Effects of End Groups on the Spreading Characteristics of Molecularly Thin Liquid Lubricant Films in Hard Disk Drives

Abstract

The spreading characteristics of novel alkanolamine-terminated perfluoropolyether (PFPE) films on carbon surfaces were investigated experimentally by using a scanning micro-ellipsometer. The apparent diffusion coefficients of the novel lubricants were studied in order to evaluate the spreading speed and they were compared with the conventional Z-dol, Z-tetraol, and A20H lubricants. It was found that the mobility of a lubricant is lower when the number of OH end groups is higher. It was also found that the mobility of the alkanolamine-terminated PFPE films was lower than that of conventional lubricants with the same number of OH end groups as that of the alkanolamine-terminated lubricants and that the mobility tendency of the lubricants has a good correlation with their viscosity tendency. In addition, the mobility of ZDPA with a dipropylamine end group (no OH end group) has peculiar characteristics. Its mobility is higher than that of Z-dol when the film thickness of the lubricant exceeds that of one monolayer. However, it is lower than that of Z-dol when the film thickness of the lubricant is less than that of one monolayer. This may be due to the unique interaction between the ZDPA amine group and the carbon overcoat.

Bonding Mechanism of Perfluoropolyether Lubricant Film with Functional Endgroup on Magnetic Disks by Ultraviolet Irradiation

“…We could estimate the more particular mechanism as following. It has been shown by many studies [8][9][10][11][12] that the disposition of PFPE with OH-containing end groups of the first monomolecular layer in contact with the carbon overcoat is such that the end groups are held to the carbon surface via hydrogen bonding with the OH units of the carbon surface. Thus, the conduction band of the carbon on anti-bonding orbitals extends into the OH-containing end group.…”

Laser-Induced Thermo-Desorption of Perfluoropolyether Lubricant from the Surface of a Heat-Assisted Magnetic Recording Disk: Lubricant Evaporation and Diffusion

“…For a reliable recording surface, lubricant molecules must diffuse to regions of the disk surface that have had lubricant removed or greatly thinned through mechanical or thermal means [28][29][30][31][32]. Figure 1 quantifies the evolution of the lubricant film after the initial depression in the lubricant is created and can be used to determine the diffusion rate.…”