Method of, and apparatus for, simultaneous dual-sided imprinting

A method for simultaneous dual-sided direct nanoimprint lithography of surface relief structures on a substrate, the method utilising a nanoimprint lithography arrangement comprising first and second rotatable cylinders, each rotatable cylinder being arranged to carry at least one mould having a surface relief structure, each rotatable cylinder comprising a resilient layer located between a cylindrical outer surface of the respective rotatable cylinder and the respective mould, and the rotatable cylinders being movable with respect to one another and arranged to form an imprinting nip therebetween, the imprinting nip having an imprinting contact area, wherein the method comprises the steps of:

• a) providing to the imprinting nip a substrate comprising first and second sides each having a curable medium thereon;
• b) directly nanoimprinting surface relief structures into the curable medium on both the first and second sides of the substrate by passing the substrate through the imprinting nip and engaging, in the imprinting contact area, a first mould on the first rotatable cylinder with the curable medium on the first side of the substrate and a second mould on the second rotatable cylinder with the curable medium on the second side of the substrate;
• and
• c) illuminating, in the imprinting nip, at least a part of the curable media on the first and second sides of the substrate with curing radiation to at least partially cure the curable media on the substrate as the substrate passes through the imprinting nip;
• wherein step c) further comprises illuminating the substrate with at least one illumination arrangement having an illumination region located within the imprinting contact area;
• and
• wherein step c) further comprises varying the position of the illumination region within the imprinting contact area by rotating the illumination arrangement or translating the illumination arrangement in a direction parallel to the direction of movement of the substrate passing through the imprinting nip.