Sharper Edges, Stronger Security: Inside Demax’s FreeEdge™ Innovation

Diffractive optically variable image devices (DOVIDs) are widely used to protect documents against counterfeiting and misuse. They are commonly integrated into multilayer holographic foils, which are either hot-stamped onto documents such as credit cards, driving licenses, identity cards, passports, and banknotes or embedded into laminates that are heat-sealed to a document’s surface.

A well-known drawback of traditional multilayer foils, however, is their incompatibility with porous or rough document surfaces, such as the paper pages of passports or banknotes. Applying these foils requires a relatively thick adhesive layer, which often leaves unwanted foil residues at the edges of the stamped area. During the application process, the embossing layer can tear at these boundaries.

If a thinner adhesive layer is used on rough surfaces, adhesion is often insufficient, as the foil only bonds to the protruding parts of the substrate texture. Conversely, with a thick adhesive layer, the diffraction pattern itself can be degraded. Thermal and mechanical stress may damage the holographic structures, leading to a faded appearance where the image loses brightness and becomes pale or matte.