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Final Report Summary - FLEXPAET (Flexible Patterning of Complex Micro Structures using Adaptive Embossing Technology)

Light is one of the most fundamental and integral parts of modern living. It is required in almost every aspect of life ranging from general illumination over simple signalling systems such as traffic lights to complex information transmission for example in monitors, displays and TV-sets. In recent years, light applications have become increasingly more sophisticated. Luminaires have developed from simple illuminators to lighting elements, integrated into complex building and interior concepts, designed to create high quality, functional environments. Large area, high resolution displays are becoming more and more common in everyday life and are used to provide information, advertising and entertainment. Monitors and TV sets at the same time are becoming smaller, while offering high quality images and more and more complex functionalities.
Structured and planar light guides posse ideal properties as optics for the lighting engineering. Thereby complex and 3-dimensional microstructures make a visual functionality possible. The production of large-area components with micro structured surfaces confronted industrial production processes with so far irresolvable problems. Flexible micro structuring with step and repeat hot embossing processes provides the opportunity to eliminate the production-related deficits of previous processes. Within the context of the research project »FlexPAET« an adaptive hot embossing process and its integration in a process chain of a cost-effective production of planar lighting optics was developed.
The developed machine demonstrator imprints systematically the structures of complex micro tools into a thermoplastic substrate. In contrast to the conventional process of hot embossing, singular structural elements are put together piece by piece on one surface. In surfaces up to 1x2 m² the machine can imprint microstructures with a positioning accuracy of 2 μm. Concerning flexibility and speed unknown opportunities with regard to the production of visual functionalised surfaces result.
The optical function of the embossed component is measured directly in the machine system by means of integrated metrology. Thus errors in the optical design can be detected directly on the machine. An algorithm compares the optical function of the embossed component with the required values. In this manner, the system identifies those positions on the surface where the structure has to be improved. The optimisation process will be proceeded until the measured optical properties correspond to the required specifications.
The process is part of a replication process chain that fits to mass-production. Similar to the approach of CD and DVD production, form tools were produced out of the embossed component by means of galvanic electroforming processes, enabling the cost efficient production of high quality optics.
FlexPAET covered the entire production process, starting with the optical design, the production of master substrates, the measurement of the optical behaviour and iterative remachining of the masters, material development, and mass replication technologies. The developed technology enables economic production of advanced light guide products for LED lighting.

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