JP2012203921A - Manufacturing method for glass substrate for magnetic disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for a glass substrate for a magnetic disk with high strength and being less likely to cause head crash when being mounted on a hard disk.SOLUTION: A manufacturing method for a glass substrate for a magnetic disk includes at least the following: a coring step of forming a hole in the center of a glass substrate precursor with a disk-like shape manufactured by a direct press method; and an inside and outside processing step of chamfering an inner peripheral end face and an outer peripheral end face of the glass substrate precursor. A chemical processing step of processing a surface of the glass substrate precursor is included between the coring step and the inside and outside processing step.

Description

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

  In recent years, in a hard disk drive (HDD), the recording capacity of a magnetic recording medium has been increased. Along with this, the gap (head flying height) between the magnetic recording medium and the head for reading and writing the recording has decreased to a level of several nm. When the head flying height decreases, the head and the magnetic recording medium collide with each other to cause a phenomenon called head crash, which easily causes a read / write error of the hard disk.

  There are several possible causes of the above error. One of the causes is the effect of fluttering. Fluttering means the amount of amplitude (surface runout) when a magnetic recording medium is rotated at high speed, and is roughly classified into two types. One is surface runout (RRO: Repeatable Run Out) that repeats periodically and the other is irregular runout (NRRO: Non Repeatable Run Out).

  RRO is less likely to cause a head crash because the head can follow. On the other hand, NRRO causes a head crash because the head cannot follow. In recent years, in a head having a DFH mechanism, the flying height of the head is becoming lower and the head crash due to NRRO increases. Therefore, in order to reduce the head crash of the hard disk, it is necessary to reduce NRRO.

  By the way, in recent years, hard disks have been used for various purposes, and accordingly, hard disks are required to have impact resistance. For example, there are two types of substrates for recording media mounted on a hard disk: aluminum and glass. Recently, glass having excellent impact resistance has been frequently used.

  Glass is theoretically high in strength, but easily breaks due to minute cracks present on the surface of the glass. As a countermeasure against this, for example, in Japanese Unexamined Patent Application Publication No. 2007-102842 (Patent Document 1), an attempt to improve the strength of the glass substrate by removing minute cracks on the surface of the glass substrate using an etching solution such as HF. Has been made.

JP 2007-102842 A

  However, when a magnetic disk manufactured using the glass substrate of Patent Document 1 is mounted on a hard disk and used, head crashes are likely to occur.

  The present invention has been made under such circumstances, and an object of the present invention is to provide a method for manufacturing a glass substrate for a magnetic disk that has high strength and is less likely to cause head crash when mounted on a hard disk. There is.

  The present inventors can confirm that the cause of the head crash in the glass substrate of Patent Document 1 is due to the occurrence of fluttering of NRRO during high-speed rotation. The knowledge that the shape of the end surface of the glass substrate for disks is not uniform was obtained. Further investigations have been made based on this finding. As a result, the manufacturing method disclosed in Patent Document 1 finds that there is a problem in the order of the manufacturing steps, and the magnetic disk glass substrate of the present invention is modified by changing the steps. The manufacturing method was completed.

  That is, the method for producing a glass substrate for a magnetic disk of the present invention is a production method using a disk-shaped glass substrate precursor produced by a direct press method, and a coring step of making a hole in the center of the glass substrate precursor. And an inner and outer processing step for chamfering the inner peripheral end surface and the outer peripheral end surface of the glass substrate precursor, and a chemical processing step for processing the surface of the glass substrate precursor between the coring step and the inner and outer processing step. It is characterized by that.

  In the chemical treatment step, it is preferable to remove a thickness of 5 to 30 μm from the surface of the glass substrate precursor. In the chemical treatment step, it is preferable to remove a thickness of 12 to 20 μm from the surface of the glass substrate precursor.

  The method for producing a glass substrate for magnetic disk of the present invention has the above-described configuration, and can produce a glass substrate for magnetic disk that has high strength and is less likely to cause head crash when mounted on a hard disk. Excellent effect.

It is a perspective view which shows an example of the glass substrate for magnetic discs manufactured by the manufacturing method of this invention. It is a flowchart which shows an example of the order of the process of the manufacturing method of the glass substrate for magnetic discs of this invention.

  Hereinafter, a glass substrate for a magnetic disk and a manufacturing method thereof according to the present invention will be described with reference to the drawings and a flowchart. Note that dimensional relationships such as length, width, thickness, and depth are changed as appropriate for clarity and simplification of the drawings, and do not represent actual dimensional relationships.

<Glass substrate for magnetic disk>
FIG. 1 is a perspective view showing an example of a glass substrate for a magnetic disk manufactured by the manufacturing method of the present invention. The glass substrate for a magnetic disk manufactured by the manufacturing method of the present invention is used as a substrate for an information recording medium in an information recording apparatus such as a hard disk drive apparatus. Such a glass substrate for a magnetic disk has a disk shape as shown in FIG. 1, and a hole 1H is formed at the center thereof. The surface of the glass substrate 1 for magnetic disks means the front main surface 1A, the back main surface 1B, the inner peripheral end surface 1C, and the outer peripheral end surface 1D.

  The size and shape of the magnetic disk glass substrate 1 of the present invention are not particularly limited and are, for example, 0.8 inch, 1.0 inch, 1.8 inch, 2.5 inch, or 3.5 inch. The thickness of the magnetic disk glass substrate 1 is preferably 0.30 to 2.2 mm, for example, from the viewpoint of preventing breakage. In addition, the thickness of the glass substrate 1 for magnetic disks is calculated by the average of the values measured at a plurality of arbitrary points to be pointed on the glass substrate. A typical example of the magnetic disk glass substrate 1 of the present invention is as follows. The magnetic disk glass substrate has an outer diameter of about 64 mm, an inner diameter of about 20 mm, and a thickness of about 0.8 mm. In general, a 2.5-inch hard disk uses a glass substrate for a magnetic disk having an outer diameter of 65 mm.

Aluminosilicate glass is preferably used as the material constituting the magnetic disk glass substrate of the present invention. The composition of this aluminosilicate glass is 58 mass% to 75 mass% SiO ₂ , 5 mass% to 23 mass% Al ₂ O ₃ , 3 mass% to 10 mass% Li ₂ O, 4 mass% to 13 mass. % Na ₂ O as a main component.

<Method for manufacturing glass substrate for magnetic disk>
The method for producing a glass substrate for a magnetic disk according to the present invention uses a disk-shaped glass substrate precursor produced by a direct press method, and comprises a coring step of making a hole in the center of the glass substrate precursor, and a glass At least an inner peripheral end surface and an inner / outer processing step of chamfering the outer peripheral end surface of the substrate precursor, and a chemical processing step of processing the surface of the glass substrate precursor between the coring step and the inner / outer processing step. And

  By performing the internal / external processing step after performing the chemical processing step as in the present invention, the glass substrate for magnetic disk whose end face is non-uniform in the chemical processing step can be made uniform in the internal / external processing step. A glass substrate for a magnetic disk in which NRRO hardly occurs can be produced. The glass substrate for a magnetic disk produced as described above exhibits an excellent property that NRRO does not easily occur and therefore head crash does not easily occur.

  The method for producing a glass substrate for a magnetic disk of the present invention can include other steps as long as the chemical treatment step is performed between the coring step and the inside / outside processing step. Here, as other processes, for example, a direct pressing process for processing molten glass into a disk shape, a lapping process for adjusting the parallelism and thickness of the glass substrate precursor, and the polishing performed in the rough polishing process, the glass substrate precursor. Examples include a polishing step for polishing to improve the smoothness of the glass, a cleaning step for cleaning both the front and back surfaces of the glass substrate precursor, and the like.

  In addition, the manufacturing method of the glass substrate for magnetic discs of this invention is limited to what is manufactured by the direct press method, and what is manufactured by the float glass process is not included. This is because when a glass substrate for a magnetic disk is manufactured by the float process, microcracks are unlikely to be generated on the surface, so that it is not necessary to improve the strength by performing a chemical treatment process.

  Below, each process when producing the glass substrate for magnetic discs of this invention according to the flowchart of FIG. 2 is demonstrated. In addition, you may perform simple washing | cleaning suitably other than each step S10-S90 shown by FIG. 2, as long as it includes a coring process, a chemical treatment process, and an internal / external process in this order, A lapping step, a cleaning step, and a polishing step may be further included between the respective steps, and the order of other steps may be appropriately changed.

(Direct press process: Step S10)
First, a molten glass is prepared by melting a glass material. The molten glass is poured into a lower mold and press-formed with an upper mold and a barrel mold to obtain a disk-shaped glass substrate precursor. The process of obtaining the glass substrate precursor from the molten glass in this way is called a direct press process.

(Coring process: Step S20)
Next, a hole is made in the central portion of the glass substrate precursor in the coring process. In the drilling, a hole is drilled in the center by grinding with a core drill or the like equipped with a diamond grindstone or the like in the cutter part. The size of the hole can be appropriately changed depending on the outer diameter of the glass substrate precursor. For example, a hole having an inner diameter of 20 mm (the diameter of the hole 1H in the center) is formed at the center of the glass substrate precursor having an outer shape of 65 mm. Open.

(Rough wrapping process: Step S30)
A lapping process is performed on both the front and back surfaces of the glass substrate precursor. Here, the rough lapping is performed by, for example, a double-sided lapping apparatus. As a result, the overall shape, parallelism, flatness and thickness of the glass substrate precursor can be preliminarily adjusted.

(Chemical treatment process: Step S40)
The surface and end face of the glass substrate precursor are etched by immersing the glass substrate precursor in an etching solution composed of a mixture of hydrogen fluoride and water. Thus, by etching the surface of the glass substrate precursor, defects and cracks formed on the surface of the glass substrate precursor in the rough lapping step can be removed, and the strength of the glass substrate precursor can be improved. . Examples of the etching solution include HF, NH ₄ F, NaF, and the like, and may be used in combination with an acid such as sulfuric acid or nitric acid.

  In addition, the degree of etching changes for every part of the end surface of the glass substrate precursor during the immersion in the etching solution or during the pulling operation after the immersion. As a result, the shape of the end portion of the glass substrate precursor is not uniform and minute waviness occurs, and the inner and outer diameter portions are not concentric circles, but these defects are uniformly adjusted by the inner and outer processing steps described later. The

  The conventional method for manufacturing a glass substrate for a magnetic disk has performed a chemical treatment step after an inner / outer processing step, which will be described later, so that the nonuniformity and minute waviness of the end surface of the glass substrate precursor generated in the chemical treatment step is corrected. I couldn't. For this reason, when the disk is clamped (attached) to the hard disk, irregular fluttering has occurred due to the displacement of the clamping force. The present invention solves this problem by performing a chemical treatment step before the internal and external processing steps.

  In the present invention, in the chemical treatment step, it is preferable to remove 5 to 30 μm from the surface of the glass substrate precursor, more preferably 12 to 25 μm, and even more preferably 12 to 20 μm. That is. If it is less than 5 μm, microcracks on the surface of the glass substrate precursor cannot be removed. Conversely, if it exceeds 30 μm, the glass substrate precursor is etched unevenly, resulting in unevenness in the glass substrate precursor. Will occur. It should be noted that unevenness caused by the chemical treatment process is less likely to occur when the surface of the glass substrate precursor is mirror-finished because the wettability of the substrate is improved, but the glass substrate precursor is not mirror-finished. Likely to happen. As the thickness of the etching, a value calculated by the difference in the inner diameter of the glass substrate precursor is adopted.

(Internal / external machining process: Step S50)
Next, in the inside / outside processing step, chamfering of the outer peripheral end surface and the inner peripheral end surface of the glass substrate precursor is performed. Thereby, the minute nonuniformity of the end surface of the glass substrate precursor generated in the chemical treatment process is removed.

(Fine wrapping process: Step S60)
Next, in the fine lapping process, the front and back surfaces of the glass substrate precursor are ground using a fixed abrasive polishing pad. Such a fine lapping process can be ground using a known grinding machine called a double-side grinding machine using a planetary gear mechanism. This double-sided grinding machine is equipped with a disk-shaped upper and lower surface plate arranged in parallel with each other in parallel, and the front and back surfaces of the glass substrate precursor are placed on the surfaces facing the upper surface plate and the lower surface plate, respectively. A plurality of diamond pellets for grinding are attached.

  Between the upper surface plate and the lower surface plate, there are a plurality of carriers that rotate in combination with an internal gear provided in an annular shape on the outer periphery of the lower surface plate and a sun gear provided around the rotation axis of the lower surface plate. . The carrier is provided with a plurality of holes, and the glass substrate precursor is fitted into the holes and arranged. The upper surface plate, the lower surface plate, the internal gear, and the sun gear can be operated by separate driving, and the upper surface plate and the lower surface plate rotate in opposite directions.

  Then, the carrier sandwiched between the surface plates via the diamond pellets revolves in the same direction as the lower surface plate with respect to the center of rotation of the surface plate while rotating while holding a plurality of glass substrate precursors. In the grinding machine operating in this way, the front and back surfaces of the glass substrate precursor can be ground by supplying a grinding liquid between the upper surface plate and the glass substrate precursor and between the lower surface plate and the glass substrate precursor. it can.

When using this double-side polishing machine, the weight of the surface plate applied to the glass substrate precursor and the number of rotations of the surface plate are adjusted as appropriate according to the desired grinding state. In the fine wrapping process, it is preferable to perform the wrapping in two steps of the first wrapping process and the second wrapping process. The weight in the first wrapping step and the second wrapping step is preferably 60 g / cm ² to 120 g / cm ² . Further, it is preferable that the rotation speed of the surface plate is about 10 rpm to 30 rpm, and the rotation speed of the upper surface plate is about 30% to 40% slower than the rotation speed of the lower surface plate. At the time when the second lapping process is completed, defects such as large undulation, chipping and cracking of the glass substrate precursor are removed.

  Increasing the weight by the surface plate or increasing the rotation speed of the surface plate will increase the amount of grinding of the glass substrate precursor, but if the load is increased too much, the surface roughness of the glass substrate precursor will deteriorate. Therefore, it is not preferable. Further, if the rotation speed of the surface plate is too fast, the flatness will not be good. Moreover, even if the load is too small or the rotation speed of the surface plate is too slow, the amount of grinding is reduced and the production efficiency is lowered.

  As for the surface roughness of the main surface of the glass substrate precursor after finishing the fine lapping step, Ra is preferably 0.05 to 0.4 μm, and the flatness of the main surface is 7 to 10 μm. It is preferable. By setting it as such a surface state, the polishing efficiency in the subsequent first polishing step can be enhanced.

(End face polishing process: Step S70)
Subsequently, in the end face polishing step, the outer peripheral end face and the inner peripheral end face of the glass substrate precursor are polished by a brush polishing method using a slurry (free abrasive grains) containing cerium oxide abrasive grains as polishing abrasive grains. In the brush polishing method, the outer peripheral end face and the inner peripheral end face are polished while rotating the glass substrate precursor. The inner peripheral end face of the glass substrate precursor is processed into a mirror surface state by further polishing the inner peripheral end face with a magnetic polishing method. Finally, the surface of the glass substrate precursor is washed with water.

(Main surface polishing step: Step S80)
In the main surface polishing step, the front and back surfaces of the glass substrate precursor are polished by the first polishing step and the second polishing step. The first polishing process is performed to remove scratches and distortions remaining on the front and back surfaces of the glass substrate precursor in the fine lapping process, and the second polishing process is performed to mirror-process the front and back surfaces of the glass substrate precursor.

  First, in a 1st grinding | polishing process, the polishing pad whose polisher is a suede pad is set to said double-side polisher, and the front and back of a glass substrate precursor are grind | polished. And the abrasive | polishing agent adhering to the surface of the said glass substrate precursor is removed by washing | cleaning.

  Then, in a 2nd grinding | polishing process, the front and back of a glass substrate precursor are grind | polished using the polishing pad which is a soft polisher (suede) with respect to a glass substrate precursor. In addition, as an abrasive | polishing agent used at a 2nd grinding | polishing process, it is preferable to use a silica abrasive grain finer than the cerium oxide used at the 1st grinding | polishing process.

(Washing process: Step S90)
It is preferable to wash and dry the glass substrate precursor after the above polishing with a neutral detergent and pure water. By performing such cleaning, foreign substances adhering to the glass substrate precursor can be washed away, the surface of the magnetic disk glass substrate can be stabilized, and excellent long-term storage stability can be achieved. A glass substrate for a magnetic disk can be produced as described above. A magnetic disk can be obtained by further performing a magnetic thin film forming step on the magnetic disk glass substrate thus produced.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

<Example 1>
In this example, a glass substrate for a magnetic disk was manufactured by performing the following steps in order.

(Direct press process)
First, molten glass was prepared by melting a glass material. The molten glass was poured into a lower mold and directly pressed using an upper mold and a barrel mold to obtain a disk-shaped glass substrate precursor having a diameter of 66 mmφ and a thickness of 1.2 mm. Aluminosilicate glass was used as the glass material.

(Coring process)
Next, a hole was made by grinding the central portion of the glass substrate precursor with a core drill having a diamond grindstone or the like in the cutter portion. In this way, a hole having an inner diameter of 20 mm (diameter of the hole 1H in the central part) was formed in the central part of the glass substrate precursor having an outer diameter of 65 mm.

(Coarse lapping process)
Next, the glass substrate precursor is set in a double-sided wrapping apparatus, and alumina abrasive grains having a particle size of # 400 (particle size of about 40 to 60 μm) are used, and the load on the surface plate on alumina is set to about 100 kg. The front and back surfaces of the glass substrate precursor were polished. The glass substrate precursor thus housed in the carrier had a surface accuracy of 0 μm to 1 μm on both sides and a surface roughness Rmax of about 6 μm.

(Chemical treatment process)
The surface and end surface of the glass substrate precursor were etched by immersing the glass substrate precursor in an etching solution. In this example, the thickness of 10 μm was removed from the surface of the glass substrate precursor using a 5 mass% hydrogen fluoride aqueous solution as an etching solution. The thickness after removing the glass substrate precursor was calculated based on the change in the inner diameter before and after the chemical treatment.

(Internal / external machining process)
Next, chamfering of the outer peripheral end surface and the inner peripheral end surface of the glass substrate precursor was performed. As a result, the surface roughness of the end surface of the glass substrate precursor was about 2 μm in Rmax.

(Fine wrapping process)
Next, in the fine lapping process, both the front and back surfaces of the glass substrate precursor were set in a double-side grinding machine using a planetary gear mechanism. Then, using a diamond sheet, the weight of the platen applied to the glass substrate precursor is changed from 60 g / cm ² to 120 g / cm ² , the rotation speed of the platen is changed from 10 rpm to 30 rpm, and the rotation speed of the upper platen is decreased. The front and back surfaces of the glass substrate precursor were polished at a rate slower by about 30% to 40% than the platen rotation speed. Thus, lapping was performed until the surface roughness Ra of the main surface of the glass substrate precursor was 0.1 μm or less and the flatness was 7 μm or less.

(End face polishing process)
Subsequently, the outer peripheral end surface and the inner peripheral end surface of the glass substrate precursor were polished while rotating the glass substrate precursor by a brush polishing method using a slurry (free abrasive particles) containing cerium oxide abrasive grains as polishing abrasive grains. . Here, polishing was performed until the surface roughness of the outer peripheral end face and the inner peripheral end face of the glass substrate precursor was about 0.4 μm in Rmax and about 0.1 μm in Ra.

  The above-mentioned inner peripheral side end face was further polished by a magnetic polishing method to be processed into a mirror surface state that prevents generation of particles and the like. And after grind | polishing the inner peripheral end surface in this way, the surface of the glass substrate precursor was wash | cleaned with water.

(Main surface polishing process)
In the main surface polishing step, first, a first polishing step for removing scratches and distortions remaining in the fine lapping step was performed using the above-described double-side polishing apparatus. In this first polishing step, the front and back surfaces of the glass substrate precursor were polished under the following conditions using a polishing pad whose polisher was a suede pad.

Polishing liquid: Cerium oxide (average particle diameter 1.3 μm) + water load: 80 to 100 g / cm ²
Polishing time: 30 minutes to 50 minutes Removal method: 35 μm to 45 μm
Next, the abrasive | polishing agent adhering to the surface of the said glass substrate precursor was removed by washing | cleaning. The cleaning method was performed by irradiating an ultrasonic wave of 80 kHz using a liquid in which 1% by mass of HF and 3% by mass of sulfuric acid were mixed. Thereafter, ultrasonic cleaning was performed by irradiating 120 kHz ultrasonic waves with a neutral detergent, and finally, rinsing with pure water was performed to dry IPA.

  Then, the front and back of the glass substrate precursor were grind | polished with respect to the glass substrate precursor using the polishing pad which is a soft polisher (suede) (2nd grinding | polishing process). In addition, as an abrasive | polishing agent used at a 2nd grinding | polishing process, the silica abrasive grain finer than the cerium oxide used at the 1st grinding | polishing process was used.

(Washing process)
The glass substrate precursor after the polishing treatment was washed with a neutral detergent and pure water and dried. As described above, the magnetic disk glass substrate of this example was produced.

<Examples 2 to 7>
Similar to Example 1 except that the thickness for removing the surface of the glass substrate precursor in the chemical treatment step is changed to the thickness described in the column “Removal Amount” in Table 1. The glass substrate for magnetic disks of Examples 2-7 was produced by the method.

<Comparative Example 1>
In Comparative Example 1, the chemical treatment step was performed after the internal and external processing steps were performed, as in the conventional method for producing a glass substrate for magnetic disks. A glass substrate for a magnetic disk was produced by the same method as in Example 1 except that this was different.

<Comparative example 2>
In Comparative Example 2, a glass substrate for magnetic disk was produced by the same method as in Example 1 except that the chemical treatment step was not performed.

<Evaluation>
The strength and the number of errors of the glass substrates for magnetic disks prepared in the above examples and comparative examples were evaluated by the following methods.

(Strength)
The strength of the glass substrate for a magnetic disk produced in each example and each comparative example was evaluated by a ring test, and the result is shown in the “strength” column of Table 1. Here, the strength evaluation by the annular test is carried out by setting a magnetic disk glass substrate in a compression test apparatus (product name: Tensilon RTG-1310 (manufactured by A & D)), and It was calculated from the pressure (kgf) when the glass substrate for a magnetic disk was broken when the ball was placed on the inner diameter portion and the pressure was gradually increased from above.

(Number of errors)
After a magnetic film was formed on the surface of the glass substrate for magnetic disk produced in each example and each comparative example by sputtering, it was mounted on a hard disk drive having a DFH mechanism, and read / write errors on the entire disk surface were evaluated. This error was evaluated by counting errors where the read / write error area was 0.5 μm or more when the entire disk surface was read / written. Although errors occur in units of bits, errors due to head crashes occur in a certain number of bits, so an error area of 0.5 μm or larger was evaluated as the cause of head crashes. It is considered that the smaller the number of errors, the less likely the head crash occurs.

  As is clear from Table 1, the magnetic disk glass substrates of Examples 1 to 7 have high strength and are less likely to cause head crash, whereas the magnetic disk glass substrate of Comparative Example 1 has an error due to head crash. It was easy to occur. Further, the glass substrate for magnetic disk of Comparative Example 2 was very low in strength and easily broken.

  In Examples 1-7, the non-uniformity of the end face of the glass substrate precursor generated in the chemical treatment process can be adjusted in the internal and external process steps by performing the internal and external machining steps after the chemical treatment step. It is considered that the occurrence of NRRO was suppressed and head crushing was difficult to occur.

  On the other hand, in Comparative Example 1, since the chemical treatment is performed after the inside / outside processing step, the non-uniformity of the end face of the glass substrate precursor generated by the chemical treatment cannot be made uniform, and NRRO is It is considered that the head crash frequently occurred. Further, in Comparative Example 2, since no chemical treatment was performed, cracks remained on the surface of the magnetic disk glass substrate and were easily broken.

  Therefore, it was shown that the glass substrate for magnetic disk manufactured according to the manufacturing method of the present invention has high strength and hardly causes head crash. In particular, as shown in Examples 4 to 6, when the amount of the glass substrate precursor removed from the surface by the chemical treatment step was 12 to 30 μm, the strength of the magnetic disk glass substrate was significantly improved.

  Although the embodiments and examples of the present invention have been described as described above, it is also planned from the beginning to appropriately combine the configurations of the above-described embodiments and examples.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1 Glass substrate precursor, 1A Front main surface, 1B Back main surface, 1C Inner peripheral end surface, 1D Outer peripheral end surface, 1H hole.

Claims (3)

A method for producing a glass substrate for a magnetic disk using a disk-shaped glass substrate precursor produced by a direct press method,
A coring step of making a hole in the center of the glass substrate precursor;
Including at least an inner and outer processing step of chamfering the inner peripheral end surface and the outer peripheral end surface of the glass substrate precursor,
A method for manufacturing a glass substrate for a magnetic disk, comprising a chemical treatment step of treating a surface of the glass substrate precursor between the coring step and the inside / outside processing step.   The said chemical treatment process is a manufacturing method of the glass substrate for magnetic discs of Claim 1 which removes thickness of 5-30 micrometers from the surface of the said glass substrate precursor.   The said chemical treatment process is a manufacturing method of the glass substrate for magnetic discs of Claim 1 or 2 which removes thickness of 12-20 micrometers from the surface of the said glass substrate precursor.

Images