Optical security element

A method for printing an optical security element on a substrate, comprising:

• providing, on the substrate, a binder that includes a plurality of magnetizable bifunctional pigment flakes, wherein a magnetizable bifunctional pigment flake in the plurality of magnetizable bifunctional pigment flakes comprises a first surface having a diffraction grating relief with a first modulation and a second surface with a second modulation that is smaller than the first modulation;
• applying a magnetic field to the binder using one or more magnets, wherein the magnetic field orients the plurality of magnetizable bifunctional pigment flakes according to the magnetic field, wherein the plurality of magnetizable bifunctional pigment flakes are oriented such that, in a presence of incident light:
• a set of colors are exhibited in a first region of the optical security element by a first subset of the plurality of magnetizable bifunctional pigment flakes, and
• a different color is exhibited in a second region of the optical security element by a second subset of the plurality of magnetizable bifunctional pigment flakes;
• and setting or hardening the binder.

A printed optical security element, comprising:

• a first region comprising a first subset of a plurality of bifunctional pigment flakes disposed in a binder,
• wherein the first subset of the plurality of bifunctional pigment flakes are arranged such that, in a presence of incident light, a set of colors are exhibited in the first region of the printed optical security element, and
• a second region comprising a second subset of the plurality of bifunctional pigment flakes disposed in the binder,
• wherein the second subset of the plurality of bifunctional pigment flakes are arranged such that, in the presence of the incident light, another color is exhibited in the second region of the printed optical security element,
• wherein the first region is distinct from the second region such that the set of colors and the other color are non-blended.