Patent ID: 9659696
Date: 2017-05-23
CPC Classifications: B05D,B42D,H01F

Claim:
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 b) a pair of bar dipole magnets (M c) a pair of bar dipole magnets (M 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.