In the adherent coating of polymethyl methacrylate substrates by cathodic sputtering, the sputtering gas (pref. Ar) is mixed with a hydrocarbon-contg. additive gas (pref. methane or an alcohol-contg. gas) which affects the substrate surface during sputtering to promote intimate bonding of the sputtered cathode material (pref. a silvery metal, esp. Al) to the substrate. The sputtering gas pref. contains max. 50 vol.% additive gas. The sputtering vessel housing forms the anode and is made of an electrically conductive material, pref. copper. USE/ADVANTAGE - Useful in the mfr. of optical data carriers such as compact discs or video discs. It allows adherent metallisation of acrylic glass substrates in a single step, without requiring special substrate pretreatment, by a quasi-continuous prodn. process.
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