Watermark and other security features for thermoplastic security documents

#This application is a U.S. National Stage of PCT/CA2017/050452, filed Apr. 12, 2017, which claims priority of Canadian Patent Application No. 2,927,176, filed Apr. 15, 2016, each of which is incorporated herein by reference.

#The present invention relates generally to security documents. In particular, the present invention relates to new and improved methods for creating watermarks and other security features comprising micro-structures embedded within security documents comprised of laminated layers of thermoplastic, for example, identification (ID) documents, driver's licenses, passports, and banknotes.

#The use of watermarks is known in the prior art. EP1518661B1 discloses a process which involves the softening of the polymer by electromagnetic radiation followed by stretching to create opacity differences within the substrate. The cost of the equipment for this process is high and since the polymer is laser ablated, toxic fumes are generated and need to be extracted. This leads to an expensive process for utilizing this method for producing a watermark.

#FIG. 1 is a schematic illustration of the first lamination step of a method for producing a watermark using an embossed plate to emboss an opaque polycarbonate sheet whereby the negative image on the plate creates a positive deformation or embossment on the white sheet.

#FIG. 2 is a schematic illustration of the second lamination step whereby layered polycarbonate films are placed between two lamination plates, and pressed at high temperature and pressure to fuse together and form a monolithic card, and the embossment created by the first lamination step is sustained after lamination.

#FIG. 3 is a schematic Illustration of a finished generic polycarbonate card construction, e.g. an ID card, wherein a white polycarbonate sheet is located between two clear polycarbonate sheets.

#As detailed below the present invention provides security features formed and/or arranged by micro-structures within multilayer laminate security documents by embossing and/or debossing one or more thermoplastic layers prior to lamination of the layers.

#1. Watermark

#An identification card is made up of a plurality of layers, including a white opacified layer in the middle layer that has been altered to comprise a watermark providing varying shades when viewed under transmitted light. To create a watermark by the method described herein a displacement of the opacified material is established using a lamination plate. The first lamination step, illustrated by FIG. 1, is completed prior to the second lamination step, illustrated by FIG. 2, of laminating together the multiple polycarbonate layers of the ID document. That is, a white opacified layer is altered by the first lamination step before that layer is laminated with other layers by the second lamination step to form the ID document. The so altered opacified layer is positioned in the interior or middle of the ID document where it is enclosed with clear layers of sheets on both sides. The displacement of the material of the opaque layer by means of the first lamination step can be done on an at least 25 um polycarbonate sheet using an embossed plate. The variation in optical transparency to result from the first lamination step can be determined by the thickness of the embossments on the plate.