Improvements of tribological properties of metal evaporated tapes for Digital recording by DLC protective coating

Hiroyuki Osaki

Sony Corporation, Sendai Technology Center, 3-4-1 Sakuragi, Tagajo, Miyagi 985-0842, Japan

E-mail:Hiroyuki.Osaki@jp.sony.com, TEL:81-22-367-2452, FAX:81-22-367-2589

Abstract

With the increase in the recording density of hard disk systems, the demand on the increase in the data recording capacity of removal cassettes of tape drive systems as back-up systems for hard disk systems which could cause “head crash” trouble is increasing. One of the advantages of the tape drive systems is high volumetric recording density, which is obtained by high areal recording density and thin tapes. The areal recording density can be increased by introducing high performance tapes, such as metal evaporated tapes with superior magnetic characteristics and smooth surface. Smooth surface produces higher friction coefficient, which could cause tape damage by rotary heads and unstable tape runnability in the tape drives. The durability and runnabiity of the metal evaporated tapes had been improved by forming surface asperities on it to reduce the friction by decreasing real contact area, sacrificing recording characteristics a little by spacing loss between tape and magnetic heads. However, the height of surface asperities of metal evaporated tapes should be reduced to achieve higher areal recording density for increasing demand.

The decrease in the height of surface asperities results in the short life time until they are worn out. Therefore, the wear resistant coating is required to keep the initial height of low surface asperities even after many rubbing cycles. The thickness of wear resistant coating should be less than ten nanometers to reduce the total spacing loss produced by the height of surface asperities and the thickness of wear resistant coating. It was found that the combination of DLC (Diamond like Carbon) coating and a lubricant is very effective. Even after a hundred million head traces, the wear of surface asperities could not be observed. By this combination, metal evaporated tapes have obtained superior durabilities, as well as superior recording characteristics, as the tapes for data storage systems and digital video systems.

Keywords: tape drive systems, metal evaporated tape, surface asperities, wear resistant coatings, DLC