Security devices and methods of manufacture thereof

• Main Authors: Rebecca Locke, John Godfrey
• Format: Patent
• Language: English
• Published: 04.09.2024
• Subjects: BOOK COVERS; BOOKBINDING; COLOUR PRINTING; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDEDFOR; FILES; LINING MACHINES; LOOSE LEAVES; MOVABLE-STRIP WRITING OR READING APPARATUS; PERFORMING OPERATIONS; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITYFEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOTOTHERWISE PROVIDED FOR; PRINTING; PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; SPECIAL PRINTED MATTER; STAMPS; TRANSPORTING; TYPEWRITERS

An optically variable security device 110 comprises a substrate 10; an array of focussing elements 20 disposed; and an image array 30 overlapping with the array of focussing elements. The focussing elements and the image array cooperate with each other such that at first and second ranges of viewing angles respective images A, B are exhibited to the viewer. The image array comprises different first and second inks. One or both of the first and second inks comprises a luminescent material which luminesces in response to irradiation at least one excitation wavelength. The first and second inks each exhibit a respective non-luminescent visible colour when illuminated with a first illumination condition that comprises illumination with visible light in the absence of the at least one excitation wavelength, and one or both of the first and second inks exhibit a visible colour when illuminated with a second illumination condition that comprises illumination with the at least one excitation wavelength. The first and second inks exhibits a different visual appearance when illuminated with the first illumination condition compared to when illuminated with the second illumination condition.