| As a new generation of solid-state lighting device, white Light-Emitting Diode(LED) has come into people’s life because of the advantages which white LED owned such as high efficiency,energy saving and environmental protection. This reason makes white LED have huge potential. The ways of making White LED can be roughly divided into three kinds: considering factors such as ratio of performance and cost at present, a common use is blue LED chip coated with yellow phosphors. Coating layer with fluorescent powder is one of the most important steps in the whole process of making LED.In this paper, the research direction is the study of phosphor coating technology.An important reference of evaluating the pros and cons of a phosphor coating technology is LED luminous efficiency and uniformity of space temperature distribution. Given the phosphor coating technology, this paper is based on the original electrophoresis coating technology,combining electrophoresis coating technology and self-adaptive coating technology innovativily which purpose is to improve the LED luminous efficiency and space distribution uniformity of coating color temperature of original electrophoresis coating technology.In this paper, the main work is concluded the experimental plan of the modified electrophoretic deposition coating structure of white LED phosphors and the longitudinal and transverse analysis on the finished product after process, discussing the change of luminous flux, luminous efficiency and the color temperature spatial distribution uniformity after each step of LED chip.firstly, transparent conductive coating is indispensable in the electrophoresis coating technology, and this experiment adopts the ATO as transparent conductive material, the transmission of ATO has a more significant improvement than ITO’s. Through the analysis on blue LED chips of coated with and without ATO about relative spectrum, absolute spectrum and spatial temperature distribution, ATO layer has no effect on the LED color temperature distribution, at least no effect in this experiment within the scope of the precision of experimental apparatus.However,the luminous flux and luminous efficiency of LED chips coated with ATO is 75.5% of the original blue LED chips.And, the reason of the difference of the spectral data between the spectrometer and the integrating sphere is that two instrument’s precisions are different from each other and both not enough.Secondly, spraying a layer of silica gel layer after the first step Electrophoretic Deposition(EPD), luminous efficiency improved; Again after self-adaptive coating technology,the luminous efficiency decreased; Finally, after glue encapsulation, luminous efficiency improved.Then changing rule of the luminous flux and luminous efficiency is the same.Again,silica gel layer can indeed improve the blu-ray extraction rate and rise color temperature,and the extraction rate is positively depended on the thickness of the silicone, while silicone cannot guarantee to improve the uniformity of color temperature because the sensitivity of temperature is different in different temperature range. The self-adaptive process step in the whole process of new tech indeed has played an important role in fixing space color temperature uniformity, but also can make up for the unstable effect of errorfrom the silica gel layer.Then, the ratio of wavelength corresponding to the peak vaule in shortwave region to the one in longwave region remains 0.8 unchanged. The larger the ratio,the higher the CCT,and the ratio from 4500 K to 4600 K is about 1.Finally,comparison about luminous efficiency and space temperature distribution of samples in new process and the samples in original EPD process, it is known that: luminous efficiency than original EPD technology increased by 6.17%, and the standard deviation was reduced by 3.17%. When LED color temperature is about 5000 k, the standard deviation of color temperature distribution decreased by 17.67%. |
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