A Glass Disk Structure with Improved Thermal Erasure
Original Publication Date: 2000-Apr-01
Included in the Prior Art Database: 2003-Jun-20
Described is a glass disk structure for thermal erasure improvement. This disk structure consists of a thermal conducting layer and a seed layer as well as underlayer\magnetic layer\overcoat\lubrication layer. The function of the thermal conducting layer, such as CrV, Si, Cu, and Ag, is to conduct the heat generated due to head disk contact or particles/contamination fast enough to prevent thermal erasure of written data. The role of the seed layer is to ensure the epitaxtial growth of the sequentially deposited layers so that high recording density can be achieved. Thermal erasure occurs whenever the temperature of the magnetic layer of a hard disk is higher than its Curie temperature. The thermal conductivity 0.76 W/mC) of glass substrates currently in use is much lower than that of AlMg substrates (280 W/mC). Thus heat induced due to head-disk interaction , such as contacting of the slider corner with the disk surfaces and head particles dragging on the disk surfaces, could raise the magnetic temperature higher than its Curie temperature and consequently erase previously written data. This temperature rise of the magnetic layer could be reduced significantly with the deposition of a high thermal conducting layer on the glass substrates. Experimental results show that CrV, Si, Cu, and Ag thermal conducting layers serve this purpose well (Fig. 1). On the other hand, those sputter deposited thermal conducting layers are polycrystalline and have their own crystallographic texture that may in turn induce undesirable epitaxial growth and large grain size of the sequentially deposited layers. Therefore, bulk magnetic and recording properties deteriorates by only using the thermal conducting layer. Thus a seed layer deposited on the thermal conducting layer is needed to ensure the magnetic and recording properties of the disk. Figure 2 shows this invented disk structure schematically. 1 Fig.1 Optic images of the ferrofluided surfaces of glass disks (a) without a Cu thermal conducting layer and (b) with a Cu thermal conducting layer.