Assemblies and processes for producing optical effect layers comprising oriented magnetic or magnetizable pigment particles

Patent metadata

Field	Value
Publication number	US-12020864-B2
Application number	US-201917264141-A
Country	US
Kind code	B2
Filing date	Jul 26, 2019
Priority date	Jul 30, 2018
Publication date	Jun 25, 2024
Grant date	Jun 25, 2024

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 present invention provides processes for optical effect layers (OEL) exhibiting one or more indicia using a magnetic assembly comprising i) a soft magnetic plate (x 31 ) comprising a) one or more voids (V) and b) one or more dipole magnets (x 32 - a ), wherein the one or more dipole magnets (x 32 - a ) are disposed within the one or more voids (V) and/or are facing said one or more voids (V), and/or one or more pairs of two dipole magnets (x 32 - b ), wherein the dipole magnets (x 32 - b ) of the one or more pairs are disposed below the soft magnetic plate (x 31 ) and are spaced apart from the one or more voids (V).

First claim

The invention claimed is:

1. A magnetic assembly mounted on a transferring device and comprising
i) a soft magnetic plate made of a composite comprising from about 25 wt-% to about 95 wt-% of spherical soft magnetic particles dispersed in a non-magnetic material, the weight percents being based on the total weight of the soft magnetic plate, wherein the soft magnetic plate comprises one or more voids, wherein each of the one or more voids either completely extends through the soft magnetic plate or partially extends through the soft magnetic plate, and
ii) one or more dipole magnets, wherein the one or more dipole magnets are permanent dipole magnets, and wherein the one or more dipole magnets are disposed within the one or more voids and/or are outside of the one or more voids and facing the one or more voids,
wherein if any of the one or more dipole magnets are disposed within any of the one or more voids, either (a) more than one dipole magnet is disposed within a single void of the one or more voids and some of the dipole magnets disposed within the single void have opposite magnetic directions, or b) one or more of the dipole magnets facing at least one of the one or more voids are also present, and
wherein if any of the one or more dipole magnets are outside of the one or more voids and facing the one or more voids, the dipole magnets outside of and facing the one or more voids are below the soft magnetic plate and the dipole magnets outside of and facing the one or more voids are directly under the one of the one or more voids.

2. The magnetic assembly according to claim 1 , wherein said magnetic assembly is disposed in a holder mounted on a transferring device being a rotating magnetic cylinder and wherein the soft magnetic plate has a curved surface fitting with the curved surface of the rotating magnetic cylinder.

3. The magnetic assembly according to claim 1 , wherein each of said one or more dipole magnets has its magnetic axis substantially perpendicular to the soft magnetic plate surface and all of said one or more dipole magnets facing said one or more voids have a same magnetic direction.

4. The magnetic assembly according to claim 1 , wherein a polymeric matrix of the soft magnetic plate comprises or consists of one or more thermoplastic materials selected from the group consisting of polyamides, co-polyamides, polyphtalimides, polyolefins, polyesters, polytetrafluoroethylenes, polyacrylates, polymethacrylates, polyimides, polyetherimides, polyetheretherketones, polyaryletherketones, polyphenylene sulfides, liquid crystal polymers, polycarbonates and mixtures thereof or one or more thermosetting materials selected from the group consisting of epoxy resins, phenolic resins, polyimide resins, silicon resins and mixtures thereof, and wherein the spherical soft magnetic particles are selected from the group consisting of carbonyl iron, carbonyl nickel, cobalt and combinations thereof and have a d50 between about 0.5 μm and about 100 μm.

5. The magnetic assembly according to claim 1 , wherein the soft magnetic plate has a thickness of at least about 0.5 mm.

6. The magnetic assembly according to claim 1 , wherein the soft magnetic plate has a thickness of at least about 1 mm.

7. The magnetic assembly according to claim 1 , wherein the soft magnetic plate has a thickness between about 1 mm and about 5 mm.

8. The magnetic assembly according to claim 1 , wherein the one or more dipole magnets are disposed within the one or more voids.

9. A printing apparatus comprising a transferring device and at least one of the magnetic assemblies recited in claim 1 .

10. The printing apparatus according to claim 9 , wherein the transferring device is a rotating magnetic cylinder comprising at least one of the magnetic assemblies mounted thereon.

11. A process for producing an optical effect layer exhibiting one or more indicia on a substrate, said process comprising the steps of:
a) applying onto a substrate surface a coating composition comprising i) platelet-shaped magnetic or magnetizable pigment particles and ii) a binder material so as to form a coating layer on said substrate, said coating composition being in a first liquid state;
b) exposing the coating layer to a magnetic field of the magnetic assembly recited in claim 1 ; and
c) hardening the coating composition to a second state so as to fix the platelet-shaped magnetic or magnetizable pigment particles in their adopted positions and orientations.

12. The process according to claim 11 , wherein the platelet-shaped magnetic or magnetizable pigment particles are platelet-shaped optically variable magnetic or magnetizable pigment particles selected from the group consisting of platelet-shaped magnetic thin-film interference pigment particles, platelet-shaped magnetic cholesteric liquid crystal pigment particles, platelet-shaped interference coated pigment particles comprising a magnetic material and mixtures of two or more thereof.

13. The process according to claim 11 further comprising a step of exposing the coating layer to a dynamic magnetic field of a device so as to bi-axially orient at least a part of the platelet-shaped magnetic or magnetizable pigment particles, said step occurring prior to or simultaneously with step b) and before step c).

14. The magnetic assembly according to claim 1 , wherein the magnetic assembly further comprises one or more pairs of two dipole magnets disposed below the soft magnetic plate, wherein each pair of the one or more pairs of two dipole magnets are spaced apart from one another by the width of the one or more voids.

15. The magnetic assembly according to claim 14 , wherein each of the dipole magnets of the one or more pairs has its magnetic axis substantially perpendicular to the soft magnetic plate surface and each pair of said one or more pairs has two dipole magnets having a same magnetic direction or having an opposite magnetic direction.

16. The magnetic assembly according to claim 14 , wherein one of the one or more dipole magnets has a magnetic axis substantially parallel to the soft magnetic plate surface, wherein said dipole magnet is disposed within the one or more voids or is facing said one or more voids and one or more pairs of two dipole magnets, wherein the one or more pairs of dipole magnets are disposed below the soft magnetic plate and are spaced apart from the one or more voids.

17. The magnetic assembly according to claim 14 , wherein the lateral surface of two dipole magnets of said one or more pairs of two dipole magnets is flush with the external surface of the one or more voids.

18. The magnetic assembly according to claim 17 , wherein the one or more pairs of two dipole magnets are attached to a side of the soft magnetic plate opposite from a side that is configured for placement of a substrate.

Assignees

• Sicpa Holding Sa

Inventors

• Nikseresht Ghanepour Neda
• Schmid Mathieu
• Despland Claude-Alain
• Mueller Edgar

Classifications

• B41M7/0072

  using mechanical wave energy, e.g. ultrasonics; using magnetic or electric fields, e.g. electric discharge, plasma · CPC title

• B41M3/14

  Security printing {(securities B42D25/29)} · CPC title

• B42D25/41

  using electromagnetic radiation (B42D25/435 takes precedence) · CPC title

• B42D25/378

  Special inks · CPC title

• B42D25/369 Primary

  Magnetised or magnetisable materials · CPC title