"Dual-carbon", a new surface protective film for thin film hard disks

The surface protective layer for wear resistance of CoNiCr/Cr sputtered hard disk has been studied. The carbon film continuously sputtered on CoNiCr/Cr disk has a good wear resistance against a Mn-Zn ferrite head slider but not against CaTiO3and Al2O3-TiC head sliders. The P-CVD carbon film prepared by the RF or DC discharge of C2H2gas on a CoNiCr/Cr disk is also not good. The P-CVD carbon film deposited at low C2H2gas pressure is sufficiently hard but the friction coefficient is too large, while the film deposited at high pressure has contrarily small friction coefficient and the small hardness. The double layer film of the P-CVD carbon layer deposited at higher pressure on the sputtered carbon layer or P-CVD carbon layer deposited at lower acetylene gas pressure has both of the good wear resistance and the small friction coefficient even against to CaTiO3and Al2O3-TiC head sliders. We call this double layer film newly designed as the "DUAL CARBON".