The disclosure 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 disclosure provides processes for producing optical effect layers (OELs) on a substrate and OELs obtained thereof, said process including two magnetic orientation steps: a step of exposing a coating composition having platelet-shaped magnetic or magnetisable pigment particles 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 magnetisable pigment particles, and a step of exposing the coating composition to a static magnetic field of a second magnetic-field-generating device, thereby mono-axially re-orienting at least a part of the platelet-shaped magnetic or magnetisable pigment particles.