Appeal No. 2002-0912 Page 6
Application No. 08/913,187
sliding contact with the workpiece be “coated with a hard carbon film . . . formed on an
intermediate layer formed on the inner surface to enhance the adhesion of the hard
carbon film to the inner surface.”
Toshimitsu is directed to a hydrodynamic bearing for spindle and drum motors in
data storage devices. The reference states that in order to provide high resistance to
wear, the sliding surfaces of these bearings are made of metallic material coated with a
film of ceramic material such as silicon carbide, silicon nitride, alumina and the like. A
thin film of liquid lubricant can be interposed between the sliding surfaces, by means of
a plurality of grooves in the sliding surface. See columns 1 and 2. To improve the
coefficient of friction of these bearings, Toshimitsu teaches coating the sliding surface
with a uniform hydrogenated amorphous film (column 8, lines 35-40), which is the same
material disclosed by the appellants as the “hard carbon film” recited in their claims
(specification, page 2). Toshimitsu explains that if the sliding surfaces are made of a
ceramic material there is good adherence between the sliding surface and the
hydrogenated amorphous film deposited thereon, but
[i]f the sliding surfaces are made of a metallic material, its coefficient of
linear expansion is widely different from that of the hydrogenated
amorphous carbon film. Therefore, cracks may produce in the
hydrogenated amorphous carbon film due to residual internal stresses
developed due to an increase in the temperature rise of the sliding
surfaces during the deposition of the hydrogenated amorphous carbon
film. To avoid such a defect, the sliding surfaces may be coated with the
ceramic material, referred to above, and then a hydrogenated amorphous
carbon film may be deposited on the coated sliding surfaces. In this
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