Colour shift and mechanism investigation on the PMMA diffuser used in LED-based luminaires

Journal article (2016)

Authors

G. Lu Beijing Delft Institute of Intelligent Science and Technology , State Key Laboratory of Solid State Lighting, Electronic Components, Technology and Materials -

W.D. van Driel Beijing Delft Institute of Intelligent Science and Technology , Electronic Components, Technology and Materials -

Xuejun Fan State Key Laboratory of Solid State Lighting, Lamar University

M. Yazdan Mehr Material Innovation Institute (M2i), Electronic Components, Technology and Materials -

Jiajie Fan Hohai University, State Key Laboratory of Solid State Lighting

Cheng Qian Chinese Academy of Sciences

K.M.B. Jansen Emerging Materials -

Kouchi Zhang Chinese Academy of Sciences, Electronic Components, Technology and Materials -

Research Group

Electronic Components, Technology and Materials () (TU Delft)

Solid state lighting PMMA Colour shift LED-based luminaire Infrared absorption spectroscopy

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Published Date

2016

Language

English

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Faculty

Electrical Engineering, Mathematics and Computer Science

Department

Microelectronics

Research Group

Electronic Components, Technology and Materials

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%.