Water Adsorption and Friction on Thin Film Magnetic Recording Disks~©

摘要

Water adsorption isotherms were measured with two differentrntypes of perfluropolyether lubricants, Zdol 4000 and Ztetraolrn2000, on thin film magnetic recording disks. The adsorptionrnisotherm provides the average water film thickness (areal density)rnas a function of relative humidity. The water film thickness wasrnmeasured while varying the relative humidity (RH) in the rangernfrom dry air to 85%. The water film thickness for both types ofrnlubricants increased with RH, and was independent of temperaturernbetween 20° and 50℃. The water film thickness at saturationrnRH was typically 0.44 nm (16m~2) for Zdol and 0.25 nm (9m~2)rnfor Ztetraol. Friction measurements were performed on the samernset of disks up 70% RH. The maximum friction increased with RH,rnmore for Zdol than for Ztetraol, and the friction with Ztetraol wasrnmuch less than with Zdol. Brief exposure to condensing RH dramaticallyrnaltered the friction and acoustic emission even at relativelyrnhigh slider flying height. The altered frictional propertiesrnwere associated with liquid nanodroplets formed on the disks duringrnthe brief condensation.