2311 Changes in Friction Properties of Thin Lubricant Films on Magnetic Disks Accompanying with the Formation of Bonded Molecules

Abstract

To ensure the reliability and durability of hard disk drives, molecularly thin polymeric liquid films of perfluoropolyether (PFPE) coated on the disk surfaces possess a mixed structure consisting of molecules bonded to the disk surfaces and non-bonded mobile molecules. Aiming to clarify the influence of film composition (mobile/bonded) on tribological performance, we measured friction properties of two types of 2-nm-thick PFPE films (polar Zdo12000 and nonpolar Z03) under lightly loaded (loading force: 0-1mN) and quasi-static (rotational speed: 2.1mm/s) conditions as a function of elapsed time. The friction force of Z03 remained unchanged with time and it increased linearly with loading force. In contrast, accompanying with the development of bonded molecules over time, the fiction force of Zdo12000 increased with time and transited to a nonlinear increase with loading force as the time proceeded.