The application of ion plating to the continuous coating of flexible plastic sheet

Abstract

Ion plating onto plastic substrates was demonstrated to give considerable advantages in that adhesion is increased and properties can be obtained which would normally require higher temperatures than the substrate is capable of withstanding. In order to coat large areas of sheet plastic it is necessary to achieve high deposition rates without creating high substrate temperatures. This is done in commercial apparatus by pulling the sheet substrate tightly over a very smooth cooled drum and transferring the plastic from an initial roll to a final roll over this rotating drum. Conventional resistance-heated sources are generally used, though induction and electron beam heating have also been applied. Simple diode sputtering results in damage to the plastic from both heat and electron bombardment. This can be avoided if a planar magnetron source is used. We created an apparatus which allows plastic sheet passing over a rotating drum to be subjected to an r.f. discharge either before, or simultaneously with, the deposition of material from a planar magnetron source. The material may be deposited directly from the source, or reactive processes may be used with carefully chosen reactive gas inlet points. The r.f. power is applied to the roll, which is isolated by carefully designed insulation techniques whereby the storage rolls and the drum are mounted within an r.f. cage. All motor drive shafts are insulated and only the surface of the drum over which the plastic is rolled is exposed to the general chamber; the rest of the apparatus is protected by a closely spaced earth shield. The results of experiments using planar magnetron sputtering sources, including the successful use of ion plating to give transparent conducting oxide films of In-10%Sn onto flexible plastic sheet, are given.