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

Patent metadata

Field	Value
Publication number	US-9724956-B2
Application number	US-201414759831-A
Country	US
Kind code	B2
Filing date	Jan 7, 2014
Priority date	Jan 9, 2013
Publication date	Aug 8, 2017
Grant date	Aug 8, 2017

Abstract

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, wherein in at least a loop-shaped area of the OEL at least a part of the plurality of non-spherical magnetic or magnetizable particles are oriented such that their longest axis is substantially parallel to the plane of the OEL, and wherein, in a cross-section perpendicular to the OEL and extending from the center of the central area, the longest axis of the oriented particles present in the loop-shaped area forming the impression of the loop-shaped body follow a tangent of either a negatively curved or a positively curved part of a hypothetical ellipse or circle.

First claim

The invention claimed is:

1. An optical effect layer (OEL) comprising:
a plurality of non-spherical magnetic or magnetizable particles, which are dispersed in a coating composition comprising a binder material,
wherein in at least a loop-shaped area of the OEL at least a part of the plurality of non-spherical magnetic or magnetizable particles are oriented such that their longest axis is substantially parallel to the plane of the OEL, and wherein, in a cross-section perpendicular to the OEL and extending from the center of the central area, the longest axis of the oriented particles present in the loop-shaped area follow a tangent of either a negatively curved or a positively curved part of a hypothetical ellipse or circle; and
wherein the central area surrounded by the loop-shaped area comprises a plurality of non-spherical magnetic or magnetizable particles, wherein a part of the plurality of non-spherical magnetic or magnetizable particles within the central area are oriented such that their longest axis is substantially parallel to the plane of the OEL, forming the optical effect of a protrusion within the central area of the loop-shaped area.

2. The optical effect layer (OEL) according to claim 1 , wherein the OEL comprises an external area outside the closed loop-shaped area, and the external area surrounding the loop-shaped area comprises a plurality of non-spherical magnetic or magnetizable particles, wherein a part of the plurality of non-spherical magnetic or magnetizable particles within the external area are oriented such that their longest axis is substantially perpendicular to the plane of the OEL or randomly oriented.

3. The optical effect layer (OEL) according to claim 1 , wherein at least a part of an outer peripheral shape of the protrusion is similar to the shape of the loop-shaped area.

4. The optical effect layer (OEL) according to claim 3 , wherein the loop-shaped area has the form of a ring, and the protrusion has the shape of a solid circle or a half-sphere.

5. The optical effect layer (OEL) according to claim 1 , wherein at least a part of the plurality of non-spherical magnetic or magnetizable particles comprise non-spherical optically variable magnetic or magnetizable pigments.

6. The optical effect layer (OEL) according to claim 5 , wherein the non-spherical optically variable magnetic or magnetizable pigments are selected from the group consisting of magnetic thin-film interference pigments, magnetic cholesteric liquid crystal pigments and mixtures thereof.

7. An optical effect coated substrate (OEC) comprising one or more optical effect layers according to claim 1 on a substrate.

8. A security document comprising an optical effect layer recited in claim 1 .

9. The security document according to claim 8 being one of a banknote or an identify document.

10. A method of forming a security document protected against counterfeiting or fraud or with a decorative application, comprising applying the optical effect layer recited in claim 1 onto the security document.

11. A magnetic-field-generating device for forming an optical effect layer, said device being configured for receiving a coating composition on a supporting surface or on a substrate, the coating composition comprising a plurality of non-spherical magnetic or magnetizable particles and a binder material, the device comprising more than one magnet below the supporting surface, the magnets being arranged rotatable around an axis of rotation that is substantially perpendicular to the supporting surface,
the device being configured for orienting at least a part of the plurality of non-spherical magnetic or magnetizable particles in parallel to the plane of the optical effect layer in at least a loop-shaped area thereof, wherein, in a cross-section perpendicular to the OEL and extending from the center of the central area, the longest axis of the oriented particles present in the loop-shaped area follow a tangent of either a negatively curved or a positively curved part of a hypothetical ellipse or circle, and being configured to orient a part of the plurality of non-spherical magnetic or magnetizable particles within the central area such that their longest axis is substantially parallel to the plane of the OEL, forming the optical effect of a protrusion within the central area of the loop-shaped area.

12. The magnetic-field-generating device according to claim 11 , which either
a) comprises a supporting surface for receiving the coating composition, and the supporting surface is formed by
a1) a plate on which the coating composition can be applied directly,
a2) a plate for receiving a substrate on which the coating composition can be applied, or
b) is configured for receiving a substrate on which the optical effect layer is to be provided, said substrate replacing the supporting surface.

13. The magnetic-field-generating device according to claim 11 , said device comprising a supporting surface or being configured to receive a substrate replacing the supporting surface, wherein, upon rotation of the magnets around the axis of rotation, time dependently magnetic field lines that are substantially parallel to the supporting surface are generated in an area defining a loop-shape and within a central area surrounded by the loop-shape and being spaced apart from the loop-shape, the device comprising either
a) one or more pairs of bar dipole magnets below the supporting surface and rotatable around an axis of rotation that is substantially perpendicular to the supporting surface, said magnets having their North-South axis substantially parallel to the supporting surface and their magnetic North-South axis substantially radial with respect to the axis of rotation and
the same magnetic North-South direction
the one or more pairs being each formed by two bar dipole magnets that are located substantially symmetrically about the axis of rotation;
b) one or more pairs of bar dipole magnets below the supporting surface and rotatable around an axis of rotation that is substantially perpendicular to the supporting surface, said magnets having i) their North-South axis substantially perpendicular to the supporting surface, ii) their magnetic North-South axis substantially parallel to the axis of rotation, and iii) opposite magnetic North-South directions, the one or more pairs each consisting of assemblies of two bar dipole magnets being symmetrically disposed about the axis of rotation;
c) three bar dipole magnets below the supporting surface and provided rotatable around an axis of rotation that is substantially perpendicular to the supporting surface, wherein two of the three bar dipole magnets are located on opposite sides and about the axis of rotation, and the third bar dipole magnet is positioned on the axis of rotation, and wherein i) each of the magnets has its North-South axis substantially parallel to the supporting surface, ii) the two magnets spaced apart from the axis of rotation have their North-South axis substantially radial with respect to the axis of rotation, iii) the two bar dipole magnets spaced apart from the axis of rotation have identical North-South directions asymmetric with respect to the axis of rotation, and iv) the third bar dipole magnet on the axis of rotation has a North-South direction opposite to the North-South direction of the two bar dipole magnets spaced apart.

14. The magnetic-field-generating device according to claim 13 , wherein the loop-shaped area provides the optical impression of a loop-shaped area that takes the form of a ring, and the central area surrounded by the loop-shaped area provides the optical impression of a sol

Assignees

• Sicpa Holding Sa

Inventors

• Schmid Mathieu
• Loginov Evgeny
• Despland Claude Alain
• Degott Pierre

Classifications

• B41M3/148

  Transitory images, i.e. images only visible from certain viewing angles · CPC title

• H01F7/0273

  Magnetic circuits with PM for magnetic field generation · CPC title

• B05D3/20 Primary

  by magnetic fields · CPC title

• B05D3/207

  post-treatment by magnetic fields · CPC title

• G07D7/003

  using security elements (using digital security elements G07D7/004) · CPC title