Ultra-Smoothness Polishing of Glass Magnetic Disk Substrate (1st Report)

Abstract

The research deals with the ultra-smoothness polishing technique of a glass type of magnetic disk substrate. The influence of polishing pressure on the removal rate and smoothness in polishing of a glass type of substrate with cerium oxide abrasives is experimentally examined and discussed. The substrate surface roughness is measured with a contact type of ordinary profilometer, interferometric surface profiler and AFM. The substrate smoothness is evaluated from the standpoint of the slight undulation Hw(Rz) and the surface roughness Hr(Rz), which are obtained by measuring 4mm and 250μm in the length of substrate surface, respectively. The substrate removal depth increases linearly with polishing time. The substrate removal rate becomes larger for higher polishing pressure. Over a critical polishing pressure, the removal rate is expressed by a simple equation related to polishing pressure. The slight undulation and surface roughness converge finally to a terminal value corresponding to a given polishing pressure, respectively. The terminal slight undulation increases somewhat with polishing pressure. The terminal surface roughness, on the other hand, is influenced little by polishing pressure.