Improvement of UV-moulding accuracy by heat and solvent assisted process

A micro-optics replication process with UV-curable liquid pre-polymers is considered. Filling of the master structure is improved by controlling the viscosity of the pre-polymer by heat during the process. A novel process step, solvent-assisted filling, is introduced to avoid the harmful effect of the residual trapped air; a pyramidal retro-reflector structure with the face width of 400 μm is used as an example. Complete filling can be achieved without vacuum assisted replication or without application of compression force in the mould. Material studies showed no signs of chemical changes, solvent inclusion in the replicated structure, or a change of the optical properties of the material during the process. The replication fidelity is compared with conventional UV-moulding and commercial UV-NIL replication. The new heat and solvent assisted replication technique allows the use of high-viscosity pre-polymers with suitable material properties if the process temperature window is optimized.