JP2011045950A - Working device for glass substrate, method of working glass substrate, glass substrate for magnetic disk or glass substrate for photomask manufactured by the method, and method of repeatedly working glass substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a working device for a glass substrate, reducing scratches occurring on the glass substrate by removing metallic foreign matters, and also to provide a method of working a glass substrate, a glass substrate for a magnetic disk or a glass substrate for a photomask, manufactured by the method, and a method of repeatedly working a glass substrate. <P>SOLUTION: This working device for a glass substrate works the glass substrate held between an upper surface plate and a lower surface plate while supplying slurry or coolant thereto. The working device includes a magnet covered by a peelable covering material in a circulating passage through which the slurry or coolant is circulated. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a glass substrate processing apparatus, a glass substrate processing and manufacturing method, a magnetic disk glass substrate or a photomask glass substrate manufactured by the method, and a method of repeatedly processing a glass substrate.

  In recent years, glass substrates have been used in various industrial fields beyond conventional applications. For example, glass substrates according to applications are used in various electronic devices.

  For example, a personal computer (PC) or the like is provided with a hard disk drive (HDD) or the like as an external storage device. Usually, this hard disk drive is equipped with a magnetic disk known as computer storage. This magnetic disk has a structure in which a magnetic layer or the like is formed on an appropriate substrate such as an aluminum alloy substrate.

  In recent years, a glass substrate, which is a high-strength and high-rigidity material, has been widely used as a magnetic disk substrate in place of a fragile metal substrate. Further, glass substrates have attracted attention as magnetic disk substrates for server applications.

  As a processing apparatus for manufacturing such a glass substrate, a double-sided processing apparatus having a processing unit 100 as illustrated in FIG. 5 is used. The processing unit 100 includes a carrier mounting unit having an internal gear 101 and a sun gear 102 that are driven to rotate at a predetermined rotation ratio, and a metal upper surface plate 103 that is driven to rotate in reverse with the carrier mounting unit interposed therebetween. And a lower surface plate 104. A plurality of carriers 107 that mesh with the internal gear 101 and the sun gear 102 are mounted on the carrier mounting portion. The carrier 107 rotates on its own axis and rotates in a planetary gear that revolves around the sun gear 102. By this planetary gear movement, both surfaces of the glass substrate 105 mounted on the carrier 107 are the upper surface plate 103 and the lower surface plate. It is processed at the same time by friction with 104.

  This double-sided processing machine has a lapping process for correcting the flatness at a high processing speed using large abrasive grains of 3.0 μm or more and hard upper and lower surface plates 103, 104, small abrasive grains of 2.0 μm or less, and a urethane polishing pad. It is used in a polishing process in which mirror processing is performed at a processing speed slower than the lapping process using the attached upper and lower surface plates 103 and 104.

  However, this double-sided processing apparatus has a problem in that foreign matter is mixed into the slurry or coolant and the surface of the glass substrate is damaged. This foreign matter may be wear debris on the upper and lower surface plates 103 and 104, or wear debris from the gear, metal debris generated from a device such as a pumping pump provided on the supply path of slurry or coolant.

  In particular, in the lapping process in which the glass substrate is in direct contact with a hard surface plate or a hard polishing pad, a flaw having a crack depth of 10 μm or more is likely to occur when foreign matter is mixed in, and cracks may occur during processing. In some cases, scratches could not be removed in the polishing process, and it was determined to be defective at the final inspection stage. Therefore, Patent Documents 1 and 2 propose a method of removing a foreign substance by arranging a magnet strainer in a circulation path.

JP 2006-99944 A JP 2007-207393 A

  However, in the method of disposing a magnet strainer in the circulation path described in Patent Documents 1 and 2, a large amount of metal gear wear debris and metal surface plate wear debris adhere to the magnet, and the collection efficiency decreases immediately after use. The pipes were clogged and difficult to remove. In addition, since the magnet directly touches the slurry or coolant containing water as the main dispersion medium, the magnet itself easily changes in quality and the magnetic force decreases, making continuous operation difficult.

  Therefore, in view of the circumstances described above, the present invention provides a glass substrate processing apparatus, a glass substrate processing method, and a magnetic disk glass manufactured by the method, which can reduce the occurrence of scratches on the glass substrate by removing metallic foreign objects. It is an object of the present invention to provide a method for processing a substrate or a glass substrate for a photomask and a glass substrate repeatedly.

The present invention is a glass substrate processing apparatus for processing a glass substrate held between an upper surface plate and a lower surface plate while supplying slurry or coolant, and is peeled off in a circulation path through which the slurry or the coolant circulates. There is provided a glass substrate processing apparatus comprising a magnet coated with a possible covering material.
In the processing apparatus, the coating material is preferably a resin, and the resin is polyethylene, polyvinylidene chloride, polypropylene, polyvinylidene fluoride, polyvinyl chloride, polyvinyl alcohol, polyethylene terephthalate, polytrimethylene terephthalate. It is preferably one or more resins selected from the group consisting of polybutylene terephthalate and polyacryl.
Moreover, in the said processing apparatus, it is preferable that the said magnet is a permanent magnet.
Moreover, in the said processing apparatus, it is preferable that the magnetic flux density of the said permanent magnet is 1000 gauss or more and 14000 gauss or less, Furthermore, it is preferable that it is 9000 gauss or more and 14000 gauss or less.
Moreover, in the said processing apparatus, it is preferable that a slurry is a slurry which contains any one of a silica abrasive grain, a ceria abrasive grain, an alumina abrasive grain, a zirconia abrasive grain, a silicon carbide abrasive grain, and a diamond abrasive grain, and uses water as a dispersion medium. .
Moreover, it is preferable that the said processing apparatus is a double-sided processing apparatus which can process the upper and lower surfaces of the said glass substrate simultaneously.
Moreover, in the said processing apparatus, it is preferable that the said upper surface plate and the said lower surface plate consist of cast iron.

Further, the present invention is a glass substrate processing method for processing a glass substrate while supplying a slurry or a coolant while holding the glass substrate between an upper surface plate and a lower surface plate,
Provided is a method for processing a glass substrate, characterized in that a slurry or coolant circulating through a circulation path provided with a magnet coated with a peelable coating material is supplied between the upper surface plate and the lower surface plate. To do.
In the processing method, the coating material is preferably a resin, and the resin is polyethylene, polyvinylidene chloride, polypropylene, polyvinylidene fluoride, polyvinyl chloride, polyvinyl alcohol, polyethylene terephthalate, polytrimethylene terephthalate. It is preferably one or more resins selected from the group consisting of polybutylene terephthalate and polyacryl.
In the processing method, the magnet is preferably a permanent magnet.
In the processing method, the magnetic flux density of the permanent magnet is preferably 1000 gauss or more and 14000 gauss or less, more preferably 9000 gauss or more and 14000 gauss or less.
Further, in the processing method, the slurry is a slurry containing any one of silica abrasive grains, ceria abrasive grains, alumina abrasive grains, zirconia abrasive grains, silicon carbide abrasive grains, and diamond abrasive grains and using water as a dispersion medium. preferable.
Moreover, in the said processing method, it is preferable to process the upper and lower surfaces of the said glass substrate simultaneously.
Moreover, it is preferable that the said upper surface plate and the said lower surface plate consist of cast iron.

  Further, the present invention is a method of repeatedly processing a glass substrate using the processing method, after processing the glass substrate using the processing method, after peeling the coating material adhered with magnetic foreign matter from the magnet, A repetitive glass substrate characterized in that the magnet is coated with a peelable coating material to which no magnetic foreign matter is attached, and the glass substrate is processed by the processing method using the magnet coated with the peelable coating material. Provide a method of processing.

  Moreover, this invention provides the glass substrate for magnetic discs or the glass substrate for photomasks manufactured using the said processing method.

  According to the glass substrate processing apparatus, the glass substrate processing method, and the method of repeatedly processing a glass substrate of the present invention, magnetic foreign matters can be easily removed simply by removing the resin, and the foreign matter collecting efficiency is reduced. And the occurrence of piping can be reduced. In addition, since the magnet does not directly contact the slurry or coolant, neither alteration due to oxidation nor reduction in magnetic force occurs. Therefore, the magnetic foreign matter can be removed efficiently and continuously.

It is an external view of the double-sided processing apparatus which concerns on this invention. It is a fragmentary sectional view of the storage chamber which is a part of the double-sided processing apparatus of FIG. It is a flowchart explaining the processing method of the glass substrate which concerns on this invention. It is the photograph of the magnetic foreign material adhering to the magnet. It is a schematic perspective view which shows the process part of a double-sided processing apparatus.

  Hereinafter, an embodiment of a processing apparatus of the present invention will be described in detail with reference to the drawings. In the following description, a double-sided processing apparatus capable of simultaneously processing the upper and lower surfaces of a glass substrate will be exemplified as a processing apparatus.

  As shown in FIG. 5, the double-sided processing apparatus 10 is driven in reverse rotation with respect to each other with a carrier mounting portion having an internal gear 101 and a sun gear 102 that are driven to rotate at a predetermined rotation ratio, and the carrier mounting portion. A processing unit 100 having an upper surface plate 103 and a lower surface plate 104 made of a metal such as cast iron is provided, and a plurality of carriers 107 meshing with the internal gear 101 and the sun gear 102 are mounted on the carrier mounting portion. Yes. The carrier 107 rotates on the center of its own axis and moves in a planetary gear that revolves around the sun gear 102. The carrier 107 is attached to the carrier 107 by this planetary gear movement, and is interposed between the upper surface plate 103 and the lower surface plate 104. Both surfaces of the held glass substrate 105 are simultaneously processed by friction with the upper surface plate 103 and the lower surface plate 104.

  The upper and lower surface plates 103 and 104 are formed by processing both surfaces of the glass substrate 105 with slurry containing abrasive grains supplied between the upper and lower surface plates 103 or 104, or ceramic or resin containing abrasive grains is used for the upper and lower surface plates 103. , 104, and both surfaces of the glass substrate 105 are processed while supplying a coolant mainly composed of water.

  As shown in FIGS. 1 and 2, a storage chamber 11 for storing slurry or coolant is provided at the lower left of the upper and lower surface plates 103 and 104, and the slurry or coolant stored in the storage chamber 11 is pumped by a pumping pump 12. The slurry or coolant supplied between the upper and lower surface plates 103 and 104 through one pipe 13 and discharged between the upper and lower surface plates 103 and 104 is discharged to the storage chamber 11 through the second pipe 14, and the double-side processing apparatus 10. The slurry or coolant is configured to circulate inside. The storage chamber 11 is provided with a stirring blade 15 for stirring the stored slurry or coolant.

  Here, on the circulation path of the slurry or coolant, in this embodiment, a permanent magnet 16 covered with a peelable resin 18 is disposed in the car 17 at the connecting portion between the storage chamber 11 and the second pipe 14. ing. This coating prevents the slurry or coolant from contacting the permanent magnet 16 directly. Moreover, although resin 18 was illustrated as a coating | covering material, it is not limited to this, Arbitrary coating | covering materials which are non-magnetic and waterproof and can be peeled can be used. The covering material may be in any form as long as it can be peeled off, such as a film or bag. Examples of the resin 18 include polyethylene, polypropylene, polyvinylidene chloride, polyvinylidene fluoride, polyvinyl chloride, polyvinyl alcohol, polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, and polyacryl. The magnet is not limited to a permanent magnet, and an electromagnet may be used. Moreover, as long as it is on the circulation path | route of a slurry or coolant, it is not limited to the connection part of the storage chamber 11 and the 2nd piping 14, Arbitrary places, such as in the 1st piping 13, the 2nd piping 14, and the storage chamber 11 Can be arranged.

  As the permanent magnet, a known permanent magnet such as a neodymium magnet or a ferrite magnet can be used. The permanent magnet is preferably 1000 gauss or more and 14000 gauss or less, more preferably 9000 gauss or more and 14000 gauss or less.

In the double-sided processing apparatus 10 of the present embodiment configured as described above, the glass substrate 105 can be lapped and polished while supplying the slurry or coolant stored in the storage chamber 11.
At this time, since the circulating slurry or coolant passes through the vicinity of the permanent magnet 16 disposed at the connection portion between the storage chamber 11 and the second pipe 14 and covered with the resin 18, the metal scrap mixed in the slurry or coolant is removed. It adheres to the surface of the resin 18 by the magnetic force of the permanent magnet 16. Then, the metal waste mixed in the slurry or the coolant is removed by peeling or replacing the resin 18 at regular intervals or when the metal waste accumulates, and the metal waste is mixed in the slurry or the coolant. Thus, scratches generated on the glass substrate 105 can be reduced.

Next, an embodiment of the glass substrate manufacturing method of the present invention will be described with reference to the flowchart of FIG. The manufacturing method of the glass substrate 105 of this embodiment is as follows.
(1) Shape processing step (S1);
(2) Lapping step (S2);
(3) a first cleaning step (S3);
(4) first polishing step (S4);
(5) a second cleaning step (S5);
(6) Second polishing step (S6);
(7) a third cleaning step (S7).

  The shape processing step (S1) is a step of preparing a circular glass substrate 105 (for example, a glass substrate having a diameter of 65 mm), and a through hole (inner hole) is formed at the center of a rectangular plate glass and processed into a circular glass. Cutting step, chamfering step of chamfering the cut circular glass edge (intersection line between main surface and inner peripheral end surface forming through-hole and intersection point of main surface and outer peripheral end surface), inner periphery and outer periphery Polishing to a mirror surface. Here, the main surface refers to an annular portion including the front surface and the back surface of the glass substrate 105.

  In the lapping step (S2), the thickness of the glass substrate 105 is reduced to 110% or less of the final product thickness with the double-sided processing apparatus 10 (699 μm or less when the final plate thickness is 635 μm, 880 μm or less when the final plate thickness is 800 μm). It has a grinding process to prepare.

  Specifically, in the lapping step (S2), in the case of loose abrasive lapping, any one of alumina abrasive grains, zirconia abrasive grains, silicon carbide abrasive grains, and diamond abrasive grains having an average particle diameter of 3.0 μm to 40 μm is contained. Grinding is performed using a metal surface plate, for example, a cast iron surface plate, while supplying a slurry having water as a main dispersion medium. In the case of a fixed abrasive wrap, ceramic or resin containing any one of alumina abrasive grains, zirconia abrasive grains, silicon carbide abrasive grains, and diamond abrasive grains having an average particle diameter of 3.0 μm to 40 μm is formed on the upper and lower sides of the double-side processing apparatus 10. The upper and lower surfaces of the glass substrate 105 are ground while flowing a coolant which is fixed to the surface plates 103 and 104 and mainly contains water.

  Subsequently, in the first cleaning step (S3), the glass substrate 105 that has finished the lapping step (S2) is cleaned. For example, ultrasonic cleaning using water, detergent, strong acid or strong alkali is performed.

  In the first polishing step (S4), the main surface of the glass substrate 105 is polished while the ceria slurry is supplied by the double-sided processing apparatus 10, so that fine irregularities formed on the main surface of the sheet glass in the lapping step The shape can be reduced to obtain a mirrored main surface. More specifically, both surfaces of a hard foamed urethane pad or a suede-like urethane pad attached to the upper and lower surface plates 103 and 104 using ceria slurry in which ceria abrasive grains having an average particle size of 0.1 μm to 2.0 μm are dispersed in water. The glass substrate 105 is polished using the processing apparatus 10 to perform mirror finishing.

  Subsequently, in the second cleaning step (S5), the glass substrate after the first polishing step (S4) is cleaned. For example, ultrasonic cleaning using water, detergent, strong acid or strong alkali is performed.

  In the second polishing step (S6), the main surface of the glass substrate 105 is polished while supplying silica slurry to the double-sided processing apparatus 10, thereby adjusting the arithmetic average roughness (Ra) of the main surface to 0.3 nm or less. . More specifically, the double-sided processing apparatus 10 in which a suede-like urethane pad is attached to the upper and lower surface plates 103 and 104 using a silica slurry in which colloidal silica abrasive grains having an average particle diameter of 0.005 μm to 0.1 μm are dispersed in water. The glass substrate 105 is polished to adjust the roughness.

  Subsequently, in the third cleaning step (S7), the glass substrate 105 after the second polishing step (S6) is cleaned. For example, ultrasonic cleaning using water, detergent, strong acid or strong alkali is performed.

  Here, after a series of processing methods of the glass substrate 105 of (S1) to (S7) are repeated a predetermined number of times, the resin 18 that covers the permanent magnet 16 is peeled off, and then the resin 18 is coated again with a new resin 18. Exchange is performed, and the adhering metal waste is removed together with the resin 18.

  In this way, by replacing the resin 18 during repeated use of the double-sided processing apparatus 10, it is possible to easily clean the magnetic foreign matter without causing a decrease in foreign matter collection efficiency and clogging of piping. . Further, since the permanent magnet 18 does not directly contact the slurry or the coolant, neither alteration due to oxidation nor reduction in magnetic force occurs. Therefore, the magnetic foreign matter can be removed efficiently and continuously.

  In addition, the manufacturing method of the glass substrate in this invention is not limited to such a thing, What is necessary is just to provide the lapping process or polishing process of at least 1 time, an additional shape processing process, the polishing process of a main surface, a washing process Further, a strengthening process or the like may be provided.

  In addition, the glass substrate manufacturing method of the present invention can be used in any slurry and coolant glass processing apparatus, but the double-sided processing apparatus 10 capable of simultaneously processing the upper and lower surfaces of the glass substrate is particularly compared with a single-sided processing apparatus. Therefore, since the processing resistance is high and foreign matters are likely to be generated from the gears and the upper and lower surface plates 103 and 104, they are more preferably used.

  Moreover, the manufacturing method of the glass substrate of this invention can also be used for the glass processing apparatus using the upper and lower surface plates 103 and 104 of any abrasive grain and any material. In a double-sided processing machine that uses a slurry containing either alumina abrasive grains or silicon carbide abrasive grains and lapping with a cast iron platen, the cast iron platen wears more severely and a large amount of metal wear debris is generated. Preferably used.

  In addition, the glass substrate processing apparatus and manufacturing method of the present invention can be used for manufacturing glass substrates for magnetic disks, photomasks, liquid crystal televisions, and flat lenses. It is preferably used for the production of glass substrates for magnetic disks and photomasks that affect the magnetic field.

Hereinafter, the present invention will be specifically described by giving examples and comparative examples. In addition, this invention is not limited to the structure of these Examples.
[Magnetic foreign matter collection performance confirmation test]
In order to confirm the collection performance of the magnetic foreign matter, the following magnetic foreign matter collection performance confirmation test was performed using a large double-sided processing device (22B: a double-sided processing device capable of mounting a 22-inch carrier). For the test, a glass substrate for a magnetic disk having a diameter of 2.5 inches and a thickness of about 800 μm was prepared. The slurry used was a slurry in which alumina abrasive grains having an average diameter of about 7 μm were dispersed in water, and the upper and lower surface plates were cast iron surface plates with grooves. Lapping was performed so that the processing pressure was 7 kPa and the thickness was about 670 μm.

  The lapped substrate was then cleaned and then polished with ceria slurry to give a mirror-finished substrate having a thickness of about 640 μm. Thereafter, cleaning was performed again, and after the roughness was adjusted by polishing with silica slurry, final cleaning was performed. After the final cleaning, all substrates were inspected for defects. This series of processing steps is hereinafter referred to as one batch.

  In Example 1, as shown in FIG. 2, a 9000 Gauss neodymium magnet wrapped with a commercially available polyvinylidene chloride film was disposed at the connecting portion between the storage chamber 11 and the second pipe 14. In Comparative Example 1, the same conditions as in Example 1 were used except that a 9000 Gauss neodymium magnet not coated with resin was placed in the same place as above. In Example 2, the same conditions as in Example 1 were used except that a 1300 gauss ferrite magnet coated with a polyvinylidene chloride film was disposed at the same place as in Example 1. In Comparative Example 2, the conditions were the same as in Example 1 except that no magnet was disposed on the circulation path.

  In Examples 1 and 2, the magnet polyvinylidene chloride film was replaced every 20 batches after processing, the adhered magnetic foreign matter was dried, and the weight was also measured. For Comparative Example 1, the magnet was washed with water every 20 batches after processing, and the adhered magnetic foreign matter dropped by washing was dried and the weight was measured. Table 1 shows the results of the magnetic foreign matter collecting performance confirmation test in the lapping process.

  When the neodymium magnet of Example 1 was covered with a polyvinylidene chloride film, about 20 g of magnetic foreign matters could be removed continuously. In Comparative Example 1, the magnetic foreign matter adhering to the magnet could not be removed as compared with Example 1, so that the magnetic foreign matter gradually became difficult to adhere to the magnet, and the magnetic foreign matter could hardly be removed after 41 batches. In Example 2, the amount of adhered magnetic foreign matter was smaller than that of the neodymium magnet, but it was possible to remove magnetic foreign matter stably and continuously as in Example 1.

  Table 2 shows final scratch occurrence rates in Examples 1 and 2 and Comparative Examples 1 and 2. The scratch occurrence rate represents the number of glass substrates on which scratches have been detected out of the total number of glass substrates examined.

  In Example 1, the scratch occurrence rate was reduced by 0.8% compared to Comparative Example 1 in which the magnet was not covered with the polyvinylidene chloride film. In Example 2, the scratch occurrence rate was reduced by 0.3% compared to Comparative Example 1.

  FIG. 4 shows an example of an electron micrograph of the deposit confirmed in Example 1. In the first embodiment, it is possible to efficiently and continuously remove such magnetic foreign substances that cause such scratches.

  From the above results, according to the present invention, it is possible to easily clean the magnetic foreign matter by simply peeling off and replacing the resin, and the foreign matter collecting efficiency is not lowered and the piping is not clogged. In addition, since the magnet does not directly contact the slurry or coolant, neither alteration due to oxidation nor reduction in magnetic force occurs. Therefore, the magnetic foreign matter can be removed efficiently and continuously.

  The present invention is not limited to the embodiment described above, and can be implemented in various forms without departing from the gist of the present invention.

10 Double-sided processing equipment (processing equipment)
16 Permanent magnet (magnet)
18 Resin (coating material)
103 Upper surface plate 104 Lower surface plate 105 Glass substrate

Claims (20)

  A glass substrate processing apparatus for processing a glass substrate held between an upper surface plate and a lower surface plate while supplying slurry or coolant, and a covering material that can be peeled off in a circulation path through which the slurry or coolant circulates An apparatus for processing a glass substrate, comprising: a magnet coated with   The processing apparatus according to claim 1, wherein the covering material is a resin.   One or more resins selected from the group consisting of polyethylene, polyvinylidene chloride, polypropylene, polyvinylidene fluoride, polyvinyl chloride, polyvinyl alcohol, polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate and polyacrylic. The glass substrate processing apparatus according to claim 2, wherein:   The processing apparatus according to claim 1, wherein the magnet is a permanent magnet.   The glass substrate processing apparatus according to claim 4, wherein the permanent magnet has a magnetic flux density of 1000 gauss or more and 14000 gauss or less.   6. The glass substrate processing apparatus according to claim 5, wherein the permanent magnet has a magnetic flux density of 9000 gauss or more and 14000 gauss or less.   The slurry is a slurry containing any one of silica abrasive grains, ceria abrasive grains, alumina abrasive grains, zirconia abrasive grains, silicon carbide abrasive grains, and diamond abrasive grains in which water is used as a dispersion medium. 6. The glass substrate processing apparatus according to any one of 6 above.   The said processing apparatus is a double-sided processing apparatus which can process the upper and lower surfaces of the said glass substrate simultaneously, The processing apparatus of the glass substrate in any one of Claims 1-7 characterized by the above-mentioned.   The said upper surface plate and the said lower surface plate consist of cast iron, The processing apparatus of the glass substrate in any one of Claims 1-8 characterized by the above-mentioned. A glass substrate processing method for processing a glass substrate while supplying a slurry or coolant while holding the glass substrate between an upper surface plate and a lower surface plate,
A method for processing a glass substrate, comprising supplying a slurry or coolant circulating through a circulation path in which a magnet coated with a peelable coating material is disposed between the upper surface plate and the lower surface plate.   The method for processing a glass substrate according to claim 10, wherein the covering material is a resin.   One or more resins selected from the group consisting of polyethylene, polyvinylidene chloride, polypropylene, polyvinylidene fluoride, polyvinyl chloride, polyvinyl alcohol, polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate and polyacrylic. The method for processing a glass substrate according to claim 11, wherein:   The method for processing a glass substrate according to claim 10, wherein the magnet is a permanent magnet.   The method for processing a glass substrate according to claim 13, wherein the permanent magnet has a magnetic flux density of 1000 gauss or more and 14000 gauss or less.   The glass substrate processing method according to claim 14, wherein the permanent magnet has a magnetic flux density of 9000 gauss or more and 14000 gauss or less.   The slurry is a slurry containing any one of silica abrasive grains, ceria abrasive grains, alumina abrasive grains, zirconia abrasive grains, silicon carbide abrasive grains, and diamond abrasive grains in which water is used as a dispersion medium. The processing method of the glass substrate in any one of 15.   The method for processing a glass substrate according to claim 10, wherein upper and lower surfaces of the glass substrate are processed simultaneously.   The said upper surface plate and the said lower surface plate consist of cast iron, The processing method of the glass substrate in any one of Claims 10-17 characterized by the above-mentioned.   A method of repeatedly processing a glass substrate using the glass substrate processing method according to any one of claims 10 to 18, wherein after the glass substrate is processed using the processing method, the magnetic foreign matter adheres thereto. The material is peeled off from the magnet, the magnet is covered with a peelable coating material to which no magnetic foreign matter is adhered, and the glass substrate is processed by the processing method using the magnet covered with the peelable coating material. A method of processing a glass substrate repeatedly characterized by the following.   A glass substrate for a magnetic disk or a glass substrate for a photomask manufactured using the method for processing a glass substrate according to claim 10.