高演色性白光發光二極體之研究

The research on high color rendering index white light light-emitting diode

林蘇逸(Su-Yi Lin)

指導教授 ： 李允立

國立臺灣大學/電機資訊學院/光電工程學研究所/碩士(2007年)

https://doi.org/10.6342/NTU.2007.02618

摘要

在過去LED的主要市場為單色光LED，其應用是在產品上作為指示光源。直至1996年日本日亞化學公司發展出以藍光LED搭配黃光螢光粉(YAG)製作出高效率白光LED，人們才對於白光LED照明時代的來臨的看見了一線曙光。隨著藍光LED晶片發光效率的提升，現今高效率白光LED的流明效率已經達到了90 lm/W已超出一般常用照明的流明效率，白熾燈泡約20lm/W與螢光燈管約70~80 lm/W。照明光源的功用除了顯示被照物體的形狀以及大小外，而呈現物體真實色彩的能力更是評估一個照明光源的重要指標，定義這能力好壞的標準就是所謂的演色性(color rendition)。常見的白光LED其CRI值約在40~70，對照明光源而言這樣的演色性表現是不夠的。

本研究主旨在於探討如何以模擬方式預估由藍光LED晶片激發多種螢光粉所製作出高演色性白光LED光學性質，藉由螢光粉塗布上改良增進模擬結果的精確度。由模擬方式預估高演色性白光LED頻譜組合，利用多層螢光粉塗布方式製作出CCT 3000K CRI 96與CCT 6500K CRI 87.6的高演色性白光LED。整體而言模擬與實驗結果相似，相信此模擬方式可評估多種螢光粉組合對於白光LED光學性質影響，藉由多層塗布方式可減少螢光粉放光在不同螢光粉間相互吸收效應。

在多色LED混成高演色性白光光源研究方面，以高斯(Gaussion)分布模擬LED發光頻譜。由溫度對LED晶片影響出發，探討當LED受熱時發光強度衰減、主波長紅移與半高強度寬增加等現象，利用適當晶片選擇方式製混成穩定高演色性LED白光光源。模擬結果得知在最佳化情況下四色LED白光光源CRI比三色LED白光光源高約10，對於溫度的影響四色LED也比三色LED模擬結果來的穩定，因此相信四色LED比起三色LED白光光源更適合做為照明光源。

關鍵字

發光二極體 ； 螢光粉 ； 演色性 ； 白光 ； 照明

並列摘要

The major market of the light-emitting diode was the monochromatic light LED in the past. The application of LED was the indicative light on the products. Until the Nichia chemical company in Japan developed the high efficiency white light LED which was combined the blue LED chip with the yellow phosphor (YAG) in 1996, people started to expect the coming of the white light LED illuminative period. With the improving of the blue LED chip’s efficiency, the luminous efficiency of the high power white light LED is 90lm/W which is higher than the fluorescent lamp. The functions of the illumination are showing the shape, color and size of the object. The ability of showing the true colors is an important assize to estimate an illumination, and the color rendering index (CRI) is a stander to estimate this ability. The CRI of the general white light LED is about 50~70, and it’s not enough for the illumination.

This study aims at discuss on the simulation of the high CRI white light LED which was combined the blue chip with multi-color phosphor, and calculate the optical properties of the high CRI white light LED. The accuracy of simulation results is improved by improving the phosphor daub. This study simulates the spectra of high CRI white light LEDs and makes the high CRI white light LEDs with the CCT 3000K CRI 96 and CCT 6500K CRI 87.6 by multi-layers phosphor daub. The simulation results and experimental results are similar. It’s believed this simulation can estimate the phosphors’ abilities to make the high CRI white light LED and the multi-layer phosphor daub can decrease the absorption of the light which is emitted by the phosphors.

In the study of high CRI white light source which is formed by multi-color LED chip, I use the Gaussion distribution to simulate the LED’s spectrum. When the temperature is rising, the thermal effects on the LED chip are the decreasing of radiation power, red shift of peak wavelength and increasing of FWHM. By choosing the LEDs combination and using the feedback system the high CRI white light source can be made. The simulation results show that the CRI of four-color LED white light source is higher the three-color one and the four-color LED white light source with the smaller CRI shift when temperature rising. It’s is believed that four-color LED white light sources is a better illumination than three-color one.

並列關鍵字

LED ； phosphor ； CRI ； color rendering index ； white light ； illumination

參考文獻

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