Colour shift in remote phosphor based LED products

In this paper, the thermal stability and the colour shifting of remote phosphor plates, made from Bisphenol-A polycarbonate (BPA-PC), are studied. In this study, the remote-phosphor and lens of BPA-PC samples of 3 mm thickness were thermally aged at temperature range 100 to 140 ^oC. Results show that thermal ageing leads to a significant decrease in the luminous flux and chromatic properties of plates. Lumen depreciation up to 30% reduction is extrapolated to temperatures lower than 100 °C. It is shown that the lifetime, defined as 30% lumen depreciation at 40 °C, is around 35 khrs. It is also shown that by increasing the temperature, the reaction rate becomes faster, inferring that lumen depreciation takes place at shorter time. Results also illustrate the colour shifting of white light towards yellow region.