Method for manufacturing glass substrate for magnetic recording medium
A method for manufacturing a glass substrate for a magnetic recording medium, including a polishing step of polishing a principal surface ( 12 ) of a glass substrate ( 10 ) having a chamfered surface ( 16 ) formed on an end surface of the glass substrate ( 10 ), with use of a polishing pad ( 24 ) having a concave groove ( 31 ) formed in a surface ( 24 a ) for supplying a polishing solution, the polishing step is performed in the following condition: 10°≦θ p<θd≦80° where θd is an angle defined by the chamfered surface ( 16 ) and a plane in parallel to a thickness direction of the glass substrate ( 10 ) on an inner side portion of the glass substrate ( 10 ), and θp is an angle defined by a concave groove side surface ( 31 a ) and a plane in parallel to a thickness direction of the polishing pad ( 24 ) on an inner side portion of the polishing pad ( 24 ).
1. A method for manufacturing a glass substrate for a magnetic recording medium, the method comprising:
providing a glass substrate having a chamfered surface formed on an inner peripheral end surface and/or an outer peripheral end surface of the glass substrate; and
polishing a principal surface of the glass substrate with use of a polishing pad having a concave groove formed in a surface of the polishing pad for supplying a polishing solution, wherein the polishing is performed in the following condition:
10°≦θ p<θd≦ 80°
where
θd is an angle defined by the chamfered surface and a plane in parallel to a thickness direction of the glass substrate on an inner side portion of the glass substrate, and
θp is an angle defined by a side surface of the concave groove and a plane in parallel to a thickness direction of the polishing pad on an inner side portion of the polishing pad.
2. The method for manufacturing a glass substrate for a magnetic recording medium according to claim 1 , wherein the polishing pad is a suede-type soft polishing pad having a polishing layer formed of foamed polyurethane.
3. The method for manufacturing a glass substrate for a magnetic recording medium according to claim 1 , wherein a polishing solution containing silica as abrasive grains is used in the polishing step.
4. The method for manufacturing a glass substrate for a magnetic recording medium according to claim 1 , wherein the polishing pad has an Asker C hardness in a range of from 60 to 85.
5. The method for manufacturing a glass substrate for a magnetic recording medium according to claim 1 , wherein the polishing is performed in accordance with the following condition:
25°≦θp<θd≦65°.
6. The method for manufacturing a glass substrate for a magnetic recording medium according to claim 1 , wherein a curvature of a corner portion of the glass substrate between the principal surface and the chamfered surface is greater than or equal to 0.05 mm.
7. The method for manufacturing a glass substrate for a magnetic recording medium according to claim 1 , wherein θp and θd are chosen such that should the glass substrate fall in the groove a corner portion of the glass substrate between the principal surface and the chamfered surface is prevented from contacting the groove.
8. The method for manufacturing a glass substrate for a magnetic recording medium according to claim 1 , wherein θp and θd are chosen such that should the glass substrate fall in the groove a corner portion of the glass substrate between the principal surface and the chamfered surface is prevented from being worn into a round shape.
9. The method for manufacturing a glass substrate for a magnetic recording medium according to claim 1 , wherein θp and θd are chosen such that when the polishing solution is supplied to the polishing pad via the groove, the polishing solution is smoothly supplied onto the polishing pad.
10. The method for manufacturing a glass substrate for a magnetic recording medium according to claim 1 , wherein the concave groove comprises a planar side that extends along a length of the groove.
11. The method for manufacturing a glass substrate for a magnetic recording medium according to claim 10 , wherein the concave groove comprises a second planar side that faces the planar side and extends along the length of the groove.
12. The method for manufacturing a glass substrate for a magnetic recording medium according to claim 11 , wherein a height of the planar side is different in value than a height of the second planar side.
13. The method for manufacturing a glass substrate for a magnetic recording medium according to claim 11 , wherein the planar side and the second planar side contact each other.
14. The method for manufacturing a glass substrate for a magnetic recording medium according to claim 13 , wherein a height of the planar side is different in value than a height of the second planar side.