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Injection moulding of optical functional micro structures using laser structured, PVD-coated mould inserts

: Hopmann, C.; Weber, M.; Schöngart, M.; Schäfer, C.; Bobzin, K.; Bagcivan, N.; Brögelmann, T.; Theiß, S.; Münstermann, T.; Steger, M.


Polymer Processing Society -PPS-:
PPS 2014, 30th International Conference of the Polymer Processing Society - Conference Papers. Proceedings : Cleveland, Ohio, USA, 6 - 12 June 2014
Woodbury, N.Y.: AIP, 2015 (AIP Conference Proceedings 1664)
ISBN: 978-0-7354-1309-2
Art. 110003, 6 pp.
Polymer Processing Society (PPS International Conference) <30, 2014, Cleveland/Ohio>
Conference Paper
Fraunhofer ILT ()

Micro structured optical plastics components are intensively used i.e. in consumer electronics, for optical sensors in metrology, innovative LED-lighting or laser technology. Injection moulding has proven to be successful for the large-scale production of those parts. However, the production of those parts still causes difficulties due to challenges in the moulding and demoulding of plastics parts created with laser structured mould inserts. A complete moulding of the structures often leads to increased demoulding forces, which then cause a breaking of the structures and a clogging of the mould. An innovative approach is to combine PVD-coated (physical vapour deposition), laser structured inserts and a variothermal moulding process to create functional mic8iuro structures in a one-step process. Therefore, a PVD-coating is applied after the laser structuring process in order to improve the wear resistance and the anti-adhesive properties against the plastics melt. In a series of moulding trials with polycarbonate (PC) and polymethylmethacrylate (PMMA) using different coated moulds, the mould temperature during injection was varied in the range of the glass transition and the melt temperature of the polymers. Subsequently, the surface topography of the moulded parts is evaluated by digital 3D laser-scanning microscopy. The influence of the moulding parameters and the coating of the mould insert on the moulding accuracy and the demoulding behaviour are being analysed. It is shown that micro structures created by ultra-short pulse laser ablation can be successfully replicated in a variothermal moulding process. Due to the mould coating, significant improvements could be achieved in producing micro structured optical plastics components.