Method of manufacturing magnetic-disk glass substrate and method of manufacturing magnetic disk

Abstract

A process for producing a glass substrate for magnetic disk through chemical strengthening operation, in which the distribution of compressive stress is uniformed at a surface layer portion. The chemical strengthening operation includes the first step of bringing the glass substrate into contact with a first treatment solution (chemical strengthening treatment solution) containing first ions with an ionic radius larger than those of ions within the glass substrate and either the second and subsequent steps of bringing the platy glass into contact with treatment solutions containing second and subsequent bivalent ions, or the second and subsequent steps of bringing the glass substrate into contact with second and subsequent chemical strengthening treatment solutions containing second and subsequent ions exhibiting an ion exchange rate with ions within the glass substrate greater than that of the first ions to thereby decelerate the ion exchange.

1 . A method of manufacturing a magnetic-disk glass substrate, the method including a chemical strengthening process of chemically strengthening the glass substrate, wherein:
 the chemical strengthening process comprises at least two steps;   a first step brings the glass substrate into contact with a chemical strengthening treatment solution containing first ions having an ionic radius larger than an ionic radius of ions contained in the glass substrate, thereby causing ion exchange to occur; and   a second or subsequent step brings the glass substrate into contact with a treatment solution containing second or subsequent ions being bivalent ions.   
     
     
         2 . The method of manufacturing the magnetic-disk glass substrate according to  claim 1 , wherein:
 the second or subsequent ions are any one of Pb2+, Cd2+, Zn2+, Hg2+, Ca2+, Sr2+, and Ba2+.   
     
     
         3 . The method of manufacturing of the magnetic-disk glass substrate according to  claim 1 , wherein:
 a maximum value of fine waviness of a main surface of the glass substrate is less than 5 nm in a rectangular measurement range having sides of 800 μm and 980 μm.   
     
     
         4 . A method of manufacturing a magnetic disk, comprising:
 forming at least a magnetic layer on the magnetic-disk glass substrate manufactured by the magnetic-disk glass substrate manufacturing method according to  claim 1 .