Patent GB-1334689-A (GB)
Title: Tamper proof label construction
IPC: B42D11/00
Filed: 1970-10-26
Abstract: 1334689 Laminated labels AVERY PRODUCTS CORP 26 Oct 1970 [27 Oct 1969] 50717/70 Heading B5N A composite tamper-proof label comprises an at least partially transparent self-supporting film, e.g. of ethylene or propylene polymers or copolymers, acrylic polymers, polyvinyl acetate, chloride or fluoride, cellulose acetate, polycarbonates, polyethers, polysulphones or polystyrene, having visual indicia imprinted on at least one surface of a transparent portion thereof and an adjesive layer having a first adhesive surface in contact with said surface of the transparent portion of the self-supporting film and a second adhesive surface for contact with a substrate, the arrangement being such that an attempted removal of the label from a substrate to which it has been applied, predetermined selective removal from the substrate occurs of a portion of the total visual indicia while the other of the indicia and at least a portion of the adhesive layer remain on the substrate. The predetermined selective removal may be provided by means of a masking layer extending selectively over the said surface of the transparent portion of the self-supporting film, the first adhesive surface being in contact with the masking layer and with the film and the masking layer being applied over a portion of the indicia on the film or the indicia being applied over the film and the masking layer, the masking layer having limited adhesivity to the film or to the first adhesive surface and the first adhesive surface having a greater adhesivity for the indicia on the unmasked portion of the film than the adhesivity of the indicia for the transparent film. Alternatively, the predetermined selective removal may be provided by a portion of the self supporting film being treated to alter the adhesive properties thereof, e.g. flame or corona treated polyethylene, so that the adhesivity of indicia in contact with the untreated portion of the film is less than their adhesivity for the first adhesive surface and the adhesivity of the balance of the indicia for the treated portion of the film is greater than their adhesivity for the first adhesive surface. The surface of the transparent film remote from the masking may be in selective contact with a second masking layer, one at least partially transparent printable overlayer and an at least partially transparent protective film, the adhesivity of the protective film for the overlayer being greater than the maximum interlayer adhesive band in the laminate comprising the overlayer, the second masking layer and the self-supporting film but less than the adhesivity of the overlayer for the self-supporting film or greater than the adhesivity of the overlayer for the self-supporting film but less than the adhesivity of overlayer for the second masking layer and of the second masking layer for the self-supporting film. The masking layer may be a self-supporting film or transparent printable ink of nitrocellulose, chlorinated rubber, acrylic polymers or polyamides, the adhesive layer may be a laminate of two or more adhesives, or a single layer of solvent, moisture or heat activated adhesive or pressure sensitive adhesive covered with a release coated paper. Label stock comprises as first component the self-supporting film having a transparent masking layer extending selectively over portions thereof and as a second component the adhesive layer.