Measurement of Friction Coefficients between Diamond-like Carbon VCR Head Drum and VCR Tapes

 In order to characterize friction and wear behavior between cylindrical specimens and flexible counterface materials such as magnetic tape, a tribometer is suggested. The tribometer is used to investigate the behavior between video cassette recorder (VCR) head drums and VCR tapes. Friction coefficients of uncoated and diamond-like carbon (DLC) film coated head drums of Al alloy are compared before and after a wear test. Before the wear test, an uncoated head drum shows friction coefficients ranging from 0.22 to 0.3 as the applied tension increases from 200 to 600 gf at the sliding speed of 0.16m/s. The friction coefficients of DLC coated head drum are 14 to 30% lower than those of uncoated head drums. At the sliding speed of 4.9m/s, the friction coefficients of both uncoated and DLC coated head drums are reduced to less than 0.1. After the wear test, however, the friction coefficients of uncoated head drums increase to the range from 0.3 and 0.47 depending on the applied tensions. Furthermore, the friction coefficients are not reduced even at the high sliding speed of 4.9m/s. DLC coated head drums, on the other hand, exhibit similar friction coefficients to those before the wear test. Degradation of frictional property in the uncoated head drum is discussed in terms of the surface damages mainly due to magnetic metal oxide particles transferred from VCR tapes. This result shown that the DLC coating of VCR head drum can improve the friction and wear properties. It is also observed that the DLC coating can reduce the damage of VCR tapes.