate according to claim 1, wherein a circumferential length of the first cutout is longer than a circumferential length of the second cutout.   The manufacturing method of the annular | circular shaped glass base plate of Claim 1 or 2 with which the length of the circumferential direction of a said 1st notch is longer than a said 1st space | interval. The cutting edge ridge of the first circular blade has a first inner inclined surface closer to the rotation center than the first plane including the cutting edge ridge line of the first circular blade, and the first flat surface with respect to the first flat surface. Formed by a first outer inclined surface opposite to the rotation center;
The cutting edge ridge of the second circular blade has the second inner inclined surface closer to the rotation center than the second plane including the cutting edge ridge line of the second circular blade, and the second plane. Formed by a second outer inclined surface opposite to the rotation center;
An angle between the first inner inclined surface and the first plane is θi1,
An angle formed by the first outer inclined surface and the first plane is θo1,
An angle formed by the second inner inclined surface and the second plane is θi2,
An angle between the second outer inclined surface and the second plane is θo2,
θi1−θo1 = Δθ1,
When defined as θi2−θo2 = Δθ2,
The first circular blade and the second circular blade are:
Δθ2> 0 and Δθ1 <Δθ2
Satisfy the relationship
When forming the outer incisor and the inner incisor,
The first circular blade and the second circular handle are brought into contact with the main surface so that an angle formed with the main surface of the first plane is the same as an angle formed with the main surface of the second plane. The manufacturing method of the annular | circular shaped glass base plate of any one of Claims 1-3 made to make.   5. A magnetic disk comprising: processing to shape an end face of the annular glass base plate manufactured by the method for manufacturing an annular glass base plate according to claim 1. Method for manufacturing glass substrate. An annular glass base plate that is an element of an annular glass substrate,
The glass base plate has an inner peripheral end face made of a circular hole in the center, and an outer peripheral end face,
A concentricity between the inner peripheral end surface and the outer peripheral end surface is a glass base plate of 15 μm or less. An annular glass base plate that is an element of an annular glass substrate,
A first main surface and a second main surface opposite to the first main surface;
The glass base plate, wherein a difference between the roundness of the outer peripheral shape of the first main surface and the roundness of the outer peripheral shape of the second main surface is 100 μm or less. Outer and inner incisors are formed on the main surface of a plate-like glass base plate made of a glass material having a linear expansion coefficient of 65 × 10 ⁻⁷ / ° C. or less, and the outer incisors and the inner incisors are connected to the plate. A method for producing an annular glass base plate including a shape processing treatment for forming an annular glass base plate from the plate-like glass base plate by proceeding in the thickness direction of the glass base plate,
The shape processing is
The first circular blade and the second circular blade brought into contact with one main surface of the plate-like glass base plate are relatively rotated around the main surface and one rotation center, whereby the first Forming a circular outer cutting line on the main surface with one circular blade, and forming a circular inner cutting line on the main surface with a smaller radius than the outer cutting line with the second circular blade. ,
The cutting edge ridge of the first circular blade has a first inner inclined surface closer to the rotation center than the first plane including the cutting edge ridge line of the first circular blade, and the first flat surface with respect to the first flat surface. Formed by a first outer inclined surface opposite to the rotation center;
The cutting edge ridge of the second circular blade has the second inner inclined surface closer to the rotation center than the second plane including the cutting edge ridge line of the second circular blade, and the second plane. Formed by a second outer inclined surface opposite to the rotation center;
An angle between the first inner inclined surface and the first plane is θi1,
An angle formed by the first outer inclined surface and the first plane is θo1,
An angle formed by the second inner inclined surface and the second plane is θi2,
An angle between the second outer inclined surface and the second plane is θo2,
θi1−θo1 = Δθ1,
When defined as θi2−θo2 = Δθ2,
The first circular blade and the second circular handle are:
Δθ2> 0 and Δθ1 <Δθ2
Satisfy the relationship
The first circular blade and the second circular handle are brought into contact with the main surface so that an angle formed with the main surface of the first plane is the same as an angle formed with the main surface of the second plane. A method for producing an annular glass base plate characterized by comprising:   The manufacturing method of the annular | circular shaped glass base plate of Claim 8 which is (theta) i1 <(theta) i2.   The manufacturing method of the annular | circular shaped glass base plate of Claim 8 or 9 which is (theta) i1 + (theta) o1 <(theta) i2 + (theta) o2.   The annular glass according to any one of claims 8 to 10, wherein a radius of a circular orbit for rotating the second circular blade relative to the plate-shaped glass base plate is 20 mm or less. Manufacturing method of base plate. The manufacturing method of the annular | circular shaped glass base plate as described in any one of Claims 8-11 which performs the shape processing of a plate-shaped glass base plate whose linear expansion coefficient is 50x10 < ^-7 > / degreeC or less.   The manufacturing method of an annular | circular shaped glass substrate including the process which shape-processes the end surface of the annular | circular shaped glass base plate manufactured by the manufacturing method of the annular | circular shaped glass base plate as described in any one of Claims 8-12.   The method for producing a glass substrate for magnetic disk, wherein the annular glass substrate according to claim 13 is a glass substrate for magnetic disk. An annular glass base plate,
The glass base plate has an inner peripheral end face made of a circular hole in the center, and an outer peripheral end face,
The glass base plate, wherein each of the inner peripheral end surface and the outer peripheral end surface includes a split cross section, and a difference in angle with respect to a main surface of each of the inner peripheral end surface and the outer peripheral end surface is 10 ° or less in a cross-sectional view.

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