Roll-to-roll method and system for micro-replication of a pattern of large relief three-dimensional microstructures

Abstract

A method and system referred to as PALM (Patterning by Adhesive of Large Relief Three-Dimensional Microstructures) with large reliefs exceeding 1 μm and being as large as 100 μm. The microstructures can be either deterministic (such as microprisms), or random (such as diffusers), the first obtained by copying an original supermaster, and latter obtained by copying a laser speckle pattern. The master process entails copying a supermaster into the form of the microstructure constituting a pattern on the patterning cylinder (called a drum), to be then continuously multiplied in the PALM system, in a continuous roll-to-roll web process. The latter method, together with the related system, is the subject of this invention. The rolls continuously repeat the master pattern, copying by adhesive with large viscosity on acrylic (hybrid) as well as by a monolithic process. The monolithic process can be accomplished using temperature and pressure, or by UV-cured polymerization. Therefore, the invention comprises three alternative processes: one, hybrid (adhesive on acrylic), and two monolithic ones. In the PALM (hybrid) process, an epoxy is wet-coated on film substrates such as polycarbonate (PC), polyester (PET), (PE), or other flexible material. The adhesive, in liquid form, is applied to the substrate by a self-metered coating sub-process. In the present invention, the adhesive is used for forming the microstructure pattern. The microstructure pattern is replicated from a master roll or image drum onto a coating roll.