Lubricant spin-off from magnetic recording disks

As the rotation rate of magnetic recording disks increases over the next few years, lubricant spin-off from the disk surface may be significant. Lubricant thickness was measured as a function of spin time at 10 000 rpm on typical carbon overcoated magnetic recording disks initially lubricated with 10-135 Å of perfluoropolyether Zdol. The viscosity of the lubricant film increased as the film thickness decreased with spin time. Lubricant spin-off in response to air shear stress on the free surface was approximately described by viscous flow. The rate of lubricant removal by evaporation was compared to the spin-off removal rate in films between 10 and 50 Å thick. Dispersion interaction and chemisorption are expected to retain a molecularly thin film of lubricant on the disk surface.