Colour shift and mechanism investigation on the PMMA diffuser used in LED-based luminaires |
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| Affiliation: | 1. Beijing Research Center, Delft University of Technology, Beijing, China;2. Delft University of Technology, EEMCS Faculty, Delft, The Netherlands;3. State Key Laboratory of Solid State Lighting, Changzhou, China;4. Department of Mechanical Engineering, Lamar University, Beaumont, TX 77710, USA;5. Delft University of Technology, Industrial Design Engineering Faculty, Delft, The Netherlands;6. Materials Innovation Institute (M2i), Delft, The Netherlands;7. College of Mechanical and Electrical Engineering, Hohai University, Changzhou, China;8. Institute of Semiconductors, Chinese Academy of Sciences, Haidian, Beijing, China;1. College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, China;2. Nantong Friendly New Materials Co., Ltd, Nantong 226000, China;3. Department of Physics and Interdisciplinary Program of Biomedical, Mechanical & Electrical Engineering, Pukyong National University, Busan 608-737, Republic of Korea;1. Global Frontier Center for Multiscale Energy Systems, Seoul National University, Seoul 151-744, Republic of Korea;2. Rare Isotope Science Project, Institute for Basic Science, Daejeon 305-811, Republic of Korea;1. School of Materials Science and Engineering, Fujian University of Technology, 3 Xueyuan Road, Fuzhou 350108, PR China;2. Fujian Provincial Key Laboratory of Advanced Materials Processing and Application, 3 Xueyuan Road, Fuzhou 350108, PR China;1. Departamento de Física, Universidade Federal de Pernambuco, 50670-901 Recife, PE, Brazil;2. Grupo de Física da Matéria Condensada, Núcleo de Ciências Exatas – NCEx, Campus Arapiraca, Universidade Federal de Alagoas, 57309-005 Arapiraca, AL, Brazil;3. Grupo Física de Materiais, Instituto de Física, Universidade Federal de Goiás, 74001-970 Goiânia, GO, Brazil |
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| Abstract: | PMMA material is widely used in LED-based luminaires due to several advantages such as excellent optical transparency, durability against radiation, surface hardness (scratch free), rigidity and strength and can be completely recycled. However, few studies have been reported on the colour shift and failure mechanisms caused by this type of material. This paper experimentally investigated PMMA materials with different aging conditions. The following conclusions could be drawn. (1) Discolouration was not observed for any sample subjected to aging of 85 °C for 5000 h, or with additional blue light irradiation for 5000 h, or with additional humidity of 85%RH for 5000 h, or even with aging of 100 °C for 3000 h. (2) The specimen subjected to aging of 150 °C for 360 h has a surface discoloration and has a significant wavelength dependent degradation in the transmission spectrum caused by oxidation. The specimen with aging of 100 °C for 3000 h has a less oxidation, although no significant transmission spectrum reduction was observed. (3) Using such aged specimen as a diffuser mounted on a LED-based luminaire, the radiant flux peak intensity in the blue light area has a more severe reduction than that in the yellow light area, which results in a reduction of the radiant flux intensity ratio of blue light to yellow light and hence induces the colour shift to yellow. The colour shift investigated is 0.005, very close to the general failure criterion of 0.007, while the lumen decay is 10.2%, far less than the failure criterion of 30%. |
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| Keywords: | Colour shift PMMA Solid state lighting LED-based luminaire Infrared absorption spectroscopy |
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