Security elements, and methods and apparatus for their manufacture

A security element comprising a layer disposed on a substrate, the layer comprising a composition having magnetic or magnetisable particles therein, each particle having at least one substantially planar surface,

• wherein the magnetic or magnetisable particles vary in orientation across the layer such that:
• at a first part of the layer, the particles are orientated with their planar surfaces substantially parallel to the normal to the layer, the angle between the planar surfaces of the particles and the normal gradually increasing with increasing radial distance from the first part to a maximum of approximately 90 degrees at a first radial position of the layer before decreasing gradually again until a second, farther, radial position of the layer, the normals to the planar surfaces of the particles disposed between the first part and the second radial position intersecting one another at points on a first side of the layer, and
• from the second radial position, the angle between the planar surfaces of the particles and the normal of the layer gradually increases with increasing radial distance, the normals to the planar surfaces of the particles intersecting one another at points on a second side of the layer, opposite to the first side,
• such that the security element displays a bright edge corresponding to the first radial position, between a first dark area which includes the first part of the layer, and a second dark area, at least when the security element is viewed along a direction substantially normal to the plane of the substrate.