Printed security mark for e.g. banknotes has a latent intaglio image of strongly-reflecting ink visible from certain angles and giving a flickering effect, optionally together with a non-intaglio image

摘要

A printed security mark for a document has a latent intaglio printed image with a strongly-reflecting ink, the image being visible from a first angle close to the perpendicular and also from a second angle nearer to the image plane but not visible from an angle in-between so that by altering the viewing angle the latent image switches from visible to invisible or vice-versa.