Clamping jig for glass substrate, buffer sheet, method for processing glass substrate, and glass substrate

Abstract

The present invention provides a method which can simultaneously grind inner peripheral edges and outer peripheral edges of a multiplicity of glass substrates used for magnetic storage media or the like. In order to chamfer the outer edges of the glass substrates g, a multiplicity of annular glass substrates g are firstly stacked with buffer sheets 5 interposed between the glass substrates to make a glass substrate block G. Then, a first plates 1, 1 of the above described clamping jig are applied to both sides of the glass substrate block G, and a first fastening tool 3 is inserted through center holes of the first plates 1, 1 and the glass substrate block G. Next, the glass substrate block G is clamped from an inside thereof for chamfering the outer edges with a grindstone 6.

Description

[0001] 1. Field of the Invention[0002] The present invention relates to a clamping jig for holding a multiplicity of annular glass substrates with the annular glass substrates being stacked, a buffer sheet to be interposed between the glass substrates, a method for grinding (chamfering or polishing) inner peripheral edges and outer peripheral edges of the multiplicity of annular glass substrates, and a glass substrate obtained by this method.[0003] 2. Description of the Related Art[0004] Glass is superior to aluminum in shock resistance, rigidity, hardness, and strength, so that the glass has been increasingly used as a magnetic storage medium which is built into a hard disc drive or the like.[0005] In particular, a configuration of a personal computer has been gradually changed from a desktop type to a notebook type or a mobile type recently, thus the demand for glass substrates which are excellent in flatness and densification has been increased instead of aluminum substrates.[000...

AI Technical Summary

Benefits of technology

[0010] Secondly, cracks are easily produced on the recording surfaces since the glass substrates are directly contacted with each other. That is, a great amount of cullets (glass powder) are produced in a working field of the polishing, so that the cullets may be interposed between the glass substrates, and consequently, a pressure applied by the clamp to the glass substrates causes deep cracks (25 .mu.m or more) on the surfaces. In this way, the presence of the cracks on the recording surface of the glass substrate has a disadvantage for forming a uniform magnetic film, so that the polishing has to be continued until the cracks disappear. The polishing time becomes longer when a polishing margin becomes thicker, and the glass substrate itself also requires to be manufactured in consideration of the polishing margin, so that the glass substrate inevitably becomes thicker.

[0013] And in a method for processing a glass substrate according to the present invention, a stack of a multiplicity of annular glass substrates is clamped at an outer side or an inner side thereof while buffer sheets are respectively interposed between the annular glass substrates such that the buffer sheets do not protrude from inner peripheral edges and outer peripheral edges of the glass substrates, the outer peripheral edges of the multiplicity of glass substrates are simultaneously ground with the stack being clamped at the inner side thereof, the inner peripheral edges of the multiplicity of glass substrates are simultaneously ground with the stack being clamped at the outer side thereof, and further, the clamping situation of the glass substrates is maintained even at a time of switching between an operation for grinding the above described inner peripheral edges and an operation for grinding the above described outer peripheral edges.

[0018] Setting the inner and outer diameters within a range described above is required to prevent poor lapping or poor polishing, and setting the thickness at 0.2 mm or less provides an RC (Radial Curvature) of 40 nm or less.

Problems solved by technology

The above described method is ineffective because the glass substrates should be processed every single substrate.

However, the prior art as described above has problems as follows.

However, the processing becomes inefficient when the polishing is conducted every single substrate, on the other hand, the use of another damper not only complicate the polishing steps but also causes misalignment of centers of the glass substrates at a time of newly holding the glass substrates by the another clamper, so that the processing precision deteriorates.

Secondly, cracks are easily produced on the recording surfaces since the glass substrates are directly contacted with each other.

That is, a great amount of cullets (glass powder) are produced in a working field of the polishing, so that the cullets may be interposed between the glass substrates, and consequently, a pressure applied by the clamp to the glass substrates causes deep cracks (25 .mu.m or more) on the surfaces.

In this way, the presence of the cracks on the recording surface of the glass substrate has a disadvantage for forming a uniform magnetic film, so that the polishing has to be continued until the cracks disappear.

The polishing time becomes longer when a polishing margin becomes thicker, and the glass substrate itself also requires to be manufactured in consideration of the polishing margin, so that the glass substrate inevitably becomes thicker.

If foreign substances such as cullets are present between the glass substrates g, cracks may be produced on the recording surface when the glass substrates g are directly stacked to each other.

However, the quality of the glass substrates may be affected, if such portions which have not been sufficiently polished exist excessively.

It is extremely difficult to remove the sheet from the glass.

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