The disclosure relates to the field of graphical elements and is directed to an optical effect layer (OEL), a device and a method for producing same. The disclosure provides an optical effect that is easy to detect as such and exhibits a viewing-angle dependent apparent motion of image features over an extended length if the viewing angle with respect to the OEL changes. An OEL includes a binder material being at least partially transparent and a plurality of particles dispersed within the layer. Each particle has a non-isotropic reflectivity and may be magnetic or magnetizable. The orientation of the particles forms an orientation pattern extending over a length within an extended surface of the OEL, such that the local average of an angle between (i) a straight line along an observed longest dimension within the corresponding cross-section shape, and (ii) said first direction x varies according to a function () of a position (P) along said first direction.

Disclosure relates to the field of graphical elements and is directed to a device for producing an optical effect layer (OEL). Disclosure provides an optical effect that is easy to detect as such and exhibits a viewing-angle dependent apparent motion of image features over an extended length if the viewing angle with respect to the OEL changes. OEL includes a binder material being at least partially transparent and a plurality of particles dispersed within the layer. Each particle has a non-isotropic reflectivity and may be magnetic or magnetizable. Orientation of the particles forms an orientation pattern extending over a length within an extended surface of the OEL, such that the local average of an angle between (i) a straight line along an observed longest dimension within the corresponding cross-section shape, and (ii) said first direction x varies according to a function () of a position (P) along said first direction.

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.