Abstract
This paper reports the fabrication of double-sided micro-lens arrays using a UV injection molding process. The apparatus for UV injection molding is designed and implemented. Because the double-sided micro-lens array is fabricated using a UV-curable resin, the molds must be transparent. An alignment system is also required to align the cavities. In preparing the transparent molds, the cavities for the concave micro-lens and the alignment marks are first machined on the aluminum block. Using electroforming and hot embossing, transparent polycarbonate (PC) molds that have cavities for the MLAs and the alignment marks are fabricated. The PC molds are mounted on the UV injection molding apparatus using a pneumatic clamp. A real-time optical alignment system that comprises a CCD and an X-Y table is used to align the marks in the upper and lower molds. After alignment, the UV-curable resin is injected into the molds using a pneumatic dispenser. When the resin is cured with UV light, a double-sided micro-lens array is fabricated. The cycle time is 45 s. The respective degrees of replication for a convex and a concave micro-lens array are 99.74 % and 99.00 %. The respective standard deviation values for the diameter and the height are 1.3 μm, and 1.5 μm. The optical properties of the double-sided micro-lens array are measured. The average effective focal length is 1.686 mm, with a standard deviation of 0.007 mm, which demonstrates good formability and uniformity. Using the fabricated micro-lens array, the 1.2 mm diameter of the original light source is reduced to a 50 μm spot diameter. The images of an “A” pattern are complete and clear. This study demonstrates that a UV injection molding process that uses transparent PC molds can be used to fabricate a micro-lens array and other double-sided microstructures.
References
Bender, M., Otto, M., Hadam, B., Vratzov, B., Spangenberg, B. and Kurz, H., “Fabrication of Nanostructures Using a UV-Based Imprint Technique”, Microelectron. Eng., 53, 233–6 (2000) 10.1016/S0167-9317(00)00304-XSearch in Google Scholar
Chang, C.-Y., Yang, S.-Y. and Chu, M.-H., “Rapid Fabrication of Ultraviolet-Cured Polymer Micro-Lens Arrays by Soft Roller Stamping Process”, Microelectron Eng., 84, 355–361(2007) 10.1016/j.mee.2006.11.004Search in Google Scholar
Chang, C. Y., Yang, S. Y. and Sheh, J. L., “A Roller Embossing Process for Rapid Fabrication of Micro-Lens Arrays on Glass Substrates”, Microsyst. Technol., 12, 754–759 (2006) 10.1007/s00542-006-0103-5Search in Google Scholar
Huang, P.-H., Huang, T.-C., Sun, Y.-T. and Yang, S.-Y., “Fabrication of Large Area Resin Micro-Lens Arrays Using Gas-Assisted Ultraviolet Embossing”, Opt. Express, 16, 3041–3048, (2008)PMid:18542390; 10.1364/OE.16.003041Search in Google Scholar
Ji, H.-S., Kim, J.-H. and Kumar, S., “Electrically Controllable Micro-Lens Array Fabricated by Anisotropic Phase Separation from Liquid-Crystal and Polymer Composite Materials”, Opt. Lett., 28, 1147–11479 (2003)PMid:12879936; 10.1364/OL.28.001147Search in Google Scholar
Lee, C. L., Choi, H. W., Gu, E., Dawson, M. D. and Murphy, H., “Fabrication and Characterization of Diamond Micro-Optics”, Diamond Relat. Mater., 15, 725–728 (2006) 10.1016/j.diamond.2005.09.033Search in Google Scholar
Lee, B.-K., Kim, D.S. and Kwon, T. H., “Replication of Micro-Lens Arrays by Injection Molding”, Microsyst. Technol., 10, 531–535 (2004) 10.1007/s00542-004-0387-2Search in Google Scholar
Nieto, D., Vara, G., Diez, J. A., O’Connor, G. M., Arines, J. and Gómez-Reino, C., “Laser-Based Microstructuring of Materials Surfaces Using Low-Cost Micro-Lens Arrays”, J. Micro/Nanolith. MEMS MOEMS, 11, 1–7, 023014 (2012)10.1117/1.JMM.11.2.023014Search in Google Scholar
Ogata, S., Ishida, J. and Sasano, T., “Optical Sensor Array in an Artificial Compound Eye”, Opt. Eng., 33, 3649–3655 (1994) 10.1117/12.179889Search in Google Scholar
Ong, N. S., Koh, Y. H. and Fu, Y. Q., “Micro-Lens Array Produced Using Hot Embossing Process”, Microelectron Eng., 60, 365–379 (2002) 10.1016/S0167-9317(01)00695-5Search in Google Scholar
Sun, H., Wang, X., Xiong, Y., Liu, G. and Wang, K., “Fabrication of Micro-Lens Based on Overplating in Electroforming”, J. Micromech. Microeng., 26, 055007 (2016) 10.1088/0960-1317/26/5/055007Search in Google Scholar
Wei, M.-K., Su, I.-L., Chen, Y.-J., Chang, M., Lin, H.-Y. and Wu, T.-C., “The Influence of a Micro-Lens Array on Planar Organic Light-Emitting Devices”, J. Micromech. Microeng., 16, 368–374 (2006) 10.1088/0960-1317/16/2/022Search in Google Scholar
Xie, P., Chang, L., Song, L., Cai, T., Ding, Y. and Yang, W., “The Research of UV Curing Injection Molding”, AIP Conf., 1664, 110005 (2015) 10.1063/1.4918480Search in Google Scholar
Zhou, L., Dong, X.-X., Lv, G.-C., Chen, J. and Shen, S., “Fabrication of Concave Micro-Lens Array Diffuser Films with a Soft Transparent Mold of UV-Curable Polymer”, Opt. Commun., 342, 167–172 (2015) 10.1016/j.optcom.2014.12.071Search in Google Scholar
Zhu, X., Chen, H., Zhu, L., Wang, H. and Zhang, W., “Fabrication of Curved Micro-Lens Array Using a Drop-On-Demand Droplet Generator and Polydimethylsiloxane Replica Mold”, Opt. Eng., 53, 1–9 (2014) 10.1117/1.OE.53.11.117109Search in Google Scholar
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