Method of manufacturing magnetic recording medium glass substrate

Abstract

Provided is a magnetic recording medium glass substrate manufacturing method capable of manufacturing a magnetic recording medium glass substrate having high surface smoothness and low surface waviness with productivity. In a primary lapping process and a secondary lapping process of the manufacturing method, diamond pads ( 20 A and 20 B) in which diamond abrasive grains are fixed by a binder are used. A plurality of convex portions ( 21 ) with a flat top are arranged in a tile shape on a lapping surface ( 20 a ) of each of the diamond pads ( 20 A and 20 B). In the diamond pad ( 20 A) used in the primary lapping process, the average diameter of the diamond abrasive grains is in the range of 4 μm to 12 μm and the content of the diamond abrasive grains in the convex portion ( 20 A) is in the range of 5 vol % to 70 vol %. In the diamond pad ( 20 B) used in the secondary lapping process, the average diameter of the diamond abrasive grains is in the range of 1 μm to 5 μm and the content of the diamond abrasive grains in the convex portion ( 20 B) is in the range of 5 vol % to 80 vol %.

1 . A method of manufacturing a magnetic recording medium glass substrate comprising:
 a step of performing a primary lapping process on a surface of the glass substrate except for at least an end surface; and   a step of performing a secondary lapping process on the surface of the glass substrate,   wherein the primary lapping process and the secondary lapping process use diamond pads in which diamond abrasive grains are fixed by a binder,   a plurality of convex portions with a flat top are arranged in a tile shape on a lapping surface of the diamond pad,   in the diamond pad used in the primary lapping process, the average diameter of the diamond abrasive grains is in the range of 4 μm to 12 μm and the content of the diamond abrasive grains in the convex portion is in the range of 5 vol % to 70 vol %, and   in the diamond pad used in the secondary lapping process, the average diameter of the diamond abrasive grains is in the range of 1 μm to 5 μm and the content of the diamond abrasive grains in the convex portion is in the range of 5 vol % to 80 vol %.   
     
     
         2 . The method of manufacturing a magnetic recording medium glass substrate according to  claim 1 ,
 wherein, in the diamond pads used in the primary lapping process and the secondary lapping process, the convex portion has outside dimensions including a size of 1.5 mm to 5 mm×1.5 mm to 5 mm and a height of 0.2 mm to 3 mm, and a gap between adjacent convex portions is in the range of 0.5 mm to 3 mm.