OPTICAL EFFECT LAYERS SHOWING A VIEWING ANGLE DEPENDENT OPTICAL EFFECT, PROCESSES AND DEVICES FOR THEIR PRODUCTION, ITEMS CARRYING AN OPTICAL EFFECT LAYER, AND USES THEREOF

摘要

The invention relates to the field of the protection of security documents such as for example banknotes and identity documents against counterfeit and illegal reproduction. In particular, the invention relates to optical effect layers (OEL) showing a viewing-angle dependent optical effect, devices and processes for producing said OEL and items carrying said OEL, as well as uses of said optical effect layers as an anti-counterfeit means on documents. The OEL comprises a plurality of non-spherical magnetic or magnetizable particles, which are dispersed in a coating composition comprising a binder material, the OEL comprising two or more loop-shaped areas, being nested around a common central area that is surrounded by the innermost loop-shaped area, wherein, in each of the loop-shaped areas, at least a part of the plurality of non-spherical magnetic or magnetizable particles are oriented such that, in a cross-section perpendicular to the OEL layer and extending from the centre of the central area to the outer boundary of the outermost loop-shaped area, the longest axis of the particles in each of the cross-sectional areas of the looped-shaped areas follow a tangent of either a negatively curved or a positively curved part of hypothetical ellipses or circles.

主权项

1. An optical effect layer (OEL) comprising a plurality of non-spherical magnetic or magnetizable particles, wherein at least a part of the plurality of non-spherical magnetic or magnetizable particles is constituted by non-spherical optically variable magnetic or magnetizable pigments, and wherein the non-spherical magnetic or magnetizable particles are dispersed in a coating composition comprising a binder material,
the OEL comprising two or more loop-shaped areas, being nested around a common central area that is surrounded by the innermost loop-shaped area, wherein, in each of the loop-shaped areas, at least a part of the plurality of non-spherical magnetic or magnetizable particles are oriented such that, in a cross-section perpendicular to the OEL layer and extending from the centre of the central area to the outer boundary of the outermost loop-shaped area, the longest axis of the particles in each of the cross-sectional areas of the looped-shaped areas follow a tangent of either a negatively curved or a positively curved part of hypothetical ellipses or circles.