JP2002210640A - Polishing method for disk substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing method that can reduce a surface sag near a disk periphery. SOLUTION: The polishing method for a disk substrate 1 holds with pressure both obverse and reverse surfaces of the disk substrate 1 of an outside diameter D1 and an inside diameter D2 between a pair of rotary polishing elements opposed on both surfaces of the substrate to thus polish them simultaneously. The substrate is held by an attitude holding means and is forcibly rotated. The pair of rotary polishing elements meet a relation of a diameter D (D>D1-D2). The axis of rotation of the polishing elements is offset at (a) outside the outer circumference of the substrate to even out polishing removals between the inner and outer circumferences of the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for polishing a disk made of metal, ceramics, glass or the like using a pair of rotary abrasives. In particular, the present invention relates to a polishing method suitable for a glass substrate or an aluminum alloy substrate used for a hard disk.

[0002]

2. Description of the Related Art As a method of polishing both front and back surfaces of a glass disk, Japanese Patent Application Laid-Open No. Hei 6-210560 discloses a method in which a glass disk is held in a vertical position by three cylindrical rotating rollers, and is smaller than the diameter of the glass disk. While sandwiching the glass disk between a pair of rotating abrasive bodies having a diameter, the rotating abrasive body is rotated and reciprocated about a rotation axis along the axis of the glass disk to simultaneously polish both front and back surfaces of the glass disk. A method and apparatus are described.

[0003]

[0005] By the way, in a hard disk, an increase in its storage capacity is increasingly required. In particular, it is required that a disk substrate can be used as a data zone up to the outermost end.

Therefore, in order to use the disk substrate just to the outer peripheral edge, in a polishing apparatus disclosed in Japanese Patent Application Laid-Open No. 2000-326216, a baffle plate slightly thinner than the thickness of a glass disk is provided between opposing rotating polishing bodies. Is disclosed. Thereby, it is said that surface droop near the outer periphery of the glass disk can be reduced.

Incidentally, the above-mentioned Japanese Patent Application Laid-Open No. Hei 6-21056 has been disclosed.
In the double-head polishing apparatus and the polishing method disclosed in Japanese Patent Application Laid-Open No. 2000-326216 or No. 2000-326216, the mechanism of polishing in the central portion and the vicinity of the outer periphery of the main surface of the disk when polishing the disk substrate has not been studied in detail. Was.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of polishing a disk substrate, in particular, a method of reducing surface sagging near the outer periphery of a disk.

Another object of the present invention is to provide a polishing method capable of averaging the amount of polishing from the inner circumference to the outer circumference of the disk substrate.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention has considered to equalize the polishing amount from the inner peripheral edge to the outer peripheral edge of the disk substrate. As a specific solution, the rotational axis of the polishing body is offset outside the outer peripheral edge of the disk substrate, and the relative speed between the disk and the pad is averaged from the inner peripheral edge to the outer peripheral edge of the disk substrate. The polishing amount was averaged.

That is, according to the present invention, a disk substrate having an outer diameter D1 and an inner diameter D2 is sandwiched between a pair of rotary abrasive bodies provided opposite to both surfaces of the substrate. In the method of polishing a disk substrate to be polished at the same time, the substrate is held by a posture holding means and is forcibly rotated, and the pair of rotary abrasive bodies have a relationship of a diameter D (D> D1−D2). Satisfied,
A disk substrate polishing method, further comprising offsetting a rotation axis of the polishing body to an outside of an outer peripheral edge of the substrate and averaging a polishing amount from an inner peripheral edge to an outer peripheral edge of the substrate.

According to a second aspect of the present invention, there is provided the disk substrate polishing method according to the first aspect, wherein the offset amount is optimized.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below. Figure 1
1 is an overall view of an embodiment of a double-side polishing apparatus to which the present invention can be applied. The double-side polishing apparatus 50 includes a gantry 5 and the gantry 5
Vertical holding means 4 for holding the disk substrate 1 in a vertical position, which is disposed at the center of the disk drive, and rotating abrasive bodies 2a, 2b disposed on both sides of the holding section 4.

A pair of rotary polishing members are mounted on a gantry 5 such that both sides of the disk substrate 1 held in a vertical position by the rollers 3 are sandwiched and the rotation axis thereof is parallel to the rotation axis of the disk substrate 1. The bodies 2a, 2b are arranged.

The rotary abrasive body 2a is rotatably supported by a rotary shaft cylindrical body 13 supported by a bearing body 14a fixed to the gantry 5.
a. The rotation of the electric motor 7a fixed by a support (not shown) is performed by a belt connecting the pulley 16a attached to the rotating shaft of the electric motor and the pulley 15a attached to the end of the rotating shaft cylinder 13a. It is transmitted to the rotary abrasive body 2a via 8a. A polishing liquid supply hole 6 for supplying the polishing liquid 17 in the storage tank 18 to the inside of the rotary polishing body 2a by the transport pump 9 is provided in the rotary shaft of the rotary shaft cylinder 13a and the pulley 15a.

The rotary abrasive body 2b is rotatably supported by a bearing body 14b supported by a slider portion 12 that moves while sliding in the left-right direction on a rail 10 provided on the gantry 5. It is fixed to. The electric motor 7b is rotated by a pulley 16b attached to a rotating shaft of the electric motor, a pulley 16b and a rotating shaft cylinder 13b.
8 connecting pulley 16b attached to the end of
b to the rotating abrasive body 2b.

Means for contacting at least one of the pair of rotary abrasive bodies 2a and 2b against the disk substrate 1 is provided. The applying means is not particularly limited as long as it has a function of pressing the rotating abrasive body 2 against the polishing surface of the disk substrate 1 at a predetermined pressure. In FIG. 1, a bearing 1
4 includes a slider unit 12 for supporting the slider 4, a rail 10 for sliding the slider unit 12 in the left-right direction, and a pressing device 11 having an air cylinder.
The rotating abrasive body 2b can be moved toward and away from the disk substrate 1 by driving the motor of the pressing device 11, and is brought into contact with the disk substrate 1 with an appropriate pressure.

In FIG. 1, the rotating abrasive body 2a is fixed in the left-right direction, and the rotating abrasive body 2b is movable in the left-right direction by a contact means. The disk substrate 1 is applied in a pressed state by a pair of rotating abrasive bodies 2 being rotated,
The polishing liquid is supplied in this pressed state, and the grinding and polishing are performed. The vertical posture holding means 4 of the disk substrate 1 holds the disk substrate 1 with at least three rollers sandwiching the outer peripheral surface thereof.

FIG. 2 is a view showing one embodiment of the vertical attitude holding means 4 of the disk substrate 1 and the motor 19 for forced rotation of the double-side polishing apparatus of the present invention. FIG. 2 shows a state in which three rollers 3a, 3b, and 3c rotatably mounted and a roller 3d for forcibly rotating one disk substrate are held. The thickness of each roller 3 (in the direction perpendicular to the plane of the paper) is sufficiently larger than the thickness of the disk substrate 1. A disk substrate 1 is provided on the outer peripheral surface of each roller 3.
A groove having a width slightly larger than the thickness of the disk substrate 1 may be provided to facilitate removal of the disk substrate 1 from the holding means or attachment of the holding means. Upper two rollers 3
a and 3c are supported by a supporting bracket 44 via a moving bracket 43 movably attached by sliding the cross beam 42 along the length direction so that the rotation axis of each roller is horizontal. Have been. Lower rollers 3b, 3d
Is attached to the column 41.

FIG. 3 is a diagram for explaining the positional relationship between the disk substrate 1 having the outer diameter D1 and the inner diameter D2 and the rotational axis of the rotary abrasive body 2. As shown in FIG. FIG. 3 shows a state in which the disk substrate 1 is held in a vertical position by being sandwiched between the outer peripheral surfaces of the three rollers 3a, 3b, 3c on the outer peripheral surface. The rotation axis of one of the rotary abrasive bodies 2a can move in parallel with the rotation axis of the disk substrate 1 so that the distance a can be adjusted. At this time, in the present invention, when the diameter of the rotary polishing body 2a is D, it is necessary that D> D1−D2.

The rotary abrasive body 2 may be a metal or ceramic surface plate with a polishing pad attached thereto, or a surface plate to which a diamond grindstone of a predetermined grain size is attached. FIGS. 4A and 4B are a plan view and a cross-sectional view of an embodiment of a rotary abrasive body that can be used in the present invention. In FIG. 4A, a groove 22 connected to the polishing liquid supply hole 6 is radially provided on one surface of the metal disk 20 toward the outer periphery of the platen. The groove 22 may have a spiral shape or a lattice shape.

A polishing pad 21 made of resin is adhered to the surface of the platen. The polishing liquid supplied from the polishing liquid supply hole 6 is supplied onto a groove formed by attaching the polishing pad 21 so as to follow the surface of the groove formed on the surface of the surface plate 20. The polishing pad 21 does not necessarily have to be adhered in close contact with the inner surface of the groove 22 of the surface plate, and may be bonded in a state where there is a gap between the groove 22 of the surface plate and the polishing pad 21.

This is because a polishing load is not applied to the surface of the polishing pad in the groove during the polishing process, so that the polishing liquid is supplied along the groove. When a diamond grindstone is stuck to a surface plate to form a rotary abrasive body, it is preferable that the diamond grindstone pieces to be stuck have grooves as described above.

The abrasive used in the polishing method of the present invention includes cerium oxide having an average abrasive of about 0.2 μm to 2 μm, diamond abrasive, silicon carbide abrasive, alumina abrasive, zirconia abrasive, Manganese abrasive grains, iron oxide abrasive grains, etc. dispersed in pure water or alkaline liquid,
Colloidal silica having an average particle size of about 0.02 μm to 0.2 μm can be used. Further, fixed abrasive grains such as a diamond grindstone may be used.

As the polishing pad for holding the polishing agent, a sheet-like pad such as a urethane suede pad, a foamed urethane pad, or a non-woven fabric pad can be used. Further, a polishing pad having a groove formed by machining or hot pressing may be used.

(Embodiment) Using the double-side polishing apparatus shown in FIG. 1, an outer diameter is 65 mm, an inner diameter is 20 mm, and a thickness is 0.65 m.
For a disk substrate made of aluminosilicate glass having a thickness of m, polishing was performed while changing the offset amount described later.
The polishing conditions are as follows.

1) Rotary polishing body: A polishing pad made of urethane suede (product name: Seagull 1900, manufactured by Daiichi Race Co., Ltd.) adhered to a stainless steel surface plate having a diameter of 70 mm. 2) Surface plate: As shown in FIG. 4, width 5 mm, depth 0.5 m
The one provided with six grooves each having an m-shaped cross section. 3) Supply of polishing liquid Supply through the groove from the axis: A polishing liquid supply hole provided in one of the rotation axes of the rotary polishing body is obtained by dispersing cerium oxide having an average particle size of about 1 μm in pure water. And supply 3-10 mL per minute. 4) Number of rotations of the rotary abrasive body: 800 rpm 5) Number of rotations of the disk substrate: 1000 rpm 6) Pressing force of the rotary abrasive body: about 5 kgf 7) Distance between the center of rotation of the disk substrate and the rotation axis of the rotary abrasive body: 25 mm 8) Distance from the outer edge of the disk substrate to the axis of rotation of the rotary abrasive body (offset amount) a: -10 mm to +10 mm

FIG. 5 shows the result of the relative polishing amount depending on the radial position of the disk. The vertical axis in FIG. 5 is the relative polishing amount. As can be seen from the drawing, the amount of polishing from the inner peripheral edge to the outer peripheral edge of the disk substrate can be averaged by offsetting the rotation axis of the rotary abrasive body to the outside of the disk outer periphery.

That is, it is understood that the optimum offset amount in the above-mentioned 65 × 20 mm disk substrate is 6 mm.

Further, the optimum offset amount can be calculated as follows. That is, the following procedure is performed. (1) Input parameters. The outer diameter of the pad, the number of rotations of the pad, the outer diameter of the disk, the inner diameter of the disk, the number of rotations of the disk, the offset amount (2) The relative speed difference between the disk and the pad at the outer diameter from the inner diameter is calculated. (3) The obtained relative speed difference is integrated to evaluate the polishing amount. (4) The polishing amount is sequentially evaluated by changing the offset amount.

As described above, the optimum offset amount can be obtained by changing the offset amount and obtaining the relationship between the inner diameter and the outer diameter of the disk and the polishing amount.

Further, the optimum offset amount can be similarly obtained for disk substrates having various inner and outer diameters.

[0031]

According to the present invention, in the method for polishing a disk substrate, the rotation axis of the polishing body is offset to the outside of the outer peripheral edge of the disk substrate, and the amount of polishing from the inner peripheral edge to the outer peripheral edge of the disk substrate can be averaged. Therefore, surface sagging near the outer periphery of the disk substrate can be prevented.

Furthermore, the amount of polishing from the inner peripheral edge to the outer peripheral edge of the disk substrate can be averaged, so that the disk substrate can be efficiently polished.

[Brief description of the drawings]

FIG. 1 is an overall side view of a double-side polishing apparatus to which the present invention can be applied.

FIG. 2 is a view for explaining one mode of a vertical attitude holding means and a forced rotation means of a disk substrate.

FIG. 3 is a diagram showing a positional relationship between a disk substrate and a rotary polishing body according to the polishing method of the present invention.

FIG. 4 is a plan view and a cross-sectional view of an embodiment of the rotary abrasive body.

FIG. 5 is a graph showing a relationship between an offset amount and a polishing amount.

[Explanation of symbols]

 1: Disk substrate 2: Rotary polishing body 3: Roller 4: Vertical posture holding means 5: Stand 6: Polishing liquid supply hole 7: Electric motor 8: Belt 9: Transport pump 10: Rail 11: Pressing device 12: Slider section 13 : Rotating shaft cylinder 14: Bearing body 15, 16: Pulley 17: Polishing liquid 18: Storage tank 19: Motor for forced rotation 20: Surface plate 21: Polishing pad 22: Groove 41: Post 42: Cross beam 43: Moving fitting 44 ： Support bracket 50 ： Polishing device

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference)

Claims (2)

[Claims] 1. A method for polishing a disk substrate in which both front and rear surfaces of a disk substrate having an outer diameter D1 and an inner diameter D2 are sandwiched by a pair of rotary abrasive bodies provided opposite to both surfaces of the substrate and simultaneously polished. The substrate is held by the posture holding means and is forcibly rotated, and the pair of rotating abrasive bodies have a diameter D satisfying a relationship of (D> D1−D2), and further, the rotation axis of the abrasive body is A method for polishing a disk substrate, characterized in that the amount of polishing from the inner peripheral edge to the outer peripheral edge of the substrate is averaged, offset to the outside of the peripheral edge of the substrate. 2. The disk substrate polishing method according to claim 1, wherein said offset amount is optimized.