Provision of frames or borders around pigment flakes for covert security applications

摘要

Opaque flakes, such as pigment or bright flakes used in paints and inks, have a selected shape and/or other indicia to provide a covert security feature to an object. Shaped opaque covert flakes are not readily detectable by causal observation, but in some embodiments are easily seen at 50× magnification. In manufacturing the flakes a sheet of embossed frames are provided having embossed symbols or indicia within. Upon removing a coating from the embossed sheet the coating material tends to break along frame lines or grooves and the resulting flakes are substantially uniform in size. In order to have the flakes break along frame lines or grooves more readily than along the embossing or grooves defining indicia within a frame, the frames are provided with a deeper groove than indicia grooves. As well a groove having a different shaped profile conducive to breakage can be used for the frame grooves whereas a groove having a profile less conducive to breakage can be used to form the indicia grooves. We have found that the flakes can be further protected from breakage by coating them in a protective coating. This coating may have other features which makes the logo more visible.

主权项

1. A plurality of pigment taggent flakes, each flake having
a first surface; an indicia defined by one or more regions having a second surface extending in a first direction with respect to the first surface to a maximum distance Id from the first surface, and a frame defined by one or more walls disposed at a periphery of the flake so as to at least partially surround the indicia, each wall extending in the first direction to a distance of at least Fh from the first surface, where Fh>Id.