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Article

Laser-Assisted Thermal Imprinting of Microlens Arrays—Effects of Pressing Pressure and Pattern Size

Department of Mechanical Engineering, Graduate School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan
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Author to whom correspondence should be addressed.
Materials 2019, 12(4), 675; https://doi.org/10.3390/ma12040675
Received: 30 January 2019 / Revised: 19 February 2019 / Accepted: 22 February 2019 / Published: 25 February 2019
Polymer films with nano- or microstructured surfaces have been widely applied to optical devices, bioplates, and printed electronics. Laser-assisted thermal imprinting (LATI), in which a laser directly heats the surfaces of a mold and a thermoplastic polymer, is one of the high-throughput methods of replicating nano- or microstructures on polymer films. Only the surfaces of the mold and polymer film are heated and cooled rapidly, therefore it is possible to replicate nano- or microstructures on polymer films more rapidly than by using conventional thermal nanoimprinting. In this study, microlens arrays (MLAs) were replicated on polymethylmethacrylate (PMMA) films using LATI, and the effects of the pressing pressure (10−50 MPa) and the pattern size (33- and 5-μm pitch) of the MLA on the filling ratio were investigated by analyzing a microlens replicated using different laser-irradiation times (0.1−2 ms). The filling ratio increased with increasing pressing pressure and laser-irradiation time in the replication of MLAs with varying sizes, while the flow of the PMMA varied with the pressing pressure and laser-irradiation time. It was found that during filling, the shape of the polymer cross-sectional surface demonstrated a double and single peak in the 33- and 5-μm-pitch patterns, respectively. This was because the depth of the heated area in the 33-μm-pitch pattern was smaller than the pattern size, whereas that of the 5-μm-pitch pattern was comparable to (or larger) than the pattern size. View Full-Text
Keywords: laser-assisted thermal imprinting; pressure; pattern size; thermoplastic polymer; microlens array laser-assisted thermal imprinting; pressure; pattern size; thermoplastic polymer; microlens array
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MDPI and ACS Style

Nagato, K.; Yajima, Y.; Nakao, M. Laser-Assisted Thermal Imprinting of Microlens Arrays—Effects of Pressing Pressure and Pattern Size. Materials 2019, 12, 675. https://doi.org/10.3390/ma12040675

AMA Style

Nagato K, Yajima Y, Nakao M. Laser-Assisted Thermal Imprinting of Microlens Arrays—Effects of Pressing Pressure and Pattern Size. Materials. 2019; 12(4):675. https://doi.org/10.3390/ma12040675

Chicago/Turabian Style

Nagato, Keisuke, Yuki Yajima, and Masayuki Nakao. 2019. "Laser-Assisted Thermal Imprinting of Microlens Arrays—Effects of Pressing Pressure and Pattern Size" Materials 12, no. 4: 675. https://doi.org/10.3390/ma12040675

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