| 摘要 |
An ultraviolet (UV) radiation-curable temporarily pressure sensitive composition which when irradiated with ultraviolet light quickly attains a high tack state for transferring dielectric material thereto, and within hours permanently bonds to the dielectric material to form a thin film security device (TFSD). The UV radiation-curable pressure sensitive adhesive comprises, in one aspect: (a) at least one saturated copolyester having terminal acrylic double bonds and hydroxyl moieties; (b) at least one pigment dispersed in a liquid selected from the group consisting of an acrylic monomer, a vinyl ether monomer, oligomers thereof, and blends thereof; (c) at least one vinyl ether monomer, oligomers thereof, or blends of said vinyl ether monomer and oligomers; and (d) at least one photoinitiator in a quantity sufficient to render the composition tacky within about 1 second after exposure to ultraviolet radiation. In another aspect the UV radiation-curable temporarily-pressure-sensitive adhesive is as described above with the exception that it is "clear", i.e. contains no pigment. The invention also provides a method of providing a substrate (and more specifically, banknote paper) with indicia, which comprises: (1) forming a laminate of (a) a polyester film having a thickness of 12-25 microns, (b) a release coating of a thickness of 1-2 microns, (c) a protective layer 1-2 microns thick, and (d) a stack of dielectric and/or metal layers having a maximum thickness of 1 micron; (2) providing a plurality of areas on the substrate, each of which areas bear a UV-curable pressure-sensitive adhesive as described above; (3) sujecting the substrate containing the aforesaid adhesive-bearing areas to UV radiation to cause the areas to become highly tacky; (4) bringing the outer surface of the stack of dielectric and/or metal layers into pressurized contact with the adhesive-bearing areas on the substrate, thereby adhering the laminate to the adhesive-bearing areas on the substrate; and (5) stripping the laminate away from the substrate, whereby the dielectric and/or metal layers are sheared from the release coating and firmly adhere to said adhesive-bearing areas on the substrate. |
