Security document and system
AssigneeE M I Limited
InventorCyril A. Lee
Life of this patent
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Abstract
A magnetizable anisotropic material layer having a pattern of regions of differently aligned material has an initial pattern of remanent magnetization, when manufactured by applying directional magnetic fields. This pattern is not easily restored, and is generally impossible to restore, after demagnetization or remagnetization. By preserving the residual pattern and selectively removing it in use by the application of a magnetic field, a security feature is provided. A secure document system using such a feature is provided.
Claims10
A secure document system comprising a secure document having a security feature of which at least a part is selectively cancellable, and apparatus for performing the cancellation,
- wherein in spaced first regions of said selectively cancellable part anisotropic magnetic particles are aligned and magnetised substantially solely along a preset direction and in the remaining regions of the part the particles are either not so aligned or are aligned and magnetised substantially solely along a different preset direction, and said apparatus comprises means for reading at least said part and means for cancelling a selected area, which cancelling means applies a uniaxial magnetic field to said area of such a strength and direction that the difference in remanence between said first regions and said remaining regions is significantly reduced.
Dependencies are inferred from the claim text.