Permanent magnet assemblies for generating concave field lines and process for creating optical effect coating therewith (inverse rolling bar)

Patent metadata

Field	Value
Publication number	US-9659696-B2
Application number	US-201414898007-A
Country	US
Kind code	B2
Filing date	Jun 13, 2014
Priority date	Jun 14, 2013
Publication date	May 23, 2017
Grant date	May 23, 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 magnetic-field-generating devices which produce positively curved magnetic field lines in a concave fashion. The invention also relates to the use of these magnetic-field-generating devices for producing optical effect layers OEL which exhibit the optical impression of a positive rolling bar effect and to processes using these magnetic-field-generating devices, e.g. in the field of document security.

First claim

The invention claimed is:

1. A process for producing an optical effect layer (OEL) comprising:
a) applying on a supporting surface a coating composition comprising a binder and a plurality of non-spherical magnetic or magnetizable pigment particles, said coating composition being in a first state,
b) exposing the coating composition in a first state to the magnetic field of a magnetic-field-generating device receiving the supporting surface, thereby orienting at least a part of the non-spherical magnetic or magnetizable pigment particles so as to form a positive rolling bar effect, the magnetic-field generating device is located on the side of the supporting surface opposite to the side carrying the coating composition, and
c) hardening the coating composition to a second state so as to fix the non-spherical magnetic or magnetizable pigment particles in their adopted positions and orientations,
wherein said magnetic-field-generating device is configured for receiving the supporting surface carrying the coating composition, and is configured for forming concave magnetic field lines for orienting at least the part of the plurality of non-spherical magnetic or magnetizable pigment particles in an orientation forming the positive rolling bar effect, and
wherein said magnetic-field-generating device is:
a) a bar dipole magnet (M 1 ) and a pair of bar dipole magnets (M 2 ) and (M 3 ), said bar dipole magnets (M 1 ), (M 2 ) and (M 3 ) having their North-South axis substantially parallel to the supporting surface and the same magnetic North-South direction,
a1) said bar dipole magnet (M 1 ) is disposed below the supporting surface and said pair of bar dipole magnets (M 2 ) and (M 3 ) are disposed below the bar dipole magnet (M 1 ) apart from each other; or
a2) said pair of bar dipole magnets (M 2 ) and (M 3 ) are disposed below the supporting surface and apart from each other, and said bar dipole magnet (M 1 ) is disposed below said pair of bar dipole magnets (M 2 ) and (M 3 ); or

b) a pair of bar dipole magnets (M 4 ) and (M 5 ) and a pole piece (Y), said pair of bar dipole magnets (M 4 ) and (M 5 ) having their North-South axis substantially parallel to the supporting surface and the same magnetic North-South direction, said pole piece (Y) being disposed between said bar dipole magnet (M 4 ) and said bar dipole magnet (M 5 ); or
c) a pair of bar dipole magnets (M 4 ) and (M 5 ), a pole piece (Y) and a magnetic plate (M 6 ), said pair of bar dipole magnets (M 4 ) and (M 5 ) having their North-South axis substantially parallel to the supporting surface and the same magnetic North-South direction, said magnetic plate (M 6 ) having its North-South axis substantially perpendicular to the supporting surface, said pole piece (Y) being disposed between said bar dipole magnet (M 4 ) and said bar dipole magnet (M 5 ); or
d) wherein said magnetic field generating device comprises a pair of spaced apart bar dipole magnets and a third element, preferably a third dipole magnet or a pole piece, wherein the dipole magnets have north to south axes that are aligned with each other, that are substantially parallel to the supporting surface and that have a same magnetic North-South direction, wherein the dipole magnets are spaced apart along the north south axes so as to provide a gap region between the dipole magnets in which magnetic field lines are such that the magnetic or magnetizable pigment particles are oriented in the gap region to form the positive rolling bar effect and wherein the third element is arranged with the pair of spaced dipole bar magnets to disturb the magnetic field in the gap region between the spaced apart bar dipole magnets.

2. The process of claim 1 , wherein the supporting surface is a substrate on which the coating composition (C) is applied, or a combination of a non-magnetic plate and a substrate.

3. The process of claim 1 , wherein said magnetic-field-generating device is the pair of bar dipole magnets (M 4 ) and (M 5 ), the pole piece (Y) and the magnetic plate (M 6 ), wherein the magnetic plate (M 6 ) surface facing the supporting surface comprises engravings.

4. The process of claim 1 , wherein said magnetic field generating device comprises the pair of spaced apart bar dipole magnets and the third element, wherein the third element is the third dipole magnet, and the third dipole magnet has a north south axis aligned with the north south axes of the pair of spaced apart bar dipole magnets and has a same magnetic North-South direction; and the pair of spaced apart bar dipole magnets each have a pole facing the gap region, wherein the facing poles are spaced apart to form the gap region and are positioned adjacent to the opposed polar sides of the third dipole magnet.

5. The process of claim 1 , wherein the pair of bar dipole magnets are disposed at a periphery or outside of a periphery of the coating composition and are configured to produce magnetic field lines in a gap region between the bar dipole magnets to create the positive rolling bar effect in the coating composition in the gap region.

6. The process of claim 1 , wherein at least one of the pair of bar dipole magnets has a length along the north to south axis that is smaller than a space between the pair of bar dipole magnets along the north to south axis.

7. The process of claim 1 , comprising applying the optical effect layer to a security document.

8. The process of claim 7 , wherein the security document is selected from the group consisting of banknotes, identity documents, right-conferring documents, driving licenses, credit cards, access cards, transportation titles, bank checks and secured product labels.

Assignees

• Sicpa Holding Sa

Inventors

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

Classifications

• B42D15/00

  Printed matter of special format or style not otherwise provided for · CPC title

• B05D3/207

  post-treatment by magnetic fields · CPC title

• B42D25/41

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

• B42D25/369

  Magnetised or magnetisable materials · CPC title

• B05D3/20

  by magnetic fields · CPC title