Mieko Ishii

Simultaneous measurement of pin wear and change in lubricant thickness on thin-film magnetic disks

The relation between head wear and disk-lubricant thickness was studied by transparent pin wear tests on thin-film magnetic disks while making simultaneous micro-ellipsometer measurements to determine changes in lubricant thickness. As-dipped and rinsed lubricant disks were prepared to study the effects of free and adsorbed lubricants. On the rinsed disk without free lubricant, pin wear started after one minute of sliding, and the decrease in lubricant thickness on the sliding track was small. On the as-dipped disk with free lubricant, pin wear started after 30 minutes of sliding, and was less pronounced than that on the rinsed disk, while lubricant thickness decreased until wear started, and became constant thereafter. The decrease in lubricant thickness was greater than that on the rinsed disk. Free lubricant was shown to reduce pin wear. The replenishment of lubricant was also measured. A model of pin wear and change in lubricant thickness is proposed taking into account disk-surface roughness and the replenishment of free lubricant.

Lubricant behavior and pin wear on thin-film magnetic disks

Transparent-pin wear tests with in-situ microellipsometer measurement were performed on thin-film magnetic disks with different lubricants. We found that pin wear started when the decrease in the lubricant thickness at the pin slide-path leveled-off and that pin wear sometimes started when the lubricant thickness was still larger than that of the adsorbed lubricant. These mean that the free lubricant on the disk surface is not replenishing the real points of pin-disk sliding. Consequently, we considered that the replenishment of free lubricant to the real points of pin sliding is more important than the fact whether the average lubricant thickness exceeds the adsorbed lubricant thickness or not. Tests on disks with different lubricants show that the lower the lubricant viscosity, the greater the lubricant loss and the smaller the pin wear. We find that a low-viscosity-lubricant is better in replenishing free lubricant to the real points of sliding than high-viscosity-lubricant is.

Effects of sliding pin shapes on change in thin-film disk lubricant thickness

To analyze lubricant loss by head sliding, change in lubricant thickness during sliding under a flat-circular-surface pin (FC pin) on a thin-film magnetic disk is compared with that of a spherical-surface pin (S pin). Lubricant pick-up onto the PC pin was much smaller than that onto the S pin. And the amount of lubricant loss under the FC pin was smaller than that under the S pin. We consider the cause of this is the difference in the angle of the side wall at the trailing edge of the pins.

Sliding-pin shapes and lubricant thickness change on a thin-film magnetic disk

Abstract In developing hard disk drives, it is necessary to keep lubricant as thick as possible during operations. For this purpose, we studied lubricant loss under different-shape contact-sliders on thin-film magnetic disks by using transparent-pin sliding tests with a built-in ellipsometer. We compared sliding pins with spherical, flat circle, flat square, and double-flat-rail surfaces. We found that lubricant loss was smaller under flat pins than under the spherical pin, and the smallest under the double-flat-rail pin among flat sliders. The results show that the horizontal and vertical shapes of sliders must carefully be selected for contact recording systems.