| abstract |
A barrier coating against oxygen and water vapor penetration for a plastic packaging film comprising two oxides, one of which is SiO 2 while the other is Al 2 O 3 . The barrier is a single layer of mixed oxides in which the concentration of Al 2 O 3 increases continuously from 20% by weight to 80% by weight while the concentration of SiO 2 decreases continuously from 80% by weight to 20% by weight as the thickness of the mixed oxide layer increases from the surface of the plastic film. The plastic film is preferably polyethylene terephthalate or polyphenylene oxide and the barrier coating is transparent. |