Hot embossing of grating-based optically variable images in thermoplastic acrylic lacquer
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We report the novel use of thermoplastic acrylic lacquer (automotive paint) in the hot embossing of nanoscale structures. Replicas of grating arrays have been produced in coatings of acrylic lacquer using a standard embossing process. The master dies for the experiments comprised grating arrays fabricated by electron beam lithography. Grating patterns with a pitch of 0.7–1.3 μm were configured to produce diffractive images over an area of ∼25 × 25 mm. The embossing experiments used a replicated Ni shim as a die and were performed at 100–150 °C and 80 kN force. A temperature above the glass transition temperature for the lacquer, T = 120–150 °C, was required in order to achieve a uniform impression across the embossed area of ∼80 × 80 mm. The diffractive grating patterns which were embossed into acrylic lacquer have shown optical effects suitable as a security feature including image switching and color movement.
KeywordsDiffraction Efficiency Electron Beam Lithography Diffractive Image Emboss Process Master Image
E-beam lithography was performed by R. Marnock and nickel shims were produced by F. Glenn.
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