Angular color uniformity enhancement of white light-emitting diodes by remote micro-patterned phosphor film

Angular color uniformity (ACU) is a key factor used to evaluate the light quality of white-light emitting diodes (LEDs). In this study, a novel double remote micro-patterned phosphor film (double RMPP film) was used to enhance the ACU of a remote phosphor (RP) down-light lamp. A conventional RP film and remote phosphor film with single micro-patterned film (single RMPP film) also were examined for comparison. The angular correlated color temperature (CCT) distributions and the optical performance of the films were experimentally measured. The measurement results showed that double RMPP film configuration exhibited better color uniformity with a CCT deviation of only 441 K, compared with 556 K for the single RMPP film configuration and 1390 K for the RP film configuration. A simulation based on FDTD and ray tracing combined method also confirmed the ACU improvement. In addition, compared with the conventional RP film, the luminous efficiency of single and double RMPP film configurations was increased by 6.68% and 4.69%, respectively, at a driving current of 350 mA. The enhancement of the ACU and luminous efficiency are due to the scattering and mixing effect of the micro-patterned film. Moreover, the double RMPP film configuration had better CCT stability at different currents than the other two configurations. The results demonstrated the effectiveness and superiority of double RMPP film in white LED applications. (C) 2016 Chinese Laser Press