Security films and manufacture thereof

A security film laminate, comprising

• a polymeric substrate film, said substrate film having a first surface and a second surface;
• a layer of coloured contrast agent adhered to the first surface of the substrate film, the substrate film and layer of coloured contrast agent having a mutual contact interface;
• the contact interface having a pattern of adhered regions and intervening regions, said pattern being in the form of a repeating array of indicia selected from letters, words, numbers and symbols, and the adhesion between the contrast agent layer and the substrate film being stronger at the adhered regions than at the intervening regions, the substrate film having been plasma-treated in said pattern, at regions corresponding to the adhered regions, to increase the surface energy before application of said coloured contrast agent layer thereto;
• an adhesive layer superimposed over the contrast agent layer, and
• a release layer superimposed in contact over the adhesive layer, to be peeled away for use of the film laminate.

A method of making a security film laminate comprising

• a polymeric substrate film, said substrate film having a first surface and a second surface, and
• a layer of coloured contrast agent adhered to the first surface of the substrate film, the substrate film and layer of coloured contrast agent having a mutual contact interface;
• the method comprising the steps of:
• (i) placing the polymeric substrate film for treatment in a corona discharge treater having a support electrode and a treater electrode, the support electrode having a treatment surface against which said second surface of the film rests, the electrode treatment surface having support regions which contact the second surface of the film to support it and relatively recessed regions where there is a gap between the second surface of the film and the treatment surface, said support regions and relatively recessed regions defining a pattern;
• (ii) producing plasma between the treater electrode and the support electrode, whereby on the first surface of the film plasma forms only above said support regions, thereby plasma treating said first surface of the film according to said pattern to increase the surface energy thereof in regions according to said pattern;
• (iii) forming said contrast agent layer on the first surface of the polymeric substrate film, whereby adhesion between the contrast agent layer and the substrate film is stronger at the film regions plasma treated according to said pattern, and corresponding to said support regions of the electrode treatment surface, than at intervening regions corresponding to said relatively recessed regions of the electrode treatment surface.