Photobleaching of transparent photopolymer resins for use in LED lighting optical elements

Jean Paul Freyssinier; Indika U. Perera; Nadarajah Narendran; Akila S. Udage

doi:10.1117/12.2676984

6 October 2023 Photobleaching of transparent photopolymer resins for use in LED lighting optical elements

Jean Paul Freyssinier, Indika U. Perera, Nadarajah Narendran, Akila S. Udage

Proceedings Volume PC12670, 3D Printing for Lighting; PC1267001 (2023) https://doi.org/10.1117/12.2676984
Event: SPIE Optical Engineering + Applications, 2023, San Diego, California, United States

Abstract

Photopolymer 3D printing of optically clear resins is a promising technology for producing custom optical elements for general illumination. However, the transparency of the final 3D-printed part may depend on secondary processes. Residual photoinitiator can result in a yellowish tint that can be photobleached after exposure of the 3D-printed part to a light source. The study was designed to understand the tradeoff between the spectral characteristics of the light source used for the photobleaching and the irradiance to which test samples were exposed on the rate of photobleaching. A total of 14 samples were tested at room temperature for 120 minutes under a combination of three light sources (xenon, phosphor converted white LED, and direct emission blue LED), and up to five irradiance levels for each source in the range 0.0025 to 0.2238 W/cm². The results showed that for the white LED, irradiance can increase the magnitude of the photobleaching. In this study, the maximum chromaticity shift was equivalent to a 4-step MacAdam ellipse. These results seem to indicate that it is possible to expedite photobleaching by increasing the irradiance, although more testing is necessary to find an optimum value. The results for the blue LED tests (peak wavelength 450 nm) showed that this spectrum can be as effective or slightly better at photobleaching than the white LED tested for the same total irradiance. The samples exposed to the xenon light source resulted in increased yellowish tint, presumably because of additional oxidation on the surface of the sample. For these samples irradiated with the xenon lamp, the tint increased with increasing irradiance.

Conference Presentation

Citation Download Citation

Jean Paul Freyssinier, Indika U. Perera, Nadarajah Narendran, and Akila S. Udage "Photobleaching of transparent photopolymer resins for use in LED lighting optical elements", Proc. SPIE PC12670, 3D Printing for Lighting, PC1267001 (6 October 2023); https://doi.org/10.1117/12.2676984

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