WO2013099656A1

WO2013099656A1 - Glass substrate for information recording medium and method for producing same

Info

Publication number: WO2013099656A1
Application number: PCT/JP2012/082485
Authority: WO
Inventors: 小松　隆史
Original assignee: コニカミノルタ株式会社
Priority date: 2011-12-27
Filing date: 2012-12-14
Publication date: 2013-07-04

Abstract

In the present invention, the inner peripheral edge surfaces (4) of a first number of glass element plates (1) are ground using a grinding surface (41), and the inner peripheral edge surfaces (4) of a second number of glass element plates (1) are ground using an abrasive surface (42). When stacking a plurality of glass element plates (1) and abrading the inner peripheral edge surfaces (4) thereof, the glass element plates (1) from among the first number of glass element plates (1) and the glass element plates (1) from among the second number of glass element plates are caused not to be intermingled with each other.

Description

Glass substrate for information recording medium and manufacturing method thereof

The present invention relates to a glass substrate for information recording media and a method for manufacturing the same, and in particular, a glass substrate for information recording media mounted as part of an information recording medium in an information recording device such as a hard disk drive (HDD), and It relates to the manufacturing method.

An information recording medium (magnetic disk) is mounted inside an information recording device such as a hard disk drive. The information recording medium is manufactured by forming a magnetic recording layer for magnetic recording on the main surface of a disk-shaped glass substrate having a hole in the center.

A glass substrate used for manufacturing an information recording medium is referred to as an information recording medium glass substrate (hereinafter also simply referred to as a glass substrate). A method for manufacturing a glass substrate for an information recording medium is disclosed in, for example, Japanese Patent Application Laid-Open No. 2006-236561 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2007-250145 (Patent Document 2).

JP 2006-236561 A JP 2007-250145 A

With the expansion of the usage and environment of computers and the like, the impact resistance required for information recording media (magnetic disks) tends to increase year by year. When fine cracks are present on the inner and outer peripheral end faces (particularly the inner peripheral end face) of the information recording medium, the impact resistance of the information recording medium is reduced. In order to improve the impact resistance, the inner and outer peripheral end faces of the information recording medium need to be formed sufficiently smooth by polishing.

Generally, in order to obtain high smoothness, a glass substrate (glass base plate) is ground by a grinding process and then polished with a polishing slurry. From the standpoint of improving manufacturing efficiency, etc., when performing polishing on the inner peripheral end face or outer peripheral end face of the glass base plate, the glass base plate is batch-polished in a state where a plurality of glass base plates are stacked. May be processed.

When the present inventors have variations in shape (end surface shape before polishing treatment) between the end surfaces of a plurality of stacked glass base plates, unevenness occurs in the manner of contact with the end surface of the polishing brush. As a result, it was found that variation in shape occurred between the end surfaces of the plurality of glass base plates that were subjected to batch polishing.

Furthermore, the present inventors examined the cause of variation between end surfaces (end surface shape before polishing treatment) of a plurality of stacked glass base plates, and the cause was grinding the end surfaces of the glass base plates. It was found that this was caused by the end face grinding process.

Specifically, in the end surface grinding step, the end surface of the glass base plate is ground using the grinding surface of the grindstone. The shape of the end face of the glass base plate after the grinding treatment has a unique wrinkle for each grinding surface of the grindstone because the shape of the grinding face of the grindstone is transferred almost as it is to the end face of the glass base plate. When a plurality of glass base plates ground with different grindstones or different grinding surfaces are stacked, glass base plates having different end face shapes (端) are mixed in the plurality of stacked glass base plates. It will be.

Therefore, the inventors of the present invention can overlap a plurality of glass base plates that have been ground with different grindstones or different grinding surfaces, so that the shape (end surface before polishing treatment) is between the end faces of the plurality of stacked glass base plates. It was found that the variation in the shape of the end surfaces of the plurality of glass base plates that had been subjected to batch polishing was caused.

The present invention has been made in view of the above circumstances, and even when a plurality of glass base plates are subjected to a batch polishing treatment, the end faces of the plurality of glass base plates are between each other. An object of the present invention is to provide a glass substrate for an information recording medium capable of suppressing the occurrence of variation in shape and a method for manufacturing the same.

According to an aspect of the present invention, there is provided a method for manufacturing a glass substrate for an information recording medium, comprising: preparing a predetermined number of glass base plates having end faces; and using a first grindstone grinding surface. The first grinding step of grinding the end face of the glass base plate for one sheet and the second grindstone grinding surface are used to grind the end face of the glass base plate for the second number of the predetermined number. A second grinding step and a plurality of the glass base plates out of the predetermined number of the end surfaces ground, and the end surfaces of the plurality of the glass base plates in a stacked state using a polishing member. And polishing the end face. In the step of polishing the end face, the first number of glass base plates ground in the first grinding step and the second ground ground in the second grinding step. The above glass base plate for the number of sheets There in a state of being stacked plurality of the glass workpiece to not mix with each other, the end faces of the plurality of the raw material glass plate superposed thereof is polished.

According to another aspect of the present invention, there is provided a method of manufacturing a glass substrate for an information recording medium, comprising: preparing a predetermined number of glass base plates having end faces; and using a first grindstone grinding surface, Using the first grinding step of grinding the end face of the glass base plate for the first number of sheets and the second grinding wheel grinding surface, the end face of the glass base plate for the second number of the predetermined number of sheets is used. A second grinding step for grinding and a plurality of the glass base plates of the predetermined number of the ground end surfaces are stacked, and the end surfaces of the plurality of the glass base plates in a stacked state are used as a polishing member And in the step of polishing the end face, the first glass sheets ground in the first grinding step are stacked as a continuous mass, On top of that stacked multiple In the state where the end face of the glass base plate is polished and the second number of glass base plates ground in the second grinding step are stacked as a continuous lump, the plurality of stacked glass elements are stacked. The end face of the plate is polished.

Preferably, the method for manufacturing a glass substrate for an information recording medium according to the present invention further includes a step of preparing a rod-shaped positioning member, and the glass base plate is directed from one main surface to the other main surface. And the end surface is an inner peripheral end surface that forms the hole, and in the step of polishing the inner peripheral end surface, the plurality of glass base plates in the stacked state are By inserting the positioning member into the hole, the plurality of glass base plates in a stacked state are positioned, and the outer diameter of the positioning member is −0.05 mm or more with respect to the inner diameter of the hole. It is a dimension of 03 mm or less.

Preferably, the polishing member is a polishing brush having a plurality of brush bristle materials on a surface thereof, and in the step of polishing the end surface, the end surfaces of the plurality of stacked glass base plates are used for the polishing. It is ground by the brush bristle material of the brush, and the length from the root to the hair tip of the brush bristle material is within 4 mm.

Preferably, in the step of polishing the end face, a polishing slurry is poured between the polishing member and the end face.

Preferably, when the end surface of the glass base plate is ground, the first grinding wheel grinding surface and / or the second grinding wheel grinding surface are in contact with the end surface along the circumferential direction of the glass base plate. Slide.

The glass substrate for information recording medium based on the present invention is manufactured using the above-described method for manufacturing a glass substrate for information recording medium based on the present invention.

According to the present invention, even when batch polishing is performed on a plurality of glass base plates, information recording that can suppress the occurrence of variation in shape between the end faces of the plurality of glass base plates. A glass substrate for a medium and a manufacturing method thereof can be obtained.

It is a perspective view which shows an information recording device provided with the glass substrate manufactured by using the manufacturing method of the glass substrate for information recording media in embodiment. It is a top view which shows the glass substrate manufactured by the manufacturing method of the glass substrate for information recording media in embodiment. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. It is a top view which shows the information recording medium provided with the glass substrate manufactured by the manufacturing method of the glass substrate for information recording media in embodiment. FIG. 5 is a cross-sectional view taken along line VV in FIG. 4. It is a flowchart which shows the manufacturing method of the glass substrate for information recording media in embodiment. It is sectional drawing which shows a mode that the grinding process (inner peripheral end surface side) of the manufacturing method of the glass substrate for information recording media in embodiment is performed. It is sectional drawing which shows a mode that the grinding process (periphery end surface side) of the manufacturing method of the glass substrate for information recording media in embodiment is performed. It is a perspective view which shows the fixing jig and positioning tool used for the end surface grinding | polishing process of the manufacturing method of the glass substrate for information recording media in embodiment. It is sectional drawing which shows the state in which the positioning tool was inserted from opening of the fixing jig in the end surface grinding | polishing process of the manufacturing method of the glass substrate for information recording media in embodiment. It is sectional drawing which shows the state by which the positioning tool was extracted from the opening of the fixing jig in the end surface grinding | polishing process of the manufacturing method of the glass substrate for information recording media in embodiment. It is a perspective view which shows the brush for grinding | polishing used for the end surface grinding | polishing process of the manufacturing method of the glass substrate for information recording media in embodiment. It is sectional drawing which shows the state by which the brush for grinding | polishing was arrange | positioned inside the hole of a glass base plate in the end surface grinding | polishing process of the manufacturing method of the glass substrate for information recording media in embodiment. It is a figure which expands and shows the grindstone used for the end surface grinding process of the manufacturing method of the glass substrate for information recording media in embodiment. It is sectional drawing which shows a mode that the glass base plate from which end surface shape differs is mixed in a block body. It is sectional drawing (the 1) which shows a mode that the glass base plate from which end surface shape differs is not mixed in a block body. It is sectional drawing (the 2) which shows a mode that the glass base plate from which end surface shape differs is not mixed in a block body. It is sectional drawing which shows a mode when polishing slurry is poured between the brush for grinding | polishing and the internal peripheral end surface of a glass base plate in the end surface grinding | polishing process of the manufacturing method of the glass substrate for information recording media in embodiment. It is a figure which shows the conditions and result of the Example and comparative example regarding embodiment.

Embodiments and examples based on the present invention will be described below with reference to the drawings. In the description of the embodiments and the examples, when the number, amount, and the like are referred to, the scope of the present invention is not necessarily limited to the number, amount, and the like unless otherwise specified. In the description of the embodiment and each example, the same parts and corresponding parts are denoted by the same reference numerals, and redundant description may not be repeated.

[Embodiment]
(Information recording device 30)
First, the information recording device 30 will be described with reference to FIG. FIG. 1 is a perspective view showing the information recording apparatus 30. The information recording apparatus 30 includes the glass substrate 1 manufactured by the method for manufacturing a glass substrate for information recording medium (hereinafter also simply referred to as a glass substrate) in the embodiment as the information recording medium 10.

Specifically, the information recording device 30 includes an information recording medium 10, a housing 20, a head slider 21, a suspension 22, an arm 23, a vertical shaft 24, a voice coil 25, a voice coil motor 26, a clamp member 27, and a fixing screw. 28. A spindle motor (not shown) is installed on the upper surface of the housing 20.

An information recording medium 10 such as a magnetic disk is rotatably fixed to the spindle motor by a clamp member 27 and a fixing screw 28. The information recording medium 10 is rotationally driven by this spindle motor at, for example, several thousand rpm. Although details will be described later with reference to FIGS. 4 and 5, in the information recording medium 10, a chemically strengthened layer 12 (see FIG. 5) and a magnetic recording layer 14 (see FIGS. 4 and 5) are formed on the glass substrate 1. To be manufactured.

The arm 23 is attached so as to be swingable around the vertical axis 24. A suspension 22 formed in a leaf spring (cantilever) shape is attached to the tip of the arm 23. A head slider 21 is attached to the tip of the suspension 22 so as to sandwich the information recording medium 10.

A voice coil 25 is attached to the opposite side of the arm 23 from the head slider 21. The voice coil 25 is clamped by a magnet (not shown) provided on the housing 20. A voice coil motor 26 is constituted by the voice coil 25 and the magnet.

A predetermined current is supplied to the voice coil 25. The arm 23 swings around the vertical axis 24 by the action of electromagnetic force generated by the current flowing through the voice coil 25 and the magnetic field of the magnet. As the arm 23 swings, the suspension 22 and the head slider 21 also swing in the direction of the arrow AR1. The head slider 21 reciprocates on the front and back surfaces of the information recording medium 10 in the radial direction of the information recording medium 10. A magnetic head (not shown) provided on the head slider 21 performs a seek operation.

While the seek operation is performed, the head slider 21 receives a levitation force due to the air flow generated as the information recording medium 10 rotates. Due to the balance between the levitation force and the elastic force (pressing force) of the suspension 22, the head slider 21 travels with a constant flying height with respect to the surface of the information recording medium 10. By the traveling, the magnetic head provided on the head slider 21 can record and reproduce information (data) on a predetermined track in the information recording medium 10. The information recording apparatus 30 on which the glass substrate 1 is mounted as a part of the members constituting the information recording medium 10 is configured as described above.

(Glass substrate 1)
FIG. 2 is a plan view showing glass substrate 1 manufactured by the method for manufacturing a glass substrate for information recording medium according to the present embodiment. 3 is a cross-sectional view taken along the line III-III in FIG.

As shown in FIGS. 2 and 3, the glass substrate 1 (glass substrate for information recording medium) used as a part of the information recording medium 10 (see FIGS. 4 and 5) has a main surface 2, a main surface 3, It has the inner peripheral end surface 4, the hole 5, and the outer peripheral end surface 6, and is formed in a disk shape as a whole. The hole 5 is provided so as to penetrate from one main surface 2 toward the other main surface 3. A chamfer 7 is formed between the main surface 2 and the inner peripheral end surface 4 and between the main surface 3 and the inner peripheral end surface 4. Between the main surface 2 and the outer peripheral end surface 6 and between the main surface 3 and the outer peripheral end surface 6, a chamfered portion 8 (chamfer portion) is formed.

The size of the glass substrate 1 is, for example, 0.8 inch, 1.0 inch, 1.8 inch, 2.5 inch, or 3.5 inch. The thickness of the glass substrate is, for example, 0.30 mm to 2.2 mm from the viewpoint of preventing breakage. In the present embodiment, the 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. The thickness of the glass substrate is a value calculated by averaging the values measured at a plurality of arbitrary points to be pointed on the glass substrate.

(Information recording medium 10)
FIG. 4 is a plan view showing an information recording medium 10 provided with a glass substrate 1 as an information recording medium. FIG. 5 is a cross-sectional view taken along the line VV in FIG.

4 and 5, the information recording medium 10 includes a glass substrate 1, a chemical strengthening layer 12, and a magnetic recording layer 14. Chemical strengthening layer 12 is formed to cover

main surfaces

2 and 3, inner peripheral end surface 4, and outer peripheral end surface 6 of glass substrate 1. The magnetic recording layer 14 is formed so as to cover a predetermined region on the

main surfaces

2 and 3 of the chemical strengthening layer 12. By forming the chemical strengthening layer 12 on the inner peripheral end face 4 of the glass substrate 1, a hole 15 is formed inside the inner peripheral end face 4. The information recording medium 10 is fixed to a spindle motor provided on the housing 20 (see FIG. 1) using the holes 15.

In the information recording medium 10 shown in FIG. 5, the magnetic recording layer 14 is formed on both (both sides) the chemical strengthening layer 12 formed on the main surface 2 and the chemical strengthening layer 12 formed on the main surface 3. Is formed. The magnetic recording layer 14 may be provided only on the chemical strengthening layer 12 (one side) formed on the main surface 2, or on the chemical strengthening layer 12 (one side) formed on the main surface 3. It may be provided.

The magnetic recording layer 14 is formed by spin-coating a thermosetting resin in which magnetic particles are dispersed on the chemical strengthening layer 12 on the

main surfaces

2 and 3 of the glass substrate 1 (spin coating method). The magnetic recording layer 14 may be formed by a sputtering method or an electroless plating method performed on the chemical strengthening layer 12 on the

main surfaces

2 and 3 of the glass substrate 1.

The thickness of the magnetic recording layer 14 is about 0.3 μm to 1.2 μm for the spin coating method, about 0.04 μm to 0.08 μm for the sputtering method, and about 0.05 μm to about the electroless plating method. 0.1 μm. From the viewpoint of thinning and high density, the magnetic recording layer 14 is preferably formed by sputtering or electroless plating.

As a magnetic material used for the magnetic recording layer 14, a Co-based alloy or the like containing Ni or Cr as a main component is added for the purpose of adjusting the residual magnetic flux density. Is preferably used.

In order to improve the sliding of the magnetic head, the surface of the magnetic recording layer 14 may be thinly coated with a lubricant. Examples of the lubricant include those obtained by diluting perfluoropolyether (PFPE), which is a liquid lubricant, with a solvent such as Freon.

The magnetic recording layer 14 may be provided with a base layer or a protective layer as necessary. The underlayer in the information recording medium 10 is selected according to the type of magnetic film. Examples of the material for the underlayer include at least one material selected from nonmagnetic metals such as Cr, Mo, Ta, Ti, W, V, B, Al, and Ni.

The underlayer provided on the magnetic recording layer 14 is not limited to a single layer, and may have a multilayer structure in which the same or different layers are stacked. For example, a multilayer underlayer such as Cr / Cr, Cr / CrMo, Cr / CrV, NiAl / Cr, NiAl / CrMo, or NiAl / CrV may be used.

Examples of the protective layer for preventing wear and corrosion of the magnetic recording layer 14 include a Cr layer, a Cr alloy layer, a carbon layer, a hydrogenated carbon layer, a zirconia layer, and a silica layer. These protective layers can be formed continuously with an in-line type sputtering apparatus together with the underlayer and the magnetic film. These protective layers may be a single layer, or may have a multilayer structure composed of the same or different layers.

Another protective layer may be formed on the protective layer or instead of the protective layer. For example, in place of the protective layer, tetraalkoxylane is diluted with an alcohol-based solvent on a Cr layer, and then colloidal silica fine particles are dispersed and applied, followed by baking to form a silicon oxide (SiO ₂ ) layer. It may be formed.

(Glass substrate manufacturing method)
Next, the manufacturing method (S100) of the glass substrate (glass substrate for information recording media) in this Embodiment is demonstrated using the flowchart figure shown in FIG. The glass substrate manufacturing method (S100) in the present embodiment includes a glass base plate preparation step (S10), an alumina polishing step (S20), a coring step (S30), an end surface grinding step (S40), and an end surface polishing step ( S50), a lapping process (S60), a polishing process (S70), and a chemical strengthening process (S80).

A magnetic recording layer deposition step (S200) is performed on the glass substrate obtained through the chemical strengthening step (S80). The information recording medium 10 (see FIGS. 4 and 5) is obtained through the magnetic recording layer deposition step (S200). Hereinafter, the details of the steps S10 to S80 constituting the glass substrate manufacturing method (S100) will be described in order. In the following description, the simple cleaning appropriately performed between the steps S10 to S80 will be described in detail. It may not be listed.

(S10: Glass base plate preparation process)
First, a predetermined number of substantially disk-shaped glass base plates constituting the glass substrate are prepared. The glass base plate can be obtained, for example, by directly pressing molten glass using an upper mold, a lower mold, and a body mold. At this time, instead of the direct press method, a disk-shaped glass base plate may be obtained by cutting out with a grinding wheel from a sheet glass formed by using a downdraw method or a float method.

(S20: Alumina polishing step)
Next, alumina polishing is performed on a predetermined number of glass base plates. The purpose of this alumina polishing treatment is to improve dimensional accuracy and shape accuracy. The alumina polishing process is performed using a lapping apparatus. By using alumina abrasive grains of particle size # 400, setting the load to about 100 kg and rotating the inner and outer rotation gears, both main surfaces of the glass base plate housed in the carrier are polished.

(S30: Coring process)
Next, using a cylindrical grindstone, holes are respectively formed in the central portions of a predetermined number of glass base plates. This hole corresponds to the hole 5 in FIGS. 2 and 3, and is used when the information recording medium 10 is fixed to the spindle motor.

(S40: End grinding process)
In the end surface grinding step (S40), the inner peripheral end surface and the outer peripheral end surface of the predetermined number of glass base plates are ground, respectively, and a predetermined chamfering process is performed on the inner peripheral end surface and the outer peripheral end surface. The end surface grinding step (S40) in the present embodiment includes a first grinding step (S41) and a second grinding step (S42).

Referring to FIG. 7, when a grinding process is performed on the inner peripheral end face 4 of a predetermined number of glass base plates 1 (glass substrate), a grinding wheel 40 is used. The grinding wheel 40 includes grinding surfaces 41 to 46 and is rotatably supported by

support portions

47 and 48. The grinding surface 41 is brought into contact with the inner peripheral end surface 4 of the glass base plate 1 while the grinding wheel 40 receives driving force and rotates in the direction of the arrow AR40. The inner peripheral end surface 4 of the glass base plate 1 has a chamfered portion 7 by sliding in the circumferential direction of the glass base plate 1 with the grinding surface 41 in contact with the inner peripheral end surface 4 of the glass base plate 1. It is ground to the shape.

(First grinding step S41)
In the end surface grinding step (S40) of the present embodiment, the inner circumference of the glass base plate 1 corresponding to the first number (for example, 2000) of the predetermined number (for example, 10,000) prepared in the above-described steps. A grinding process is performed on the end surface 4 using a grinding surface 41 (first grinding wheel grinding surface). The service life of the grinding surface 41 expires by the grinding process for the first number of sheets. The step of grinding the inner peripheral end face of the first number of glass base plates out of a predetermined number using the grinding surface 41 (first grindstone grinding face) is the first grinding step (S41) (inner peripheral end face 4). Corresponds to the grinding step).

(Second grinding step S42)
Thereafter, a grinding process is performed on the inner peripheral end face 4 of the second number of glass sheets (for example, another 2000) of the predetermined number of sheets using the grinding surface 42 (second grinding wheel grinding surface). The The service life of the grinding surface 42 expires by the second number of grinding processes. The step of grinding the inner peripheral end surface of the second number of glass base plates out of a predetermined number using the grinding surface 42 (second grindstone grinding surface) is the second grinding step (S42) (inner peripheral end surface 4). Corresponds to the other grinding step). In addition, as the 2nd grindstone grinding surface of this invention, you may form in the grindstone 40 for grinding same as the grinding surface 41, or other grinding different from the grinding grindstone 40 in which the grinding surface 41 is formed. It may be formed on a grinding wheel for use.

Thereafter, a necessary number of grinding processes are sequentially performed on the inner peripheral end face 4 of the glass base plate 1 using the grinding surfaces 43 to 46.

Referring to FIG. 8, similarly, when grinding processing is performed on the outer peripheral end surface 6 of a predetermined number of glass base plates 1 (glass substrate), a grinding wheel 50 is used. The grinding wheel 50 includes grinding surfaces 51 to 56, and is rotatably supported by

support portions

57 and 58. The grinding surface 51 is brought into contact with the outer peripheral end surface 6 of the glass base plate 1 while the grinding wheel 50 receives driving force and rotates in the direction of the arrow AR50. The outer peripheral end surface 6 of the glass base plate 1 has a predetermined shape having a chamfered portion 8 by sliding in the circumferential direction of the glass base plate 1 in a state where the ground surface 51 is in contact with the outer peripheral end surface 6 of the glass base plate 1. To be ground.

(First grinding step S41)
In the end surface grinding step (S40) of the present embodiment, the outer peripheral end surface of the glass base plate 1 of the first number (for example, 2000) of the predetermined number (for example, 10,000) prepared in the above-described steps. 6 is ground using a grinding surface 51 (first grinding wheel grinding surface). The service life of the grinding surface 51 expires by the grinding process for the first number of sheets. The step of grinding the inner peripheral end surface of the first number of glass base plates out of a predetermined number using the grinding surface 51 (first grindstone grinding surface) is the first grinding step (S41) (of the outer peripheral end surface 6). This corresponds to the grinding process. As 1st grinding process S41, the inner peripheral end surface 4 and the outer peripheral end surface 6 may be ground simultaneously, and the inner peripheral end surface 4 and the outer peripheral end surface 6 may be ground separately.

(Second grinding step S42)
Thereafter, a grinding process is performed using the grinding surface 52 (second grinding wheel grinding surface) on the outer peripheral end face 6 of the second number of glass sheets (for example, another 2000) of the predetermined number of sheets. The service life of the grinding surface 52 is expired by the second number of grinding processes. The step of grinding the outer peripheral end surface of the second number of glass substrates out of the predetermined number using the grinding surface 52 (second grinding wheel grinding surface) is the second grinding step (S42) (other than the outer peripheral end surface 6). Corresponds to the grinding step).

Thereafter, a necessary number of grinding processes are sequentially performed on the outer peripheral end face 6 of the glass base plate 1 using the grinding surfaces 53 to 56.

(S50: End face polishing step)
Next, an end surface polishing step (S50) using a polishing slurry such as cerium oxide is performed. The end surface polishing step (S50) includes an inner peripheral end surface polishing step (S51) and an outer peripheral end surface polishing step (S52).

Referring to FIG. 9, in the inner peripheral end surface polishing step (S51) and the outer peripheral end surface polishing step (S52), fixing jig 60 and positioning tool 70 prepared separately from the above steps are used. . The fixing jig 60 includes a lid member 61 and a pedestal 64. The lid member 61 has one opening 62 in the center and four openings 63 in the vicinity of the periphery. The pedestal 64 has one opening 65 in the center and a support member 66 on the surface in the vicinity of the periphery. The positions of the four support members 66 correspond to the positions of the four openings 63 provided in the lid member 61, and the four support members 66 are inserted into the four openings 63, respectively. 64 are fixed to each other.

The positioning tool 70 includes a pedestal 71 and a rod-shaped portion 72 (bar-shaped positioning member). The rod-like portion 72 is formed in a columnar shape, and is provided so as to stand perpendicularly to the surface of the pedestal 71 at the center of the pedestal 71.

As shown in FIG. 9, the glass base plate 1 on which the inner peripheral end face 4 and the outer peripheral end face 6 have been ground is placed in a block shape (block body 9), for example, in a state where 400 pieces are stacked. 60 is accommodated inside four support members 66 (see arrow AR9). The glass base plates 1 may be sequentially accommodated one by one so as to be laminated inside the four support members 66 of the fixing jig 60. After the plurality of glass base plates 1 are arranged inside the fixing jig 60, the positioning tool 70 is inserted from the opening 65.

FIG. 10 is a cross-sectional view showing a state in which the positioning tool 70 is inserted from the opening 65. The plurality of glass base plates 1 are positioned (aligned) so as to be aligned on substantially the same straight line by the contact between the inner peripheral end face 4 and the rod-shaped portion 72. At this time, the outer diameter D72 of the rod-like portion 72 (positioning member) is preferably a dimension of −0.05 mm or more and −0.03 mm or less with respect to the inner diameter D4 of the hole 5.

For example, 400 glass base plates 1 are fixed between the lid member 61 and the pedestal 64 as the block body 9 while being positioned by the positioning tool 70. A spacer or the like may be provided between the adjacent glass base plates 1. After the plurality of glass base plates 1 are positioned and sandwiched and fixed, the positioning tool 70 is pulled out from the fixing jig 60 (see FIG. 11).

As shown in FIG. 11, when the plurality of glass base plates 1 are clamped and fixed using the fixing jig 60, the outer diameter D72 of the rod-like portion 72 (positioning member) is −0. With the dimensions of 05 mm or more and −0.03 mm or less, the plurality of glass base plates 1 can be positioned with high accuracy.

Referring to FIG. 12, a polishing brush 80 (abrasive member) is used when the polishing process is performed on the inner peripheral end surface 4 and the outer peripheral end surface 6 of the plurality of glass base plates 1. The polishing brush 80 includes a plurality of brush bristle materials 81 and a shaft portion 82. The brush bristle material 81 provided on the surface of the polishing brush 80 is disposed so as to surround the shaft portion 82 in a spiral shape.

Referring to FIG. 13, the length W81 from the root to the tip of the brush bristle material 81 of the polishing brush 80 used for the polishing process (especially the polishing process of the inner peripheral end face 4) is preferably 4 mm or less.

Referring to FIG. 14, here, the grinding surface 41 and the grinding surface 42 of the grinding wheel 40 used in the first grinding step S41 of the end surface grinding step (S40) are slightly different from each other due to the influence of manufacturing errors and the like. Have different shapes. It is difficult to completely eliminate this manufacturing error, and the same applies to the grinding surfaces 43 to 46 shown in FIG. The same applies to the grinding surfaces 51 to 56 shown in FIG.

As shown in FIG. 14, for example, the chamfering grinding surface 41 a of the grinding surface 41 and the chamfering grinding surface 42 a of the grinding surface 42 are formed to have the same shape. Even in this case, the chamfering grinding surface 41 c of the grinding surface 41 may be formed longer than the chamfering grinding surface 42 c of the grinding surface 42. Further, the grinding surface 41b for end surface processing in the grinding surface 41 may be formed to be inclined as compared with the grinding surface 42b for end surface processing in the grinding surface 42.

Referring to FIG. 15, the glass base plate 1 </ b> A ground using the grinding surface 41 of the grinding wheel 40 and the grinding surface 42 of the grinding wheel 40 in the block body 9 (see FIG. 9). It is assumed that the glass base plate 1B ground by use is mixed. In this case, even if the polishing brush 80 is rotated in the direction of the arrow AR80 and the inner peripheral end face 4 of each of the

glass base plates

1A and 1B is subjected to the polishing process, the polishing brush 80 hits the inner peripheral end face 4. As a result, unevenness occurs, and as a result, variations in shape occur between the inner peripheral end faces 4 of the plurality of

glass base plates

1A and 1B that have been subjected to batch polishing. The same applies to the outer peripheral end faces 6 of the plurality of

glass base plates

1A and 1B.

Referring to FIG. 16, in the method for manufacturing a glass substrate in the present embodiment, a plurality of glass base plates of a predetermined number of the inner peripheral end face 4 that have been ground are stacked and a plurality of the stacked base plates are stacked. When the inner peripheral end surface 4 of the glass base plate is polished using the polishing brush 80, the first number of glass base plates 1A ground in the first grinding step (S41) and the second grinding step (S42) In a state where a plurality of glass base plates 1A or a plurality of glass base plates 1B are stacked so that the second number of ground glass base plates 1B are not mixed with each other, the plurality of stacked glass base plates 1A Alternatively, the inner peripheral end surfaces 4 of the plurality of glass base plates 1B are polished. In the state where the first number of glass base plates 1A ground in the first grinding step (S41) are stacked as a continuous lump, the end surfaces of the plurality of stacked glass base plates 1A are polished. In a state where the second number of glass base plates 1B ground in the second grinding step (S42) are stacked as a continuous lump, the end surfaces of the stacked glass base plates 1B are polished.

As shown in FIG. 16, a polishing brush 80 (brush hairs) is obtained by performing a polishing process by stacking only a plurality of glass base plates 1A out of the first number of sheets ground in the first grinding step (S41). The occurrence of unevenness in how the material 81) hits the inner peripheral end face 4 is suppressed, and as a result, variations in shape occur between the inner peripheral end faces 4 of the plurality of glass base plates 1A subjected to batch polishing. This is also suppressed.

Referring to FIG. 17, similarly for glass base plate 1 </ b> B, a polishing process is performed by stacking only a plurality of glass base plates 1 </ b> B out of the second number of sheets ground in the second grinding step (S <b> 42). Thus, the occurrence of unevenness in the manner in which the polishing brush 80 (brush bristle material 81) hits the inner peripheral end surface 4 is suppressed, and as a result, the inner peripheral end surfaces 4 of the plurality of glass base plates 1B subjected to batch polishing processing. It is also possible to suppress the variation in shape between them.

Referring to FIG. 18, in the end surface polishing step (S50), the polishing process may be performed in a state in which block body 9 (see FIG. 9) and polishing brush 80 are completely immersed in the polishing liquid. However, as shown in FIG. 18, the polishing process may be performed while the polishing slurry is poured (spread) between the inner peripheral end surface 4 and the polishing brush 80.

In this case, the block body 9 and the polishing brush 80 are accommodated in a region surrounded in a liquid-tight manner by the cylindrical side wall 91, the bottom plate 93, and the lid member 92. The polishing treatment is performed while polishing slurry is poured from the opening 95 provided in the center of the lid member 92 using the nozzle 90.

Referring to FIG. 6 again, in the end surface polishing step (S50) in the present embodiment, both the glass base plate 1A and the glass base plate in both the inner peripheral end surface polishing step (S51) and the outer peripheral end surface polishing step (S52), respectively. The polishing process is performed batchwise so that the plates 1B are not confused. Note that as the end surface polishing step (S50) in the present embodiment, only the inner peripheral end surface polishing step (S51) is performed in a batch manner so that the glass base plate 1A and the glass base plate 1B are not confused with each other. Alternatively, only in the outer peripheral end surface polishing step (S52), the polishing process may be performed batchwise so that the glass base plate 1A and the glass base plate 1B are not confused with each other.

(S60: Lapping process)
After the glass base plate 1 (

glass base plates

1A and 1B) that has undergone the end surface polishing step (S50) is washed, lapping is performed. After changing the grain size of the abrasive grains to a finer one, lapping using a lapping device is performed on the

main surfaces

2 and 3 of the glass base plate 1.

(S70: Polishing process)
Polishing is performed after washing | cleaning the glass base plate 1 (

glass base plate

1A, 1B) which passed through the lapping process (S60). Polishing is performed on the

main surfaces

2 and 3 of the glass base plate 1 using a polishing apparatus (hard and soft polishing pads).

(S80: Chemical strengthening process)
Next, a chemical strengthening process is implemented to the glass base plate 1 (

glass base plate

1A, 1B) which finished the washing | cleaning process. A chemical strengthening treatment tank is prepared, and a chemical strengthening liquid in which potassium nitrate (60%) and sodium nitrate (40%) are mixed is stored therein. The chemical strengthening liquid is heated to 300 ° C. to 400 ° C. and the cleaned glass base plate 1 is preheated to 200 ° C. to 300 ° C.

The glass base plate 1 is immersed in the chemical strengthening solution for 3 to 4 hours. Since the entire surface of the glass base plate 1 is chemically strengthened during the immersion, the plurality of glass base plates 1 are accommodated in a holder or the like so that the plurality of glass base plates 1 are held by the respective end faces. It is preferable to be immersed in a state.

The alkali metal ions such as lithium ions and sodium ions contained in the glass base plate 1 are replaced by alkali metal ions such as potassium ions having a larger ion radius than these ions (ion exchange method). Compressive stress is generated in the ion-exchanged region due to the strain caused by the difference in ion radius, and both main surfaces of the glass base plate are strengthened.

After the above steps are completed, the glass base plate 1 is ultrasonically cleaned using a high frequency of 950 kHz, or cleaned using an alkaline detergent so that the adhered matter remaining on the glass base plate 1 is eliminated. To do. Thereafter, the glass base plate 1 is dried using IPA vapor. Thus, the glass substrate in the present embodiment is obtained.

Information recording such as a magnetic disk manufactured using the glass substrate 1 (see FIGS. 2 and 3) by removing the deposits remaining on the main surface of the glass substrate 1 after the chemical strengthening process. The occurrence of head crashes in the medium 10 (see FIGS. 4 and 5) is reduced. The glass substrate manufacturing method (S100) in the present embodiment is configured as described above.

(S200: Magnetic thin film formation process)
Magnetic recording layers are formed on both main surfaces (or one of the main surfaces) of the glass substrate that has been subjected to the chemical strengthening treatment. The magnetic recording layer includes, for example, an adhesion layer made of a Cr alloy, a soft magnetic layer made of a CoFeZr alloy, an orientation control underlayer made of Ru, a perpendicular magnetic recording layer made of a CoCrPt alloy, a protective layer made of a C system, and an F system. Are formed by sequentially forming the lubricating layer. By forming the magnetic recording layer, the information recording medium 10 shown in FIGS. 4 and 5 can be obtained.

(Action / Effect)
As described above, in the glass substrate manufacturing method according to the present embodiment, the inner peripheral end surfaces 4 of the predetermined number of

glass base plates

1A and 1B whose inner peripheral end surfaces 4 are ground are polished using the polishing brush 80. In doing so, the first number of glass base plates 1A ground in the first grinding step (S41) and the second number of glass base plates 1B ground in the second grinding step (S42) are not mixed with each other. Thus, the inner peripheral end surface 4 of the laminated | stacked several glass base plate is grind | polished in the state with which the several glass base plate was piled up.

According to the said structure, it is suppressed that a nonuniformity arises in the contact method with respect to the internal peripheral end surface 4 of the brush 80 for polishing (brush bristle material 81), and, as a result, of the some glass base plate 1 grind | polished by batch Variations in shape between the inner peripheral end faces 4 are also suppressed. As a result, since the glass base plate 1 having high smoothness can be obtained on the inner peripheral end face 4, it is possible to improve the impact resistance as the glass base plate 1. The same applies to the outer peripheral end face 6.

Further, when the length W81 from the root to the tip of the brush bristle material 81 of the polishing brush 80 used for the polishing process (especially the polishing process of the inner peripheral end face 4) is within 4 mm, the end face of the glass base plate 1 On the other hand, when the brush bristle material 81 of the polishing brush 80 abuts, the pressure distribution received by the end face of the glass base plate 1 is easily affected by the unevenness of the end face. Therefore, by overlapping and polishing the glass base plate 1A and the glass base plate 1B so that they are not mixed with each other, the influence of the end surface irregularities is suppressed, and the brush bristle material 81 of the polishing brush 80 Even if the length W81 from the root to the hair tip is within 4 mm, the glass base plate 1 having high smoothness can be obtained.

Further, when the polishing process is performed while the polishing slurry is poured between the inner peripheral end surface 4 and the polishing brush 80, the sludge (polishing waste) is discharged as compared with a device that is completely immersed in the polishing liquid. The capacity is lowered and the processing rate is also lowered. On the other hand, by laminating and polishing the glass base plate 1A and the glass base plate 1B so that they are not mixed with each other, the processing rate is improved even with a flow-through type polishing apparatus, and the polishing amount The non-uniformity is eliminated and the yield rate is improved.

Also, in the grinding process of the present embodiment, the ground surface slides in the circumferential direction of the glass base plate 1 with the ground surface in contact with the end face of the glass base plate 1. Since the end surface of the glass base plate 1 is ground only in the circumferential direction, the processing apparatus can be simplified.

[Experimental example]
Referring to FIG. 19, as an example, an experiment was conducted on Examples 1 to 4 based on the above-described embodiment and Comparative Examples 1 to 4 for these. In Examples 1 to 4 and Comparative Examples 1 to 4, the glass base plate preparation process, the alumina polishing process for ensuring flatness, and the coring process are the same conditions as in the above-described embodiment. In the end surface grinding process, in Examples 1 to 4, a plurality of glass base plates 1 are ground using the same grinding surface with the same grindstone, and in Comparative Examples 1 to 4, the same grindstone is used. The grinding process was implemented with respect to the several glass base plate 1 using the grinding surface by a different grinding surface or a different grindstone.

In the inner peripheral end face polishing step, as shown in FIG. 19, it is assumed that the glass base plate is not mixed in Examples 1 to 4, and in Comparative Examples 1 to 4, the inner peripheral end face 4 polished by a different polishing face is used. The glass base plate 1 to be mixed was mixed. In the outer peripheral end face polishing, brush polishing was used and cerium oxide was used. As polishing conditions for the inner peripheral end face, 400 block bodies 9 were processed at one time, the rotation speed of the polishing brush 80 was set to 4000 rpm, and the rotation speed of the block body 9 was set to 30 rpm. The inner diameter of the hole 5 of the glass base plate 1 is 20.01 mm, and the polishing time is 20 min.

In lapping, grinding was performed with a double-side polishing machine and diamond sheet fixed abrasive grains in common with Examples 1 to 4 and Comparative Examples 1 to 4. In the polishing process, in common with Examples 1 to 4 and Comparative Examples 1 to 4, as the first polishing process (P1), ceria abrasive grains and hard urethane pads are used, and the second polishing process (P2 ), Colloidal silica abrasive grains and hard suede pads were used. Thereafter, the obtained glass base plate 1 was chemically strengthened to obtain a glass substrate.

Example 1
In Example 1, the block body 9 was configured so that the glass base plate 1 was not mixed, and the block body 9 was subjected to polishing treatment as described above. The dimension (outer dimension) of the rod-like portion 72 (positioning member) used as the positioning tool 70 with respect to the inner diameter of the hole 5 of the glass base plate 1 is −0.07 mm. The length of the brush bristle 81 of the polishing brush 80 is 5 mm. At the time of polishing, as shown in FIG. 18 described above, the polishing slurry was flowed between the inner peripheral end face 4 and the polishing brush 80.

(Example 2)
In Example 2, the block body 9 was configured so that the glass base plate 1 was not mixed, and the block body 9 was subjected to polishing treatment as described above. The dimension (outer dimension) of the rod-like portion 72 (positioning member) used as the positioning tool 70 with respect to the inner diameter of the hole 5 of the glass base plate 1 is −0.07 mm. The length of the brush bristle material 81 of the polishing brush 80 is 4 mm. At the time of polishing, as shown in FIG. 18 described above, the polishing slurry was flowed between the inner peripheral end face 4 and the polishing brush 80.

(Example 3)
In Example 3, the block body 9 was configured so that the glass base plate 1 was not mixed, and the block body 9 was subjected to polishing treatment as described above. The dimension (outer dimension) of the rod-like portion 72 (positioning member) used as the positioning tool 70 with respect to the inner diameter of the hole 5 of the glass base plate 1 is −0.05 mm. The length of the brush bristle 81 of the polishing brush 80 is 5 mm. At the time of polishing, as shown in FIG. 18 described above, the polishing slurry was flowed between the inner peripheral end face 4 and the polishing brush 80.

(Example 4)
In Example 4, the block body 9 was configured so that the glass base plate 1 was not mixed, and the block body 9 was subjected to polishing treatment as described above. The dimension (outer dimension) of the rod-like portion 72 (positioning member) used as the positioning tool 70 with respect to the inner diameter of the hole 5 of the glass base plate 1 is −0.05 mm. The length of the brush bristle material 81 of the polishing brush 80 is 4 mm. At the time of polishing, as shown in FIG. 18 described above, the polishing slurry was flowed between the inner peripheral end face 4 and the polishing brush 80.

(Comparative Example 1)
In the comparative example 1, the block body 9 was comprised so that the glass base plate 1 might be mixed, and the polishing process was performed with respect to the block body 9 as mentioned above. The dimension (outer dimension) of the rod-like portion 72 (positioning member) used as the positioning tool 70 with respect to the inner diameter of the hole 5 of the glass base plate 1 is −0.07 mm. The length of the brush bristle 81 of the polishing brush 80 is 5 mm. At the time of polishing, as shown in FIG. 18 described above, the polishing slurry was flowed between the inner peripheral end face 4 and the polishing brush 80.

(Comparative Example 2)
In Comparative Example 2, the block body 9 was configured so that the glass base plate 1 was mixed, and the polishing process was performed on the block body 9 as described above. The dimension (outer dimension) of the rod-like portion 72 (positioning member) used as the positioning tool 70 with respect to the inner diameter of the hole 5 of the glass base plate 1 is −0.07 mm. The length of the brush bristle material 81 of the polishing brush 80 is 4 mm. At the time of polishing, as shown in FIG. 18 described above, the polishing slurry was flowed between the inner peripheral end face 4 and the polishing brush 80.

(Comparative Example 3)
In Comparative Example 3, the block body 9 was configured so that the glass base plate 1 was mixed, and the polishing process was performed on the block body 9 as described above. The dimension (outer dimension) of the rod-like portion 72 (positioning member) used as the positioning tool 70 with respect to the inner diameter of the hole 5 of the glass base plate 1 is −0.05 mm. The length of the brush bristle 81 of the polishing brush 80 is 5 mm. At the time of polishing, as shown in FIG. 18 described above, the polishing slurry was flowed between the inner peripheral end face 4 and the polishing brush 80.

(Comparative Example 4)
In Comparative Example 4, the block body 9 was configured so that the glass base plate 1 was mixed, and the polishing process was performed on the block body 9 as described above. The dimension (outer dimension) of the rod-like portion 72 (positioning member) used as the positioning tool 70 with respect to the inner diameter of the hole 5 of the glass base plate 1 is −0.05 mm. The length of the brush bristle material 81 of the polishing brush 80 is 4 mm. At the time of polishing, as shown in FIG. 18 described above, the polishing slurry was flowed between the inner peripheral end face 4 and the polishing brush 80.

The inner peripheral end face 4 was inspected for the glass base plates 1 obtained in Examples 1 to 4 and Comparative Examples 1 to 4. As an inspection method, the inner peripheral end surface 4 is measured for roughness using AFM (Dimension 3100 manufactured by Beco Co., Ltd. and measurement software NanoScope 7.2), and the glass base plate having a surface roughness Ra of 1.0 nm or more. The ratio of 1 was investigated, the case where the ratio of the corresponding glass base plate 1 was 10% or more was B evaluation, the case of less than 10% 6% or more was A evaluation, and the case of less than 6% was S evaluation.

In addition, as a destructive test, an information recording medium 10 formed by subjecting the glass base plate 1 to film formation is incorporated into an actual information recording device 30 (hard disk drive), and 40 shock resistance tests are performed for each condition. went. As an impact resistance test, an impact of 1000 G was applied to the information recording device 30 in the vertical direction, and the presence / absence state (good product rate) of the surface of the information recording medium 10 after the test was confirmed.

As shown in FIG. 19, as a result, in Examples 1 to 4, the state of the inner peripheral end face 4 was A evaluation or S evaluation, whereas in Comparative Examples 1 to 4, all were B evaluation. there were. In Comparative Examples 1 to 4, results with a large number of destruction were obtained. As a result of confirming the breaking conditions of the glass base plates 1 of Comparative Examples 1 to 4, an internal crack was generated in the vicinity of the inner peripheral end face 4 of the glass base plate 1, and traces that were estimated to be the cause of the break were confirmed. . In other words, in Comparative Examples 1 to 4, it was considered that good polishing was not performed because there was a variation between the inner peripheral end faces of the glass base plate 1 in the shape before polishing.

As for the external dimensions of the rod-like portion 72 of the positioning tool 70, a better result is obtained when -0.05 mm than the case of -0.07 mm with respect to the inner diameter of the hole 5 of the glass base plate 1. Obtained. In the case of −0.05 mm, the inner peripheral end face 4 is considered to be uniformly polished. When the outer dimension of the rod-like portion 72 is less than −0.03 mm with respect to the inner diameter of the hole 5 of the glass base plate 1, it is not inserted well into the hole 5 of the glass base plate 1, and it is somewhat difficult to use. there were.

Therefore, also from the result of the present embodiment, when the inner peripheral end surfaces 4 of the predetermined number of

glass base plates

1A and 1B with the inner peripheral end surfaces 4 ground are polished using the polishing brush 80, the first grinding step ( A plurality of glass base plates are arranged so that the first number of glass base plates 1A ground in S41) and the second number of glass base plates 1B ground in the second grinding step (S42) are not mixed with each other. When the inner peripheral end surfaces 4 of the plurality of stacked glass base plates are polished in the stacked state, unevenness occurs in the manner in which the polishing brush 80 (brush bristle material 81) contacts the inner peripheral end surface 4. As a result, it can be seen that variation in shape between the inner peripheral end faces 4 of the plurality of glass base plates 1 polished in batch is also suppressed. According to the said structure, since the glass base plate 1 which has high smoothness in the inner peripheral end surface 4 can be obtained, it turns out that the impact resistance as the glass base plate 1 can be improved.

As mentioned above, although each embodiment and each Example based on this invention were demonstrated, each embodiment and each Example disclosed this time are illustrations in all points, and are not restrictive. The technical scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Glass substrate (glass base plate), 2, 3 main surface, 4 inner peripheral end surface, 5,15 hole, 6 outer peripheral end surface, 7,8 chamfer part, 9 block body, 10 information recording medium, 12 chemical strengthening layer, 14 magnetic recording layer, 20 housing, 21 head slider, 22 suspension, 23 arm, 24 vertical axis, 25 voice coil, 26 voice coil motor, 27 clamp member, 28 fixing screw, 30 information recording device, 40, 50 for grinding Grinding wheel, 41, 42, 43, 44, 45, 46, 41a, 41b, 41c, 42a, 42b, 42c, 51, 52, 53, 54, 55, 56 grinding surface, 47, 48, 57, 58 support, 60 fixing jig, 61, 92 lid member, 62, 63, 65, 95 opening, 64, 71 pedestal, 66 support member, 70 positioning , 72 bar-like portion, 80 a polishing brush 81 brush hairs, 82 shaft portion, 90 a nozzle, 91 a sidewall, 93 a bottom plate.

Claims

Preparing a predetermined number of glass base plates having end faces;
A first grinding step of grinding the end face of the glass base plate for the first number of the predetermined number of sheets using a first grinding wheel grinding surface;
A second grinding step of grinding the end face of the glass base plate for a second number of the predetermined number of sheets using a second grinding wheel grinding surface;
A step of superposing a plurality of the glass base plates of the predetermined number of the ground end surfaces, and polishing the end surfaces of the superposed glass base plates using a polishing member; Prepared,
In the step of polishing the end surface, the first number of glass base plates ground in the first grinding step and the second number of glass base plates ground in the second grinding step include In a state where a plurality of the glass base plates are stacked so as not to be mixed with each other, the end surfaces of the stacked plurality of glass base plates are polished.
A method for producing a glass substrate for an information recording medium.
Preparing a predetermined number of glass base plates having end faces;
A first grinding step of grinding the end face of the glass base plate for the first number of the predetermined number of sheets using a first grinding wheel grinding surface;
A second grinding step of grinding the end face of the glass base plate for a second number of the predetermined number of sheets using a second grinding wheel grinding surface;
A step of superposing a plurality of the glass base plates of the predetermined number of the ground end surfaces, and polishing the end surfaces of the superposed glass base plates using a polishing member; Prepared,
In the step of polishing the end surface, the plurality of glass base plates stacked in the state where the first number of the glass base plates ground in the first grinding step are stacked as a continuous lump. The end surfaces of the plurality of glass base plates stacked in a state in which the second number of glass base plates ground in the second grinding step are stacked as a continuous lump. The end face is polished,
A method for producing a glass substrate for an information recording medium.
A step of preparing a rod-shaped positioning member;
The glass base plate is provided with a hole penetrating from one main surface toward the other main surface,
The end face is an inner peripheral end face that forms the hole,
In the step of polishing the inner peripheral end face, the plurality of glass base plates in the stacked state are positioned by inserting the positioning members into the holes of the plurality of glass base plates in the stacked state. And
The outer diameter of the positioning member is a dimension of −0.05 mm or more and −0.03 mm or less with respect to the inner diameter of the hole.
The manufacturing method of the glass substrate for information recording media of Claim 1 or 2.
The polishing member is a polishing brush having a plurality of brush bristle materials on the surface,
In the step of polishing the end surface, the end surfaces of the plurality of stacked glass base plates are polished by the brush bristle material of the polishing brush,
The length from the root of the brush bristle material to the hair tip is within 4 mm,
The manufacturing method of the glass substrate for information recording media in any one of Claim 1 to 3.
In the step of polishing the end face, a polishing slurry is poured between the polishing member and the end face.
The manufacturing method of the glass substrate for information recording media in any one of Claim 1 to 4.
When grinding the end surface of the glass base plate, the first grinding wheel grinding surface and / or the second grinding wheel grinding surface slide along the circumferential direction of the glass base plate in contact with the end surface. ,
The manufacturing method of the glass substrate for information recording media in any one of Claim 1 to 5.
It manufactured using the manufacturing method of the glass substrate for information recording media in any one of Claim 1 to 6.
Glass substrate for information recording media.