Believe it or not, a label’s ability to provide security is directly related to the self-adhesive that’s being used. Basically, a self-adhesive is a chemical fastening system that isn’t heat-activated or activated by the evaporation of a solvent. Rather, the self-adhesive is activated by the application of pressure. It is only through the strength of an adhesive that the other elements of security labels like the substrate, seal or lamination on a label can be deemed effective.
Today’s adhesives, thanks to modern chemistry are able to provide labels with all of the needed properties for the increase and maintenance of security. But adhesives go beyond simply applying a label to a surface; adhesives can also be used to achieve certain label properties.
Opacity vs. Transparency
When an adhesive is loaded with aluminium powder, and then opaque materials are selected such as metallised film, opacity is achieved. It can also be achieved by printing labels using a single or series of particular printing processes.
Transparency is actually the more difficult property to achieve. There is a high demand for transparent labels, especially for ‘invisible’ style labels. Where ever the protection of documents, photographs or other security label elements is required, testing must occur beyond the lab.
Elements of Transparency Testing
Of course, the testing of any adhesive should occur in the laboratory. But even if real-world conditions can be replicated in a laboratory, real-world testing should also occur. For example, if a security label is supposed to adhere to a vehicle’s window, the fact that it will be exposed to all intensities of light and temperature should definitely be considered.
But in addition to that, it’s the fact that light and intensity will affect the label on both sides. A vehicle’s interior temperature can vary greatly from the temperature outside the vehicle. And a label’s temperature on the outer-facing side may also vary greatly on its inner-facing side.
The ability of a transparent label to be repositioned is another element that needs to be considered. As well, a label’s ability to be repositioned can also be affected by both internal and external temperatures. However, the client’s needs must also be thought of. If a client requires their labels to be permanently affixed, this will require a different set of properties than a client needing a highly-repositionable label.
Materials being adhered to
Understandably, there is a level of concern with regard to the potential damage of surfaces that labels are being adhered to. Indeed, there are several potential complications, especially where a label needs to be affixed to a wide range of surfaces.
Clarity of Transparency
Currently, the material offering the most clarity in terms of transparent films is PET or polyester. After this, it’s polypropylene, polystyrene and polyethylene. But of course, a high degree of transparency must ensure that both the label and its adhesive are equally transparent.
Most transparent adhesives are a minimum of 10 microns thick. They are usually applied in coats of around 20 grams per square metre. Even with adhesives, care needs to be taken to ensure that any backing used to protect the self-adhesive will not damage the adhesive when removed or if left to sit for long periods of time.
The removal of any self-adhesive label by a thief can be prevented by ensuring that the adhesive being used is able to resist the efforts by the thief to breach the adhesive bond. As well, any attempts to remove the label should be accompanied by some form of visual clue that the label has been tampered with. And although it may not be the most desirable measure, attempts to remove a label can also be made evident on the surface where the label is affixed.