Security elements and method of manufacture thereof

Abstract

A security element including: a first layer having a first surface; an array of image regions across the surface, each including at least first and second sub-regions; a first array of plasmonic nanostructures in or on the surface across the first sub-regions, defining in each a corresponding portion of a first image; a second array across the second sub-regions, defining in each a corresponding portion of a second image; wherein each sub-region has a respective average inclination and the average inclinations of the first sub-regions are such that the first image is displayed at least at a first viewing angle and those of the second sub-regions are such that the second image is displayed at least at a second viewing angle different from the first and the second image is substantially not or only partially displayed at least at the first angle. Also, a method of manufacturing the security element.

Description

FIELD OF THE INVENTION[0001]The present invention relates to security elements such as those suitable for use in or on security documents such as banknotes, identity documents, passports, certificates and the like, as well as methods for manufacturing such security elements.DESCRIPTION OF THE RELATED ART[0002]To prevent counterfeiting and enable authenticity to be checked, security documents are typically provided with one or more security elements which are difficult or impossible to replicate accurately with commonly available means, particularly photocopiers, scanners or commercial printers.[0003]Many conventional security elements utilise optically variable effects, i.e. an appearance that changes upon rotation of the device, which cannot be replicated by copying, as with a photocopier or scanner. One class of optically variable security elements includes those that utilise diffractive optically variable effect generating relief structures, such as diffraction gratings, to gener...

AI Technical Summary

Benefits of technology

The present structure described in this patent allows for the display to show different images at different viewing angles. By using plasmonic nanostructures, the device can present a series of images to a viewer by tilting the device. The arrangement of the nanostructures can show different perspectives of an object, and the viewer's perspective can change when they change the object being depicted in the images. The images can be freely configured and the viewer's perspective can control the appearance of the images. The plasmonic nanostructures can vary in shape, size, and spacing across different sub-regions, which affects the color generated by each region. This allows for the creation of full-colour images with integrated registration between the colors.

Problems solved by technology

In contrast, processes that use printed inks in generating an optically variable effect, e.g. security elements that use printed image elements in combination with focussing elements, often suffer from misregistration between different colours since they are typically printed in separate print processes.

Security elements that utilise diffractive optically variable effect generating relief structures suffer from the problem that, when viewed under diffuse lighting conditions, as is typical, the security element can appear noisy as diffraction conditions for multiple structures are satisfied simultaneously.

Images