Abstract
Angular color uniformity (ACU) is one of the most important optical parameters of white lighting emitting diodes (LEDs). In this paper, we proposed a kind of phosphor coating method to enhance ACU of phosphor-converted white LEDs with conventional chips by the combination of substrate structure design and phosphor dip-transfer coating. Through this method, compact and optimal phosphor layer arrangements for high ACU can be realized. Optical simulations and experiments were conducted to examine its ACU performance. Compared with conventional phosphor dispensing coating, the present method shows very high ACU performance. Extremely small angular correlated color temperature (CCT) deviations were obtained, which are less than 200K at average CCTs ranging from 4000 K to 6000 K.
Highlights
Due to their high efficiency, good chromatic performance, high reliability and environmental protection, white light emitted diodes (LEDs) present very bright prospect to become customized light sources
We proposed a kind of phosphor coating method to enhance Angular color uniformity (ACU) of phosphor-converted white lighting emitting diodes (LEDs) with conventional chips by the combination of substrate structure design and phosphor dip-transfer coating
Small angular correlated color temperature (CCT) deviations were obtained, which are less than 200K at average CCTs ranging from 4000K to 6000K
Summary
Due to their high efficiency, good chromatic performance, high reliability and environmental protection, white light emitted diodes (LEDs) present very bright prospect to become customized light sources. Owing to its low cost and simplicity, the conventional phosphor dispensing coating has been broadly applied at present In this coating method, yellow ring phenomenon usually occurs in the radiation pattern and results in bad ACU. Compared with the dispensing coating, the conformal phosphor coating shows strong attraction due to its high ACU performance in theory [8,9,10,11,12,13] This method demands that a phosphor layer with uniform thickness replicates the LED chip shape. There is a large mismatch between high-quality phosphor coating technologies and the strong application requirements for conventional LED chips
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