Paired optically variable security element
AssigneeSicpa Holding SA
InventorsAnton Bleikolm, Pierre Degott, Edgar Mueller
Life of this patent
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Abstract
Disclosed is a paired optically variable security element which comprises first and second optically variable thin-film multilayer interference devices in the form of optically variable foils or of printings made with inks comprising optically variable interference pigments, wherein said first and second interference devices exhibit spectral matching at a determined angle of incidence. Sets of optically variable devices and of coating compositions comprising optically variable pigments for the production of said paired optically variable security element are also disclosed, as well as the use of said security element for the protection of documents and goods, and security documents and goods carrying same.
Claims16
-18. (canceled)
Paired optically variable security element, comprising a first optically variable interference device having a first dielectric of a lower refractive index (nlow), and whose kth-order reflection maximum (k) shows a shift from a first reflection wavelength (λ1) at orthogonal incidence to a second, shorter wavelength (λ2) at grazing incidence, and a second optically variable interference device having a second dielectric of a higher refractive index (nhigh), and whose same kth-order reflection maximum (k) shows a shift from a third reflection wavelength (λ3) at orthogonal incidence to a fourth, shorter wavelength (λ4) at grazing incidence, wherein the first and the second optically variable interference devices are arranged such that they can be viewed together, characterized in that
- the range spanned up by said third and said fourth wavelengths of said second device is within the range spanned up by said first and said second wavelengths of said first device, and in that the first and the second optically variable interference devices have a same, particularly quarter-wave or half-wave, interference design at the angle of incidence of spectral matching.
Process for making a paired optically variable security element, comprising the steps of
- a) applying to a substrate (S) a first optically variable interference device having a first dielectric of a lower refractive index (nlow) and whose kth-order reflection maximum (k) shows a shift from a first reflection wavelength (λ1) at orthogonal incidence to a second, shorter wavelength (λ2) at grazing incidence;
- b) applying to said substrate (S) a second optically variable interference device having a second dielectric of a higher refractive index (nhigh), and whose same kth-order reflection maximum (k) shows a shift from a third reflection wavelength (λ3) at orthogonal incidence to a fourth, shorter wavelength (λ4) at grazing incidence;
- wherein the first and second optically variable interference devices are arranged such that they can be viewed together;
- characterized in that the range spanned up by said third and said fourth wavelengths of said second device is within the range spanned up by said first and said second wavelengths of said first device,
- and that the first and second optically variable interference devices have a same, particularly quarter-wave or half-wave, interference design at the angle of incidence of spectral matching.
Dependencies are inferred from the claim text.