Abstract

AbstractDiffractive grating structures formed by electron beam lithography have been replicated into the surface of silver commemorative coins. The detailed features of the gratings and the depth of relief were accurately transferred from the resist master plate to the surface of the fine silver coins using a Ni shim as a replication tool. This method has produced an optically variable device (OVD) in the surface of the coins which exhibited a strong intensity of first order diffraction over the area of the image (3 × 1.5 cm). A feature of the grating structures formed in the coins were fine-scale protrusions located along the length of the ridges. The presence of these protrusions has been attributed to an adhesive transfer and back-transfer of Ag during the cycle of impact loading of the Ni shim for sequential coins.

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