| 摘要 |
A tamper evident security film in particular for use as a tamper-evident tape comprises a polymer substrate film 10, e.g. of HDPE, and a layer of coloured contrast agent (38, Fig. 3) adhered to the surface of the film. The adherence between the colored contrast layer and the substrate film is modified by selective plasma treatment, e.g. by corona discharge, of the substrate film to create a pattern of adhered regions, having strong adherence, and intervening regions having weak adherence. The substrate film may be plasma treated by passing the film over a patterned roller 6 which has a conductive external surface 14, the pattern, either in relief (Fig. 1a) or cut (Fig. 1b), constituting an array of indicia such as the word "VOID". The roller surface may be a layer of conductive polymer, laser cut to make the pattern. No plasma forms on the outer surface in pattern regions where the roller surface 14 is recessed, so a subsequently applied coloured contrast layer, e.g. polymeric ink, adheres poorly in those regions. An adhesive layer (44, Fig. 3) and protective release layer (46, Fig. 3) are applied over the ink layer. |
