JP2002123931A - Method for polishing glass substrate for information recording medium and glass substrate for information recording medium polished by the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for polishing a glass substrate for an information recording medium by which the roughening of the outer edge face of the glass substrate is prevented in a step for lapping the recording surface and the smoothness of the outer edge face can be enhanced, and to provide a glass substrate for an information recording medium polished by the method. SOLUTION: A lapping step P3 for lapping the recording surface of a discoid glass substrate work 30 with an inner hole in the central part is carried out before a polishing step P4 for polishing the outer edge face of the work 30, a polishing step P5 for polishing the inner edge face of the work 30, a first polishing step P6 for polishing the recording surface of the work 30 and a second polishing step P6 for polishing the recording surface of the work 30.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for polishing a glass substrate for an information recording medium and a glass substrate for an information recording medium polished by the method.

[0002]

2. Description of the Related Art An information recording medium includes a magnetic disk and the like, and a glass substrate is used as a substrate for the magnetic disk. This glass substrate is suitable not only for reducing the size and thickness of the magnetic disk, but also has excellent flatness of the substrate recording surface and excellent substrate strength for high-density recording. As the glass substrate, generally, a chemically strengthened glass substrate or a crystallized glass substrate whose substrate strength is improved by chemical strengthening or crystallization is used.

[0003] Magnetic heads for reading information recorded on a magnetic disk have also changed from thin film heads to magnetoresistive heads (MR heads) and large magnetoresistive heads (GMR heads) as recording density has increased. Have been doing.

[0004] Such a glass substrate for a magnetic disk is
It is manufactured by the manufacturing method described below (for example, JP-A-11-221742).

Disk processing step First, a disk-shaped glass substrate work is prepared by cutting a glass base material made of aluminosilicate glass as a base material into a disk shape with a grinding wheel and grinding with a relatively rough diamond wheel. Lapping is performed on the recording surface of the glass substrate work in order to obtain predetermined dimensional accuracy and shape accuracy. This lapping is performed by a rotating nylon brush using an alumina abrasive having a grain size of # 400. At this time, the surface roughness (Rmax) (measured according to JIS B0601) is about 6 μm.

[0006] Then the outer peripheral edge chamfering process, by using a cylindrical grindstone with opening a round hole in the center of the glass substrate workpiece is subjected to a predetermined chamfering the outer peripheral end face and the inner peripheral end face. At this time, the surface roughness (Rmax) of the inner and outer peripheral end faces is 14 μm.

Inner Peripheral End Surface Polishing Step The inner peripheral end surface of the glass substrate work is ground with a rotating nylon brush to a grain size of # 400 with the glass substrate works superposed.
Is polished using an alumina abrasive polishing agent.

Recording surface lapping process The recording surface of the glass substrate work housed in the hole of the resin carrier that revolves around by a double-sided lapping machine is coated with a pair of cast iron platens using an alumina abrasive abrasive having a grain size of # 1000. And lapping to a surface roughness (Rmax) of about 2 μm.

Recording Surface First Polishing Step The recording surface of the glass substrate work wrapped in the recording surface lapping step is polished using a cerium oxide suspension to remove scratches and distortion remaining in the recording surface lapping step. (Hard cloth).

Recording surface second polishing step The recording surface of the glass substrate work polished in the recording surface first polishing step is further polished with a polisher (soft cloth) using a cerium oxide suspension.

As described above, in the conventional manufacturing method, the recording surface lapping step is performed after the end face chamfering step and the polishing step in each step of processing the glass substrate.

[0012]

However, if the end face chamfering step or the inner / outer peripheral end face polishing step is performed prior to the recording surface lapping step, foreign matter generated during the end face chamfering polishing adheres to the recording surface of the glass substrate. In some cases, if foreign matter adheres to the recording surface, the bias voltage in the thin film sputtering process during the production of the magnetic recording medium becomes unstable, causing a film defect of the thin film formed on the recording surface, It becomes a convex on the surface of the thin film, causing a problem that an appropriate glide height (glide height) cannot be obtained.

The cause of the adhesion of foreign substances to the recording surface of the glass substrate as described above is that the recording surface of the glass substrate is not smooth because the surface condition of the inner and outer peripheral end surfaces of the glass substrate is not smooth. When wrapped with the resin, particles of resin or glass generated by friction between the outer peripheral end surface of the glass substrate and the wall surface of the carrier and other particles trapped on the inner and outer peripheral end surfaces of the glass substrate are applied to the recording surface of the glass substrate. This is to adhere.

An object of the present invention is to provide a method for polishing a glass substrate for a magnetic recording medium, which can prevent the outer peripheral end surface of the glass substrate from being roughened in the recording surface lapping step and improve the smoothness of the outer peripheral end surface. An object of the present invention is to provide a polished glass substrate for a magnetic recording medium.

[0015]

According to a first aspect of the present invention, there is provided a polishing method for lapping a recording surface of a disk-shaped glass substrate work having an inner hole at a central portion. An information recording medium, comprising: an outer peripheral end surface polishing step of polishing an outer peripheral end surface of the work, an inner peripheral end surface polishing step of polishing an inner peripheral end surface of the work, and a recording surface polishing step of polishing a recording surface of the work. In the method for polishing a glass substrate for use, the recording surface lapping step is performed before the outer peripheral end face polishing step.

According to the polishing method of the present invention, since the recording surface lapping step is performed before the outer peripheral end surface polishing step, the outer peripheral end surface of the glass substrate is prevented from being roughened during the recording surface lapping step, and the inner and outer peripheral end surfaces are smoothed. The degree can be improved.

A polishing method according to a second aspect is characterized in that, in the polishing method according to the first aspect, the recording surface lapping step is performed before the inner peripheral end face polishing step.

A polishing method according to a third aspect is characterized in that, in the polishing method according to the first aspect, the recording surface lapping step is performed after the inner peripheral end face polishing step.

According to a fourth aspect of the present invention, in the polishing method according to any one of the first to third aspects, at least one of the outer peripheral end surface polishing step and the inner peripheral end surface polishing step is the information recording medium. A polishing process using a rotating brush in a state where the glass substrates for use are laminated one by one with a spacer interposed therebetween.

According to the polishing method of the present invention, the glass substrate for the information recording medium is polished by the rotating brush in a state where the glass substrates are laminated one by one with the spacer interposed therebetween, so that the entire area of the chamfered surface of the glass substrate work is provided. Can be polished.

According to a fifth aspect of the present invention, in the polishing method according to any one of the first to third aspects, at least one of the inner peripheral end face polishing step and the inner peripheral end face polishing step includes the step of polishing the workpiece. The method comprises the step of polishing with a rotating brush, and the brush tip of the rotating brush has a mountain shape.

According to the polishing method of the present invention, since the brush tip of the rotary brush has a mountain shape, it is possible to polish the entire chamfered surface of the glass substrate work without using a spacer.

According to a sixth aspect of the present invention, in the polishing method according to any one of the first to third aspects, at least one of the inner peripheral end face polishing step and the inner peripheral end face polishing step includes the step of polishing the workpiece. The method comprises a step of polishing with a rotating brush, wherein the rotating brush is configured such that the direction of the bristles is oriented along the chamfered surface of the glass substrate.

According to the polishing method of the sixth aspect, since the rotating brush is configured so that the direction of the brush bristles is oriented along the chamfered surface of the glass substrate, the rotating brush can be used without using spacers. All areas of the chamfer can be polished.

According to a seventh aspect of the present invention, a glass substrate for an information recording medium is polished by the method for polishing a glass substrate for an information recording medium according to any one of the first to sixth aspects.

According to the glass substrate for an information recording medium of the present invention, a glass substrate for an information recording medium having an improved inner and outer peripheral end surface smoothness can be obtained.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for polishing a glass substrate for a magnetic recording medium according to an embodiment of the present invention will be described below with reference to the drawings.

In the method for polishing a glass substrate for a magnetic recording medium according to the embodiment of the present invention, the inner and outer peripheral end faces and the recording surface of the glass substrate for a magnetic recording medium are polished by the steps shown in FIG.

FIG. 1 is a process chart for executing a method for polishing a glass substrate for a magnetic recording medium according to an embodiment of the present invention.

Disc Processing Step P1 First, a glass base plate made of aluminosilicate glass as a base material is cut with a glass cutter or an air drill, for example, to an outer diameter of 8 mm.
By cutting into a disk shape of 5mmφ x 24mmφ inner diameter and grinding with a relatively coarse diamond grindstone,
A disk-shaped glass substrate work is produced, and lapping is performed so that the recording surface of the glass substrate work has predetermined dimensional accuracy and shape accuracy. This lapping is performed by a rotating nylon brush using an abrasive abrasive. At this time, the surface roughness (Rmax) (measured according to JIS B0601) is about 6 μm.

As the aluminosilicate glass, for example, in terms of mol%, SiO ₂ is 57 to 74%, MgO is 1 to 5%, CaO is 1 to 6%, Al ₂ O ₃ is ₃ to 15%,
The LiO ₂ with 5 to 16%, chemically strengthened glass containing NaO ₂ as a main component 4 to 14 percent are used.

[0032] Then the outer peripheral edge chamfering process P2, the center portion of the glass substrate workpiece by using a cylindrical grindstone, for example, performs a predetermined chamfering the outer peripheral end face and the inner peripheral end face with drilling circular holes with a diameter of 20 mm.phi. At this time, the surface roughness (Rmax) of the inner and outer peripheral end faces is 14 μm.

Recording surface lapping step P3 This step is performed using a double-sided lapping machine shown in FIG. The lapping machine 20 shown in FIG. 2 includes a horizontal upper platen 21 made of cast iron and a horizontal lower platen 2 also made of cast iron.
2 The lapping surface of the upper platen 21 is pitch 20
The lower lapping surface of the lower platen 22 is cut into a 2.5 mm wide groove in a 30 mm pitch grid pattern. In addition, the upper surface plate 21
A rotary support shaft 23 is provided. Around the rotary support shaft 23, supply ports 24 of slurry-like alumina abrasive polishing agents are provided at equal angular intervals.

The upper stool 21 is clockwise as viewed from above (hereinafter, clockwise and counterclockwise all refer to the rotation direction as viewed from above) at 16 to 18 rpm, and the lower stool 22.
Rotates counterclockwise at 50-55 rpm.

A sun gear 25 is arranged at the center of the lower platen 22, and an internal gear 26 is arranged at the outer periphery. A carrier 2 having a planetary gear meshing with both the sun gear 25 and the internal gear 26 is provided on the lower platen 22.
7 are arranged. In the double-sided lapping machine 20, the sun gear 25 rotates counterclockwise at, for example, 15 to 22 rpm, and the internal gear 26 has, for example, 21 to 22 rpm.
When rotating counterclockwise at 29 rpm, carrier 2
7 revolves counterclockwise at, for example, 50 rpm while rotating clockwise on the lower platen 22. The carrier 27 is
It is an epoxy resin containing glass fiber, and its thickness is, for example, 0.2 to 0.6 mm smaller than the finished thickness (for example, 1 mm) of the glass substrate work. The material of the carrier 27 may be an epoxy containing aramid fiber.

FIG. 3 is an enlarged perspective view of the carrier 27 in FIG. The carrier 27 has, for example, seven holes 28 for accommodating a glass substrate work at equal angular intervals in the circumferential direction. The diameter of the hole 28 is, for example, 2.2 times smaller than the outer diameter of the glass substrate work 30 as shown in FIG.
It is set to be 5 mm larger. By setting the diameter of the hole 28 in this manner, damage to the outer peripheral end surface of the glass substrate work 30 can be reduced. The difference between the diameter of the hole 28 and the outer diameter of the glass substrate work 30 may be 1 to 2 mm. Further, a flexible inclusion such as a sponge may be attached to the wall of the carrier 27 that defines the hole 28.

By the double-sided lapping machine 20, the recording surface of the glass substrate work 30 accommodated in the carrier 27 which revolves on its own is given a particle size of # 1000 (average particle size of 9 to 10 μm).
surface roughness (Rma)
x) Lapping to about 2 μm. As a result, the thickness of the glass substrate work 30 can be reduced from a maximum of 20 μm / batch to 3 μm / batch or less at a maximum of 50 to 100 sheets per batch, and the thickness of each glass substrate work 30 can be made uniform. The flatness of the work 30 can be reduced from 15 μm to 5 μm. Here, the flatness is
This is an index indicating the degree of warpage of the glass substrate work 30, and is indicated by a value obtained by subtracting the net thickness from the maximum thickness of the warped glass substrate work 30.

The above particle size # 1000 (average particle size 9 to 10 μm)
m) of the alumina abrasive particles having a particle size of # 2000 (4-5
μm).

The glass substrate work 30 polished to a predetermined thickness using the double-sided lapping machine 20 has a recording surface of 1 mm in order to remove dirt of the alumina abrasive abrasive adhered to the recording surface. Etching is performed with a hydrofluoric acid (HF) etching solution of about 10 to 10% to 1 to 5 μm. The etchant is then rinsed by ultrasonic (US) cleaning. This process P
According to 3, it is possible to prevent foreign substances from being brought into the recording surface of the glass substrate work 30 and to prevent the recording surface from being stained.

Outer Edge Polishing Step P4 This step is performed by using an outer edge polishing machine shown in FIG. The outer peripheral end surface polishing machine 50 shown in FIG. 5 includes a pair of work shafts 51 for holding about 350 to 400 glass substrates having a thickness of about 1 mm in a stacked state, and a pair of bundles of glass substrate works 30, respectively. Contact glass substrate work 30
And a pair of rotating nylon brushes 52 for polishing the outer peripheral end surface and the chamfered surface of the bundle. The brush 52 also performs a reciprocating motion in the vertical direction. The brush bristle diameter of the brush 52 is 0.1 to
It is 0.5 mmφ, preferably 0.1 to 0.3 mmφ.

As shown in FIG. 6A, the glass substrate work 30 held on the work shaft 51 has a size of 80 mmφ × 26 mmφ × 0.3 mm for each glass substrate work.
A polypropylene spacer 31 having a thickness is inserted. Thereby, the rotating nylon brush 52 reaches all the areas of the chamfered surfaces of the pair of glass substrate works 30 spaced by the spacer 31, so that there is no uncut portion and the quality of the chamfered surface can be improved. Spacer 31
When no is used, an uncut portion 32 occurs as shown in FIG. The spacer 31 may be made of flexible foamed polyurethane, and may have a thickness of 0.4 to 0.6 mm.

As an alternative, the brush bristles of the brush 52 may be shaped like a chevron in accordance with the shape of the chamfered surface of the glass substrate work 30, or the brush 52 may be oriented such that the direction of the bristles is along the chamfered surface of the glass substrate work 30. In this configuration, the spacer 31 can be omitted.

The outer peripheral end surface polishing machine 50 grinds the outer peripheral end surface and the chamfered surface of the bundle of the glass substrate works 30 using a cerium oxide abrasive. Thereby, the smoothness of the outer peripheral end surface and the chamfered surface of the glass substrate work 30 can be improved, and the generation of cullet foreign matter can be prevented.

In this step P4, the glass substrate work 30
The smoothness of the outer peripheral end surface and the chamfered surface is improved.

Next, the spacer 31 is extracted from the bundle of the glass substrate works 30.

Inner Peripheral End Surface Polishing Step P5 This step is performed by the inner peripheral end surface polishing machine shown in FIG. The inner peripheral end surface polishing machine 70 shown in FIG. 7 includes a work holder 71 for holding about 100 glass substrate works 30 each having a thickness of about 1 mm in a stacked state, and a glass substrate work 30 inserted into a bundle. A rotating nylon brush 72 for polishing the inner peripheral end surface and the chamfered surface of the bundle of the works 30.

The inner diameter of the work holder 71 is about 85 mmφ
And the height is 120 mm. The rotating nylon brush 72 has a diameter of 25 mmφ and a length of 130 mm. Work holder 71 is clockwise at 40-60 rpm
, And the brush 72 rotates clockwise at 4500 rpm. The polishing is performed by using a cerium oxide abrasive polishing liquid.

The work holder 71 has an outer peripheral end surface polishing machine 5.
0 mm, 80 mm for each glass substrate work
The glass substrate work 30 is held in a state in which a spacer made of polypropylene having a size of φ × 35 mmφ × 0.3 mm is inserted. This allows the brush 72 to reach all areas of the chamfered surfaces of the pair of glass substrate works 30 spaced by the spacer, so that there is no uncut portion and the quality of the chamfered surface can be improved.

The inner peripheral end surface polishing machine 70 grinds the inner and outer peripheral end surfaces and the chamfered surface of the bundle of glass substrate works 30 using a cerium oxide abrasive. Thereby, the smoothness of the inner peripheral end surface and the chamfered surface of the glass substrate work 30 can be improved, and the occurrence of cullet foreign matter can be prevented.

The glass substrate work 30 having the inner peripheral end face and the chamfered surface polished using the inner peripheral end face polisher 70 is subjected to ultrasonic waves (US) to remove dirt on the inner peripheral end face and the chamfered surface. Washing is performed. By this process P5, the smoothness of the inner peripheral end surface and the chamfered surface of the glass substrate work 30 is improved.

Next, the spacer is extracted from the bundle of the glass substrate works 30.

Recording Surface First Polishing Step P6 The recording surface of the glass substrate work 30 whose inner peripheral end face has been polished in the above step P5 is subjected to cerium oxide suspension to remove the scratches and distortion remaining in the recording surface lapping step P3. Polish with a polisher (hard cloth) using the liquid.

Recording Surface Second Polishing Step P7 The recording surface of the glass substrate work polished in the first polishing step P6 is further polished with a polisher (soft cloth) using a cerium oxide suspension.

Cleaning Step P8 The glass substrate work 30 subjected to the polishing step P7 is
Ultraviolet (UV) cleaning is performed to remove stains of the cerium oxide suspension adhered to the recording surface or the like.

According to the present embodiment, the recording surface lapping process P3 is performed before the end surface polishing processes P4 and P5 and the polishing processes P6 and P7 among the glass substrate processing processes. In this case, it is possible to prevent the outer peripheral end surface of the glass substrate from being roughened, thereby improving the smoothness of the inner and outer peripheral end surfaces.

In this embodiment, the recording surface lapping step P3 is performed before the end face polishing steps P4 and P5 and the polishing steps P6 and P7. However, the inner peripheral end face polishing step P5 → the recording surface lapping step P3 → Outer edge polishing process P
4, the recording surface lapping step P3 → the recording surface first polishing step P6 → the outer peripheral end surface polishing step P4 → the inner peripheral end surface polishing step P5 → the recording surface second polishing step P7. . In short, it suffices if the recording surface lapping step P3 is performed before the outer peripheral end face grinding step P4.

[0057]

According to the polishing method of the first aspect, the recording surface lapping step is performed before the outer peripheral end face polishing step.
Roughness of the outer peripheral end surface of the glass substrate during the recording surface lapping step can be prevented, and the smoothness of the inner and outer peripheral end surfaces can be improved.

A polishing method according to a second aspect is characterized in that, in the polishing method according to the first aspect, the recording surface lapping step is performed before the inner peripheral end face polishing step.

According to the polishing method of the third aspect, since the glass substrate for the information recording medium is polished by the rotating brush in a state where the glass substrates are stacked one by one with the spacer interposed therebetween, the entire surface of the chamfered surface of the glass substrate work is polished. Can be polished.

According to the polishing method of the fourth aspect, since the tip of the rotating brush has a chevron shape, the entire area of the chamfered surface of the glass substrate work can be polished without using a spacer.

According to the polishing method of the fifth aspect, the rotating brush is configured such that the direction of the bristles is oriented along the chamfered surface of the glass substrate, so that the glass substrate work can be performed without using a spacer. All areas of the chamfered surface can be polished.

According to the glass substrate for an information recording medium according to the sixth aspect, a glass substrate for an information recording medium with improved smoothness of inner and outer peripheral end faces can be obtained.

[Brief description of the drawings]

FIG. 1 is a process chart for executing a method for polishing a glass substrate for a magnetic recording medium according to an embodiment of the present invention.

FIG. 2 is a partially cutaway perspective view of a main part of a double-sided lapping machine used in a recording surface lapping step P3 in FIG. 1;

FIG. 3 is an enlarged perspective view of a carrier 27 in FIG.

FIG. 4 is a partial explanatory view of a carrier 27 of FIG. 2;

FIG. 5 is a perspective view of a main part of an outer peripheral edge polishing machine used in an outer peripheral edge polishing step P4 in FIG. 1;

FIG. 6 is a view for explaining a state of polishing the outer peripheral chamfered surface of the glass substrate 30 in the outer peripheral edge polishing machine 50 of FIG. 5,
(A) shows the case where the spacer is inserted between the glass substrates 30, and (b) shows the case where the spacer is not inserted.

FIG. 7 is a perspective view of a main part of the inner peripheral end face polishing machine used in the inner peripheral end face polishing step P5 in FIG. 1;

[Explanation of symbols]

 Reference Signs List 20 lapping machine 21 upper surface plate 22 lower surface plate 25 sun gear 26 internal gear 27 carrier 28 hole 30 glass substrate work 50 outer peripheral end surface polishing machine 51 work shaft 52 rotating nylon brush 70 inner peripheral end surface polishing machine 71 work holder 72 rotating nylon brush

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C03C 19/00 C03C 19/00 Z

Claims (7)

[Claims] 1. A recording surface lapping step of lapping a recording surface of a disk-shaped glass substrate work having an inner hole at a center portion, an outer peripheral end surface polishing step of polishing an outer peripheral end surface of the work, and an inner peripheral end surface of the work In the method for polishing a glass substrate for an information recording medium having an inner peripheral end surface polishing step of polishing the surface and a recording surface polishing step of polishing the recording surface of the work, the recording surface lapping step is performed before the outer peripheral end surface polishing step. A method for polishing a glass substrate for an information recording medium. 2. The method for polishing a glass substrate for an information recording medium according to claim 1, wherein the recording surface lapping step is performed before the inner peripheral end surface polishing step. 3. The method for polishing a glass substrate for an information recording medium according to claim 1, wherein said recording surface lapping step is performed after said inner peripheral end face polishing step. 4. The method according to claim 1, wherein at least one of the outer peripheral end face polishing step and the inner peripheral end face polishing step comprises a step of polishing the work with a rotating brush in a state where the works are stacked one by one with a spacer interposed therebetween. The method for polishing a glass substrate for an information recording medium according to claim 1. 5. The method according to claim 1, wherein at least one of the inner peripheral end face polishing step and the inner peripheral end face polishing step comprises a step of polishing the work with a rotary brush, and the brush tip of the rotary brush has a mountain shape. Claims 1 to 3
The method for polishing a glass substrate for an information recording medium according to any one of the above items. 6. At least one of the inner peripheral end face polishing step and the inner peripheral end face polishing step includes a step of polishing the work with a rotating brush, wherein the rotating brush has a direction of bristles chamfering the glass substrate. The method for polishing a glass substrate for an information recording medium according to any one of claims 1 to 3, wherein the method is configured to be oriented along a surface. 7. A glass substrate for an information recording medium, polished by the method for polishing a glass substrate for an information recording medium according to claim 1.