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

A process for producing an optical effect layer (OEL) on a substrate, said process comprising the steps of:

• a) 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,
• b) exposing the radiation curable coating composition to a resulting magnetic field of a magnetic assembly comprising
• i) a loop-shaped magnetic-field generating device being either a single loop-shaped dipole magnet having a North-South magnetic axis substantially perpendicular to the substrate surface or a combination of two or more dipole magnets disposed in a loop-shaped arrangement and having a resulting North-South magnetic axis substantially perpendicular to the substrate surface, and
• ii) a magnetic-field generating device being either a single bar dipole magnet having a North-South magnetic axis substantially parallel to the substrate surface or a combination of two or more bar dipole magnets having a resulting North-South magnetic axis substantially parallel to the substrate surface,
• so as to orient at least a part of the non-spherical magnetic or magnetizable pigment particles, and
• c) at least partially curing the radiation curable coating composition of step b) to a second state so as to fix the non-spherical magnetic or magnetizable pigment particles in their adopted positions and orientations,
• wherein the loop-shaped magnetic-field generating device and the magnetic-field generating device are in direct contact,
• wherein the resulting magnetic field results from an interaction between the loop-shaped magnetic-field generating device and the magnetic-field generating device, and
• wherein the optical effect layer provides an optical impression of a loop-shaped body having a size that varies upon tilting the optical effect layer.