Head disk interface of high capacity floppy disk "HiFd"

Abstract

IutroductionHiFD is the floppy disk which combines a 200MB capacity with full downward compatibility with conventional 3.5" FD [I]. The technology of hard disk is moving toward pseudo-contact remrding and the flying height has been reduced [2]. On the other hand, conventional 3.5" FD is contact recording. HiFD system tries to achieve pseudo-contact recording by increasing the rotation speed to 3600rpm. Numerous studies have been pursued to examine head-disk interface (HDI) of hard disk. There were, however, few studies of HDI of floppy disk under high rotation speed. In this paper, we discuss the friction force between the head and the floppy disk under high rotation speed from a viewpoint of the amount of lubricant on the disk.Exoerimental m e disk was 3.5" particulate recording disk which has magnetic upper layers (0.2nm) and nonmagnetic under layers (1.5um) on botb sides of PET (62bt1). The-surfaie roughnes-Ra of the disk was approximately 4nm. Alkyl carboxylate was incorporated as lubricant into the disk-A. Moreover, it was coated by the spin-coater with concentration of 5 and 8 wt% toluene solution on the disk-A, respectively (disk-B and disk-C). The friction force was measured by the difference in the motor current before and after the head loading. Relative friction force was normalized by the value of the diskB at 13.2 m/s. Relative velocity was changed by the disk rotation speed while head position has been kept.Results and Dlscussion Figure 1 shows relative velocity dependence of friction force as coating lubricant on the disk-A. Friction force of disk-A decreased with increasing relative velocity. Friction force of diskB was steady in low value when relative velocity was faster than 4.4m/s. The friction of the disk-C was always higher than that of the disk-B. In less than 4.4m/s, the relative friction force exceeded 22 and the head began to creak. Figure 2 shows friction force of 13.2ds versus concentration of the applied toluene solution with the lubricant. The friction force decreased gradually with concentration, and increased rapidly in the concentration around the 8wt%. The amount of surface lubricant will be discussed.From these results, applying lubricant to the disk-A, the friction force decreases gradually and is steady in a low value over a certain relative velocity, that is, the condition of head flying is almost reached. However, as the lubricant exceeds a proper amount, the contact between the head and the disk occurs again. It is considered that it is due to the appearance of the meniscus by excess lubricant. Magn. Magn.Mater., to be published. 0 0 2.2 4.4 6.6 R d I1 1 3 2 15.4 ( -1 ( I l m r n )