Coextrusion of periodically modulated structures

A method for manufacturing a foil having a variable strip geometry for employment in a data carrier, the method comprising:

• melting different materials to supply at least one first surface and at least one second surface for a security element;
• extruding at least one first surface and at least one second surface;
• varying at least one of the surfaces with respect to its geometry by:
• transverse movement of at least one roller of an extruder;
• movement of a position-variable distributor rail of the extruder;
• and
• an adaptation of a melt flow in the extruder, wherein the adaptation of the melt flow is a structural adaptation configured to vary a path of the melt flow in the extruder;
• introducing color pixels into at least one of the surfaces by means of a matrix block having punctiform and/or elliptical passages;
• changing material properties of at least one of the surfaces in a flow direction along a length of said at least one of the surfaces;
• planarly forming the surfaces of the foil in a sequence that alternates orthogonally to an extrusion direction, the extrusion direction being defined as a direction in which molten material of the surfaces is guided through and out of the extruder;
• creating a security feature based on the sequence of the at least one first and second surfaces;
• wherein at least one of the surfaces is formed in a meandering manner, strip-shaped manner and/or with varying width;
• wherein the variable strip geometry is defined as adapting individual strips of the at least one first surface and the at least one second surface with respect to width and in extension along a length of the individual strips;
• wherein the adapting of individual strips results in the at least one first surface being narrower than the at least one second surface;
• wherein the step of changing material properties of at least one of the surfaces includes splitting at least one of the surfaces into subdivided, partial surfaces having alternating materials with respect to the extrusion direction.