Magnetic assemblies, apparatuses and processes for producing optical effect layers comprising oriented non-spherical magnetic or magnetizable pigment particles

Patent metadata

Field	Value
Publication number	US-11577272-B2
Application number	US-201917053721-A
Country	US
Kind code	B2
Filing date	May 7, 2019
Priority date	May 8, 2018
Publication date	Feb 14, 2023
Grant date	Feb 14, 2023

Abstract

The present invention relates to the field of magnetic assemblies, magnetic apparatuses and processes for producing optical effect layers (OEL) comprising magnetically oriented non-spherical magnetic or magnetizable pigment particles on a substrate and providing an impression of a crescent moon-shaped element moving or rotating upon tilting the optical effect layer (OEL). In particular, the present invention relates to magnetic assemblies, magnetic apparatuses 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, said first state being a liquid state;
ii) exposing the radiation curable coating composition to a magnetic field of a magnetic assembly comprising:
a) a first magnetic-field generating device having a North-South magnetic axis substantially perpendicular to the substrate surface and having length L 1 ;
b) a second magnetic-field generating device having a North-South magnetic axis substantially perpendicular to the substrate surface and having a length L 3 ,
c) a flat pole piece lacking any protrusions or projections extending outside a surface of said pole piece and having a length L 5 ,
wherein the first magnetic-field generating device and the second magnetic-field generating device have a same magnetic field direction,
wherein the first magnetic-field generating device faces the substrate and is disposed on top of the pole piece,
wherein the second magnetic-field generating device faces an environment and is disposed below the flat pole piece,
wherein the length L 1 of the first magnetic-field generating device is smaller than the length L 3 of the second magnetic-field generating device,
wherein the length L 1 of the first magnetic-field generating device is smaller than the length L 5 of the flat pole piece, and
wherein the length L 3 of the second magnetic-field generating device is smaller than the length L 5 of the pole piece,

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 adopted positions and orientations,
wherein the optical effect layer provides an optical impression of a moon crescent moving and rotating upon tilting the substrate comprising the optical effect layer.

2. The process according to claim 1 , wherein the magnetic assembly further comprises a non-magnetic plate.

3. The process according to claim 2 , wherein the non-magnetic plate is made of polyoxymethylene.

4. The process according to claim 1 , wherein the magnetic assembly further comprises a second flat pole piece having a length L 9 , wherein said second pole piece is disposed below the second magnetic-field generating device thus facing the environment.

5. The process according to claim 1 , wherein the magnetic assembly further comprises a magnetized plate comprising one or more engravings and/or cut-outs representing one or more indicia,
and
wherein magnetized plate is disposed on top of the first magnetic-field generating device thus facing the substrate.

6. The process according to claim 5 , wherein the magnetized plate is made of a composite material comprising a polymer and a permanent magnetic powder material.

7. The process according to claim 1 , wherein the flat pole piece is made of iron.

8. The process according to claim 1 , wherein the first magnetic-field generating device and the second first magnetic-field generating device are disc-shaped magnetic-field generating devices and length L 1 and L 3 correspond to a diameter of the first magnetic-field generating device and the second first magnetic-field generating device, respectively, or the first magnetic-field generating device and the second first magnetic-field generating device are square-shaped magnetic-field generating devices and length L 1 and L 3 correspond to a width of the first magnetic-field generating device and the second first magnetic-field generating device, respectively.

9. The process according to claim 1 , wherein the non-spherical magnetic or magnetizable pigment particles are selected from the group consisting of magnetic thin-film interference pigments, magnetic cholesteric liquid crystal pigments and mixtures thereof.

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

11. 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).

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

13. A security document or a decorative element or object comprising one or more optical effect layers recited in claim 12 .

14. A magnetic assembly for producing an optical effect layer on a substrate, said optical effect layer providing an impression of a crescent moon-shaped element moving or rotating upon tilting the optical effect layer and comprising oriented non-spherical magnetic or magnetizable pigment particles in a cured radiation curable coating composition, wherein said magnetic assembly comprises:
a) a first magnetic-field generating device having a North-South magnetic axis substantially perpendicular to the substrate surface and having a length L 1 ;
b) a second magnetic-field generating device having a North-South magnetic axis substantially perpendicular to the substrate surface and having a length L 3 ,
c) a flat pole piece lacking any protrusions or projections extending outside a surface of said pole piece and having a length L 5 ,
wherein the first magnetic-field generating device and the second magnetic-field generating device have a same magnetic field direction,
wherein the first magnetic-field generating device faces the substrate and is disposed on top of the pole piece,
wherein the second magnetic-field generating device faces an environment and is disposed below the pole piece,
wherein the length 1 of the first magnetic-field generating device is smaller than the length L 3 of the second magnetic-field generating device,
wherein the length L 1 of the first magnetic-field generating device is smaller than the length L 5 of the pole piece, and
wherein the length L 3 of the second magnetic-field generating device is smaller than the length L 5 of the pole piece.

15. The magnetic assembly according to claim 14 further comprising a non-magnetic plate and/or
further comprising a second flat pole piece having a length L 9 , wherein said second pole piece is disposed below the second magnetic-field generating device thus facing the environment and wherein the length L 1 of the first magnetic-field generating device is smaller than the length L 9 of said second pole piece and the length L 3 of the second magnetic-field generating device is smaller than the length L 9 of said second pole piece, and/or
further comprising a magnetized plate comprising one or more engravings and/or cut-outs representing one or more indicia, and wherein magnetized plate is disposed on top of the first magnetic-field generating device thus facing the substrate.

16. The magnetic assembly according to claim 15 , wherein said magnetized plate is made of a composite material comprising a polymer and a permanent magnetic powder material.

17. The magnetic assembly according to claim 14 , wherein the magnetic assembly is dispo

Assignees

• Sicpa Holding Sa

Inventors

• Amerasinghe Cédric
• Schmid Mathieu
• Despland Claude-Alain

Classifications

• H01F7/0273

  Magnetic circuits with PM for magnetic field generation · CPC title

• B42D25/369

  Magnetised or magnetisable materials · CPC title

• B05D5/065

  having colour interferences or colour shifts or opalescent looking, flip-flop, two tones · CPC title

• C09D11/037

  characterised by the pigment · CPC title

• B05D3/207 Primary

  post-treatment by magnetic fields · CPC title