JP6307407B2 - Manufacturing method of glass substrate - Google Patents

Description

The present invention relates to a method for manufacturing a glass substrate .

  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.

In order to increase the storage capacity in the hard disk device, the magnetic recording has been increased in density. For example, the magnetic recording information area is miniaturized by using a perpendicular magnetic recording method in which the magnetization direction in the magnetic layer is perpendicular to the surface of the substrate. Thereby, the storage capacity of one disk substrate can be increased. In such a disk substrate, the surface roughness of the glass substrate for magnetic disks is made as small as possible so that the growth direction of the magnetic grains is aligned in the vertical direction, and the magnetization direction of the magnetic layer is oriented substantially perpendicular to the substrate surface. It is preferable to let it go.
Furthermore, in order to further increase the storage capacity, a magnetic head equipped with a DFH (Dynamic Flying Height) mechanism is used to significantly shorten the flying distance from the magnetic recording surface, so that the recording / reproducing element of the magnetic head and the magnetic It is also practiced to increase the accuracy of recording / reproducing information (to improve the S / N ratio) by reducing the magnetic spacing between the magnetic recording layers of the disk. Even in this case, in order to stably read and write the magnetic recording information by the magnetic head for a long period of time, it is required to make the surface unevenness of the substrate of the magnetic disk as small as possible.

  In order to reduce the surface unevenness of the magnetic disk glass substrate, the glass substrate is subjected to a polishing process. There is a method of using an abrasive containing fine abrasive grains such as cerium oxide and colloidal silica for precise polishing for making a glass substrate into a final product (see, for example, Patent Document 1).

  On the other hand, if there are minute scratches on the side wall surface perpendicular to the main surface of the glass substrate and the end surface formed by the interposition surface connecting the main surface and the side wall surface, the glass substrate may be cracked. In addition, foreign matters such as abrasive grains may enter the minute scratches, and the foreign matter may then adhere to the main surface. For this reason, in order to remove minute scratches on the end face, it is also known to perform end face polishing by brush polishing using cerium oxide abrasive grains (see, for example, Patent Document 2).

JP 2010-59310 A JP2012-203922A

  By the way, when the polishing process of the end surface of the disk-shaped glass substrate is continuously performed using cerium oxide as abrasive grains, the radius of curvature of the connection portion between the side wall surface of the glass substrate and the interposed surface gradually changes. I knew it would come. This connecting portion is a portion that comes into contact with a holder for holding the magnetic disk substrate when the magnetic layer is formed. When the radius of curvature of the connection portion changes, the contact area between the holder and the connection portion changes, and the magnetic film or the like deposited on the holder may be peeled off, and may adhere to the substrate as foreign matter.

Then, an object of this invention is to provide the manufacturing method of the glass substrate which can manufacture the glass substrate of a uniform shape.

The inventor continued to polish the disk-shaped glass substrate using a polishing slurry containing cerium oxide as abrasive grains, and analyzed the particle size distribution of the abrasive grains in the polishing slurry. It turned out that the ratio of the abrasive grain with a large particle size decreases. Further, when the radius of curvature of the connecting portion of the glass substrate obtained by the polishing process was measured, it was found that the radius of curvature was smaller as the glass substrate was polished using the polishing slurry used for the long-term polishing process. It was.
Therefore, as a result of investigation by the present inventors, it is possible to keep the radius of curvature of the connecting portion in the glass substrate after the polishing treatment within a certain range by keeping the particle size distribution of the abrasive grains in the polishing slurry within a predetermined range. all right.

A first aspect of the present invention provides a polishing brush while supplying a first polishing liquid to a side wall surface perpendicular to a main surface of a glass substrate and an interposition surface connecting the main surface and the side wall surface. It is a manufacturing method of the glass substrate which has a grinding | polishing process grind | polished using.
The first polishing liquid is
A first abrasive group of cerium oxide having a first average particle size;
A second abrasive grain group of cerium oxide having a second average particle size larger than the first average particle size,
The ratio M1 / M2 of the mass M2 of the second abrasive grain group to the mass M1 of the first abrasive grain group contained in the first polishing liquid and the first polishing liquid are used in advance. The correspondence relationship between the curvature radius of the connection portion between the side wall surface and the interposition surface when the end surface polishing treatment is performed is obtained.
The ratio M1 / M2 of the first polishing liquid is adjusted so that the curvature radius becomes a desired value, and the polishing process is performed using the first polishing liquid obtained by the adjustment.

  According to the first aspect of the present invention, the ratio M1 / M2 of the mass M2 of the second abrasive grain group to the mass M1 of the first abrasive grain group is adjusted so that the radius of curvature becomes a desired value. By performing a polishing process using this polishing liquid, the radius of curvature of the connecting portion between the side wall surface and the interposed surface can be set to a desired value.

After using the first polishing liquid for the polishing treatment, measure the radius of curvature of the connecting portion of the obtained glass substrate ,
A ratio m1 / m2 of the mass m2 of the second abrasive grain group to the mass m1 of the first abrasive grain group corresponding to the measured radius of curvature is calculated so that the ratio m1 / m2 becomes the ratio M1 / M2. Determining the additional amount of the first abrasive grain group or the additional amount of the second abrasive grain group to be added to the first polishing liquid after being used for the end face polishing treatment,
It is preferable to add the determined additional amount of the first abrasive grain group or the second abrasive grain group to the first polishing liquid.

The radius of curvature of the connecting portion of the glass substrate obtained after the polishing process is measured, and based on the ratio m1 / m2 corresponding to the measured curvature radius, the ratio M1 / M2 after addition corresponds to the desired radius of curvature. To calculate the additional amount of the first abrasive grain group or the additional amount of the second abrasive grain group to be added to the first polishing liquid after being used for the end surface polishing treatment. By adding the additional amount of the first abrasive grain group or the second abrasive grain group to the first polishing liquid, the mass ratio in the first polishing liquid after the addition becomes a desired radius of curvature. It can be adjusted to a corresponding value.

Supplying a second polishing liquid between the main surface and the polishing pad, and further comprising a main surface polishing treatment for polishing the main surface of the glass substrate;
The second polishing liquid includes a first abrasive grain group having the first average particle diameter,
It is preferable to adjust the first polishing liquid by adding abrasive grains contained in the second polishing liquid used in the main surface polishing treatment to the first polishing liquid.

  The second polishing liquid can be reused by using the abrasive grains contained in the second polishing liquid used for the main surface polishing treatment for the adjustment of the first polishing liquid.

A process of adding the second abrasive grain group to the first polishing liquid each time the end face polishing process is performed for a predetermined period,
It is preferable to adjust the addition amount of the second abrasive grain group so that the addition amount of the second abrasive grain group decreases as the number of additions of the second abrasive grain group increases.

In the first abrasive grain group, the particle diameter D50 value at the point where the cumulative relative frequency obtained by accumulating the relative frequency of the abrasive grains from the smaller particle diameter side in the volume distribution of the volume distribution becomes 50% is from 0.5 μm to 0.5 μm. 1.5 μm,
The second abrasive grain group preferably has a D50 value of 3 μm to 6 μm.

The glass substrate is preferably a magnetic disk glass substrate .

ADVANTAGE OF THE INVENTION According to this invention, the curvature radius of the connection part in the glass substrate after an end surface grinding | polishing process can be made into a desired value, and a glass substrate of a uniform shape can be manufactured.

It is sectional drawing of the board | substrate for magnetic discs of this embodiment. It is an enlarged view of the II section of FIG. The mass of the second abrasive grain group relative to the radius of curvature R of the connecting portion between the side wall surface and the interposition surface when the polishing process is performed, and the mass M1 of the first abrasive grain group contained in the polishing liquid used in the polishing process It is a figure which shows the relationship with ratio M1 / M2 of M2.

  Hereinafter, the manufacturing method of the glass substrate for magnetic disks which concerns on embodiment of this invention is demonstrated in detail. The present invention is suitable for manufacturing a glass substrate for a magnetic disk having a nominal 2.5 inch size (diameter 65 mm) and a plate thickness of 0.635 mm.

(Magnetic disk glass substrate)
First, the glass substrate for magnetic disks will be described. The glass substrate for a magnetic disk has a disc shape and a ring shape in which a circular center hole concentric with the outer periphery is cut out. 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.

  A magnetic disk glass blank (hereinafter simply referred to as a glass blank) is a circular glass plate produced by press molding, and is in a form before the center hole is cut out. As a material for the glass blank, 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.

FIG. 1 is a cross-sectional view of a substrate according to an embodiment of the present invention, and FIG. 2 is an enlarged view of a portion II in FIG.
The substrate 1 of this embodiment has a main surface 10, an outer end surface 20, and an inner end surface 30.
The outer end surface 20 includes an outer wall surface 21 perpendicular to the main surface and an intervening surface 22 connecting the main surface 10 and the outer wall surface 21. The interposed surface 22 is inclined with respect to the main surface 10 and the outer wall surface 21, and the outer wall surface 21 and the interposed surface 22 are connected by a connection portion 23 having a predetermined radius of curvature R.
Inner end surface 30 includes an inner wall surface 31 perpendicular to main surface 10 and an intervening surface 32 connecting main surface 10 and inner wall surface 31. The intervening surface 32 is inclined with respect to the main surface 10 and the inner wall surface 31, and the inner wall surface 31 and the intervening surface 32 are connected by a connecting portion 33 having a predetermined radius of curvature R.

(Method for producing glass substrate for magnetic disk)
Next, a method for manufacturing a magnetic disk glass substrate will be described. First, a glass blank as a material for a plate-shaped magnetic disk glass substrate having a pair of main surfaces is produced by press molding (press molding process). Next, a circular hole is formed in the center part of the produced glass blank, and it is set as a ring-shaped (annular) glass substrate (circular hole formation process). Next, shape processing is performed on the glass substrate in which the circular holes are formed (shape processing processing). Thereby, a glass substrate is produced | generated. Next, end-face polishing is performed on the shape-processed glass substrate (end-face polishing process). Precision grinding to improve flatness is performed on the glass substrate that has been subjected to end surface polishing (precision grinding treatment). Next, 1st grinding | polishing is performed to the main surface of a glass substrate (1st grinding | polishing process). Next, chemical strengthening is performed on the glass substrate (chemical strengthening treatment). Next, second polishing is performed on the chemically strengthened glass substrate (second polishing treatment). The glass substrate for magnetic disks is obtained through the above processing. Hereinafter, each process will be described in detail.

(A) Press molding process The front-end | tip part of a molten glass flow is cut | disconnected with a cutter, the cut molten glass lump is pinched | interposed between the press molding surfaces of a pair of metal molds, and a glass blank is formed by pressing.

(B) Circular hole formation treatment A disk-shaped glass substrate having a circular hole can be obtained by forming a circular hole in a glass blank using a drill or the like.

(C) Shape processing In the shape processing, chamfering is performed on the end of the glass substrate after the circular hole formation processing.

(D) End surface polishing process In the end surface polishing process, mirror finishing is performed on the outer end surface and the inner end surface of the glass substrate by brush polishing. Here, the end surface includes a side wall surface perpendicular to the main surface of the glass substrate, and an interposed surface that connects the main surface and the side wall surface.
In the end surface polishing treatment, a plurality of glass base plates are laminated with a spacer interposed between the main surfaces. Polishing is performed by applying a polishing brush to the outer end surface and the inner end surface of the glass substrate while rotating the laminate.
By performing the end surface polishing treatment, foreign matters such as dust attached to the end surface of the glass substrate and damage such as scratches can be removed.
During the end face polishing process, a first polishing liquid containing fine particles such as cerium oxide as free abrasive grains is supplied to the polishing brush. The first polishing liquid will be described later.

(E) Precision grinding process In the precision grinding process, grinding is performed on the main surface of the glass substrate using a double-side grinding apparatus equipped with a planetary gear mechanism. Specifically, the main surface on both sides of the glass substrate is ground while holding the outer peripheral side end face of the glass substrate generated from the glass blank in the holding hole provided in the holding member of the double-side grinding apparatus. The double-sided grinding apparatus has a pair of upper and lower surface plates (upper surface plate and lower surface plate), and a glass substrate is sandwiched between the upper surface plate and the lower surface plate. Then, by moving one or both of the upper surface plate and the lower surface plate and relatively moving the glass substrate and each surface plate, both main surfaces of the glass substrate can be ground.

(F) First Polishing Process The first polishing process is a main surface polishing process, for example, removal of scratches and distortions remaining on the main surface when grinding with fixed abrasive grains, or minute surface irregularities (microwave The purpose is to adjust the business and roughness. Specifically, the main surfaces on both sides of the glass substrate are polished while holding the outer peripheral end face of the glass substrate in the holding hole provided in the polishing carrier of the double-side polishing apparatus.

  In the first polishing process, the main surface of the glass substrate is applied while supplying a second polishing liquid to the double-side polishing apparatus using a double-side polishing apparatus having the same configuration as the double-side grinding apparatus used for the grinding process using the fixed abrasive grains. Grind. In the first polishing treatment, a second polishing liquid containing fine particles such as cerium oxide as free abrasive grains is used.

  Similar to the double-side grinding apparatus, the double-side polishing apparatus has a pair of upper and lower surface plates (upper surface plate and lower surface plate), and a glass substrate is sandwiched between the upper surface plate and the lower surface plate. An annular flat polishing pad (for example, a resin polisher) is attached to the upper surface of the lower surface plate and the bottom surface of the upper surface plate as a whole. Both main surfaces of the glass substrate are polished by moving either the upper surface plate or the lower surface plate or both of them to move the glass substrate and each surface plate relatively.

(G) Chemical strengthening process In a chemical strengthening process, a glass substrate is chemically strengthened by immersing a glass substrate in a chemical strengthening liquid. As the chemical strengthening liquid, for example, a mixed melt of potassium nitrate and sodium sulfate can be used.

(H) Second polishing (final polishing) treatment The second polishing treatment aims at mirror polishing of the main surface. Also in the second polishing, a double-side polishing apparatus having the same configuration as the double-side polishing apparatus used for the first polishing is used. Specifically, the main surface on both sides of the glass substrate is polished while holding the outer peripheral side end face of the glass substrate in a holding hole provided in the polishing carrier of the double-side polishing apparatus. The machining allowance by the second polishing is, for example, about 1 to 10 nm. The second polishing process is different from the first polishing process in that the type and particle size of the free abrasive grains are different and the hardness of the resin polisher is different. Specifically, a polishing liquid containing colloidal silica having a particle size of about 5 to 100 nm as free abrasive grains is supplied between the polishing pad of the double-side polishing apparatus and the main surface of the glass substrate, and the main surface of the glass substrate is polished. The The polished glass substrate is washed with a neutral detergent, pure water, isopropyl alcohol or the like to obtain a magnetic disk glass substrate.
By performing the second polishing treatment, the roughness (Ra) of the main surface can be set to 0.1 nm or less and the micro waveness of the main surface can be set to 0.1 nm or less. In this manner, the glass substrate subjected to the second polishing is appropriately washed and dried to become a glass substrate for a magnetic disk.

Next, the first polishing liquid used for the end face polishing process and the second polishing liquid used for the first polishing process will be described.
The first polishing liquid includes a first abrasive grain group having a first average particle diameter and a second abrasive grain group having a second average particle diameter larger than the first average particle diameter.
On the other hand, the second polishing liquid contains a first abrasive grain group having a first average particle diameter.

In the first abrasive grain group, for example, in the particle size distribution of the volume distribution, the particle diameter D50 value at which the cumulative relative frequency obtained by accumulating the relative frequency of the abrasive grains from the side where the particle diameter is small becomes 50% is 0.5 μm to 1.5 μm.
The second abrasive grain group has a D50 value of 3 μm to 6 μm, for example.

  As the first abrasive grain group and the second abrasive grain group, for example, cerium oxide abrasive grains and cerium hydroxide abrasive grains can be used. In particular, in order to improve the polishing rate, it is preferable to use cerium oxide abrasive grains.

  In this embodiment, the ratio M1 / M2 of the mass M2 of the second abrasive grain group to the mass M1 of the first abrasive grain group contained in the first polishing liquid and the first polishing liquid are used in advance. Then, a correspondence relationship between the curvature radius of the connection portion between the side wall surface and the interposition surface when the end surface polishing process is performed is obtained, and the ratio M1 / M2 of the first polishing liquid is set so that the curvature radius becomes a desired value. An end face polishing process is performed using the first polishing liquid obtained by the adjustment.

  In addition, it turns out that the curvature radius of the connection part 23 becomes large, so that the average particle diameter of the whole abrasive grain is large. That is, it is known that the radius of curvature R increases as the ratio M1 / M2 decreases. For this reason, in the present embodiment, the end surface polishing process is performed using the first polishing liquid in which the ratio M1 / M2 is adjusted so as to correspond to the desired radius of curvature R, thereby reducing the curvature radius of the connection portion. It can be set to a desired value.

  Here, the relationship between the ratio M1 / M2 and the radius of curvature R is shown in FIG. The radius of curvature when the end face polishing process is performed using only the first abrasive grain group is R1, and the radius of curvature when the end face polishing process is performed using only the second abrasive grain group is R2 (R1 <R2). Then, the radius of curvature R when the ratio M1 / M2 is changed fluctuates between R1 and R2, and as the ratio of M1 increases (M1 / M2 increases), R approaches R1 from R2. That is, the straight line R = R1 in FIG. 3 is an asymptotic line of the graph of the function of R and M1 / M2. On the other hand, when M1 / M2 = 0 (M1 = 0), R = R2.

  When the end face polishing process is continuously performed using the first polishing liquid, the ratio between the mass of the first abrasive grain group and the mass of the second abrasive grain group changes. It is conceivable that the reason for this change is that the abrasive grains having a small particle size aggregate to form an abrasive grain having a large particle size, or the abrasive grains having a large particle size are broken to become abrasive grains having a small particle size. In any case, it is considered that the amount of change in mass of the first abrasive grain group and the amount of change in mass of the second abrasive grain group have the same absolute value and different signs.

In this case, the first polishing liquid can be adjusted using the relationship between the radius of curvature R and the ratio M1 / M2 so that the radius of curvature of the connection portion after the end surface polishing process becomes a desired value.
For example, when the mass of the first abrasive grain group included in the first polishing liquid at a certain time after the end face polishing process is continuously performed is m1, and the mass of the second abrasive grain group is m2, the time is The ratio m1 / m2 can be calculated by measuring the radius of curvature r of the connecting portion of the glass substrate for magnetic disk obtained by performing the end face polishing process using the first polishing liquid. Assuming that the absolute value of the mass change amount of the second abrasive grain group and the mass change amount of the first abrasive grain group due to the continuous end face polishing process are equal and the signs are different, the initial value of m1 + m2 is If known, m1 and m2 can be obtained.

Thereafter, using the obtained m1 and m2, the first polishing liquid can be adjusted so that the radius of curvature of the connecting portion after the end face polishing treatment becomes a desired value.
For example, if the ratio corresponding to the desired radius of curvature R is M1 / M2, when adding the first abrasive grain group to the first polishing liquid, if the additional amount is Δm1,
(M1 + Δm1) / m2 = M1 / M2
Δm1 that satisfies the above can be determined.
Similarly, when adding the second abrasive grain group to the first polishing liquid, if the additional amount is Δm2,
m1 / (m2 + Δm2) = M1 / M2
Δm2 that satisfies the above can be determined.
By adding the determined additional amount of the first abrasive grain group or the second abrasive grain group to the first polishing liquid, a substrate in which the radius of curvature of the connection portion has a desired value in the subsequent end face polishing process is obtained. Can be obtained.

  Note that as the abrasive grains contained in the second polishing liquid used for the first polishing treatment, abrasive grains having the same type and the same particle size distribution as the first abrasive grain group can be used. In this case, the abrasive grains contained in the second polishing liquid used in the first polishing process may be used as the first abrasive grain group used for adjusting the first polishing liquid. Since the outer end surface and inner end surface of the glass substrate to be polished in the end surface polishing process do not require the same precision as the main surface, there is no problem even if the polishing liquid used in the main surface polishing process is reused in the end surface polishing process. . By using the second polishing liquid used in the first polishing process for the adjustment of the first polishing liquid, the second polishing liquid can be reused and the amount of polishing liquid discarded can be reduced.

  In addition, when performing the process which adds a 2nd abrasive grain group to a 1st polishing liquid, it is preferable to perform this process, whenever the polishing process using a 1st polishing liquid is performed for a predetermined period. In this case, it is preferable to add so that the addition amount of the second abrasive grain group decreases as the number of additions of the second abrasive grain group increases. When the addition of the second abrasive grain group is repeated while performing the polishing process under the condition that the mass of the abrasive grains of the second abrasive grain group gradually decreases, the grain size becomes larger than that of the first abrasive grain group. This is because the proportion of abrasive grains having a grain size smaller than that of the abrasive grain group 2 increases and the dispersion of the grain size distribution becomes large. The first polishing liquid can be suitably adjusted by reducing the addition amount of the second abrasive grain group as the number of additions of the second abrasive grain group increases.

As mentioned above, although the manufacturing method of the glass substrate of this invention was demonstrated in detail, this invention is not limited to the said embodiment and Example, Even if it is variously improved and changed in the range which does not deviate from the main point of this invention. Of course it is good.

〔Example〕
Examples of the present invention will be described below.
The free abrasive grains of cerium oxide having a D50 value of 1 μm were taken as the first free abrasive grain group. The mass to be added is M1.
A free abrasive grain of cerium oxide having a particle size distribution with a D50 value of 4 μm was taken as a second free abrasive grain group. The mass to be added is M2.
The initial mass ratio was M1: M2 = 4: 1, and a 10 wt% cerium oxide polishing liquid was prepared. Fifty (one batch) glass substrates were stacked with a spacer in between, and an edge polishing process was performed on the outer peripheral edge of the glass substrate using a polishing brush. When the radius of curvature of the connecting portion at the outer peripheral end after the first batch polishing treatment was measured, the average value of the radius of curvature was 400 μm.

While circulating the first polishing liquid, 100 batches of edge polishing of the glass substrate were performed. The glass substrate was replaced with a new one each time. When the radius of curvature of the connecting portion of the 100th batch of glass substrates was measured, the radius of curvature decreased to 200 μm. After the end face polishing process for 100 batches is completed, the correspondence between the ratio M1 / M2 of the mass M2 of the second abrasive grain group to the mass M1 of the first abrasive grain group and the curvature radius R is obtained in advance. The mass ratio (m1 / m2) between the mass (m1) of the first free abrasive grain group and the mass (m2) of the second free abrasive grain group was calculated as 2.
Next, the second abrasive grain group was appropriately added to the first polishing liquid, and the mass ratio was adjusted to 4 by stirring. One batch of end polishing of the glass substrate was performed using the adjusted first polishing liquid, and the radius of curvature of the connecting portion of the glass substrate after the treatment was measured. As a result, the radius of curvature returned to 400 μm.

  Thus, according to this embodiment, even when the particle size distribution of the abrasive grains contained in the polishing liquid is changed by continuously performing the end surface polishing process, the particle size distribution of the polishing liquid is adjusted, and after the end surface polishing process The curvature radius of the connecting portion in the glass substrate can be set to a desired value.

DESCRIPTION OF SYMBOLS 1 Glass substrate 10 Main surface 20 Outer end surface 21 Outer wall surface 22 Interposition surface 23 Connection part 30 Inner end surface 31 Inner wall surface 32 Interposition surface 33 Connection part

Claims (6)

An end surface for polishing a side wall surface perpendicular to the main surface of the glass substrate and an end surface composed of an interposition surface connecting the main surface and the side wall surface with a polishing brush while supplying a first polishing liquid. A method for producing a glass substrate having a polishing treatment,
The first polishing liquid is
A first abrasive group of cerium oxide having a first average particle size;
A second abrasive grain group of cerium oxide having a second average particle size larger than the first average particle size,
A ratio M1 / M2 of the mass M2 of the second abrasive grain group to the mass M1 of the first abrasive grain group contained in the first polishing liquid and an end face using the first polishing liquid in advance. Finding the correspondence between the curvature radius of the connecting portion between the side wall surface and the interposition surface when the polishing process is performed,
Adjusting the ratio M1 / M2 of the first polishing liquid so that the curvature radius becomes a desired value;
A method for producing a glass substrate , wherein the end surface polishing treatment is performed using the first polishing liquid obtained by the adjustment. After using the first polishing liquid for the end surface polishing treatment, measure the radius of curvature of the connection portion of the obtained glass substrate ,
The ratio m1 / m2 of the mass m2 of the second abrasive grain group to the mass m1 of the first abrasive grain group corresponding to the measured radius of curvature is calculated,
An additional amount of the first abrasive grain group or the second abrasive grain group to be added to the first polishing liquid after being used for the end surface polishing treatment so that the ratio m1 / m2 becomes the ratio M1 / M2. Determine the additional amount of
The method for producing a glass substrate according to claim 1, wherein the determined additional amount of the first abrasive grain group or the second abrasive grain group is added to the first polishing liquid. Supplying a second polishing liquid between the main surface and the polishing pad, and further comprising a main surface polishing treatment for polishing the main surface of the glass substrate;
The second polishing liquid includes a first abrasive grain group having the first average particle diameter,
The said 1st polishing liquid is adjusted by adding the abrasive grain contained in the said 2nd polishing liquid used for the said main surface polishing process to the said 1st polishing liquid, The Claim 1 or 2 Glass substrate manufacturing method. A process of adding the second abrasive grain group to the first polishing liquid each time the end face polishing process is performed for a predetermined period,
The addition amount of the second abrasive grain group is adjusted so that the addition amount of the second abrasive grain group decreases as the number of times of the process of adding the second abrasive grain group increases. The manufacturing method of the glass substrate as described in any one of -3. In the first abrasive grain group, the particle diameter D50 value at a point where the cumulative relative frequency obtained by accumulating the relative frequency of the abrasive grains from the smaller particle diameter side in the volume distribution is 50% is 0.5 μm to 1.5 μm,
The said 2nd abrasive grain group is a manufacturing method of the glass substrate as described in any one of Claims 1-4 whose D50 value is 3 micrometers-6 micrometers. The said glass substrate is a manufacturing method of the glass substrate as described in any one of Claims 1-5 which is a glass substrate for magnetic discs .

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