Depletion and Replenishment of Molecularly Thin PFPE Lubricant Film on DLC Surface of Magnetic Disks

摘要

Depletion and replenishment characteristics of molecularly thin perfluoropolyether (PFPE) lubricant film were studied using a pin-on-disk sliding test using a glass ball and magnetic disks coated with hydrogenated diamondlike carbon. Depletion and accumulation of the lubricant film after sliding tests performed with or without seek motion and recovery processes toward original flat surface were measured using an optical surface analyzer (OSA). An anomalous phenomenon of polar lubricant unrecoverable against lubricant depletion was observed first. This phenomenon occurs when the residual film thickness after depletion nearly equals a monolayer of a polar PFPE molecule independent of initial film thickness. In addition, recovery rates, defined as the ratio of depletion area or accumulation area to their initial values, were quantified for polar and nonpolar lubricants. The recovery rates are found to have a nearly linear relationship with varying elapsed time expressed in a logarithmic scale.