Appartuses and processes for producing optical effect layers comprising oriented non-spherical magnetic or magnetizable pigment particles

Patent metadata

Field	Value
Publication number	US-10906066-B2
Application number	US-201615769571-A
Country	US
Kind code	B2
Filing date	Sep 7, 2016
Priority date	Nov 10, 2015
Publication date	Feb 2, 2021
Grant date	Feb 2, 2021

Abstract

The present invention relates to the field of magnetic assemblies and processes for producing optical effect layers (OEL) comprising magnetically oriented non-spherical magnetic or magnetizable pigment particles on a substrate. In particular, the present invention relates magnetic assemblies and processes for producing said OELs as anti-counterfeit means on security documents or security articles or for decorative purposes.

First claim

The invention claimed is:

1. A process for producing an optical effect layer on a substrate, said process comprising the steps of:
i) applying on a substrate surface a radiation curable coating composition comprising non-spherical magnetic or magnetizable pigment particles, said radiation curable coating composition being in a first state,
ii) exposing the radiation curable coating composition to a magnetic field of an apparatus comprising:
a) a magnetic assembly comprising a non-magnetic supporting matrix and:
a1) a loop-shaped magnetic-field generating device being either a single loop-shaped dipole magnet having a magnetic axis substantially perpendicular to the substrate surface or a combination of two or more dipole magnets disposed in a loop-shaped arrangement, each of the two or more dipole magnets having a magnetic axis substantially perpendicular to the substrate surface and having a same magnetic field direction, and
a2) a single dipole magnet having a magnetic axis substantially perpendicular to the substrate surface or two or more dipole magnets having a magnetic axis substantially perpendicular to the substrate surface and having a same magnetic field direction and/or one or more pole pieces,

b) a magnetic-field generating device being either a single bar dipole magnet having a magnetic axis substantially parallel to the substrate surface or a combination of two or more bar dipole magnets, each of the two or more bar dipole magnets having a magnetic axis substantially parallel to the substrate surface and having a same magnetic field direction,

so as to orient at least a part of the non-spherical magnetic or magnetizable pigment particles, and
iii) at least partially curing the radiation curable coating composition of step ii) to a second state so as to fix the non-spherical magnetic or magnetizable pigment particles in their adopted positions and orientations,
wherein the optical effect layer provides an optical impression of one or more loop-shaped bodies having a size that varies upon tilting the optical effect layer,
wherein the magnetic assembly and the magnetic-field generating device are arranged one on top of the other and are in direct contact,
wherein the loop-shaped magnetic-field generating device and the single dipole magnet or the two or more dipole magnets of the magnetic assembly are disposed within the non-magnetic supporting matrix.

2. The process according to claim 1 , wherein the magnetic assembly comprises the supporting matrix and:
a1) the loop-shaped magnetic-field generating device, and
a2) the single dipole magnet or the two or more dipole magnets and the one or more pole pieces.

3. The process according to claim 1 , 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 pigment particles.

4. The process according to claim 3 , wherein the 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.

5. The process according to claim 1 , wherein step iii) is carried out partially simultaneously with the step ii).

6. The process according to claim 1 , wherein the non-spherical magnetic or magnetizable particles are platelet-shaped pigment particles, and wherein said process further comprises a step of exposing the radiation curable coating composition to a dynamic magnetic field of a first magnetic-field-generating device so as to bi-axially orient at least a part of the platelet-shaped magnetic or magnetizable pigment particles, said step being carried out after step i) and before step ii).

7. An optical effect layer produced by the process recited in claim 1 .

8. A security document or a decorative element or object comprising one or more optical effect layers recited in claim 7 .

9. The process according to claim 1 , wherein the radiation curable coating composition on the substrate is exposed to the magnetic field of the apparatus above one side of the magnetic assembly and the magnetic-field generating device is arranged on an opposite side of the magnetic assembly.

10. The process according to claim 1 , wherein the optical effect layer provides an optical impression of one or more loop-shaped bodies having a size that varies upon tilting the optical effect layer and the one or more loop-shaped bodies appear to continually vary in size as an angle at which the optical effect layer is tilted changes.

11. The process according to claim 1 , wherein step i) is carried out by a printing process.

12. The process according to claim 11 , wherein the printing process is selected from the group consisting of screen printing, rotogravure printing and flexography printing.

13. The process according to claim 1 , wherein the optical effect layer provides an optical impression of one or more loop-shaped bodies having a size that continually increases or continually decreases as the optical effect layer is tilted from a negative viewing angle to a positive viewing angle.

Assignees

• Sicpa Holding Sa

Inventors

• Loginov Evgeny
• Schmid Mathieu
• Despland Claude-Alain

Classifications

• H01F41/16

  the magnetic material being applied in the form of particles, e.g. by serigraphy {, to form thick magnetic films or precursors therefor} (H01F41/18 {-H01F41/24} take precedence) · CPC title

• B42D25/30

  Identification or security features, e.g. for preventing forgery · CPC title

• H01F7/0284

  using a trimmable or adjustable magnetic circuit, e.g. for a symmetric dipole or quadrupole magnetic field · CPC title

• B42D25/369

  Magnetised or magnetisable materials · CPC title

• B05D3/207 Primary

  post-treatment by magnetic fields · CPC title