| 摘要 |
PROBLEM TO BE SOLVED: To increase the strength of a substrate by forming the substrate with a doughnut shaped single crystal silicon plate and setting the average surface roughness of the inner and the outer peripheral end faces to be less than a specific value. SOLUTION: A single crystal silicon is sliced and hollowed out in a doughnut shape. Then, the end faces of the inner and the outer peripherals are ground and chamfered. Then, an etching is conducted by sodium hydroxide and the substrate surface is ground so that an average surface roughness Ra of the inner and the outer peripheral end faces is set to less than 0.4μm to produce the substrate. By making the roughness Ra to be less than 0.4μm, the bending strength is greatly increased compared with the substrate having the roughness Ra of more than 0.4μm. It is desireable to use a single crystal or the substrate from the strength point of view. Moreover, it is also desirable to make the roughness Ra of the tilted surface, on which a chamfering is performed, to be less than 0.4μm. Thus, a stronger magnetic recording medium is produced and the size of a computer is further reduced.
|
