以螢光粉為關鍵材料的白光LED 正在增加其影響力，尤其當在2014 年3 月Cree 公司發表在 350 mA 的驅動電流下，高功率白光LED 的Luminous efficacy 可達到驚人的303 lm/W 時，白光LED 全面取代各式光源，而成為一般照明的光源時代已然來臨，但是隨著發光效率屢創新高，一項潛藏的 藍光溢漏危害卻不為人所知。 本計畫是一個三年期的計畫，是建立在研究團隊已歷時三年研究的LED 藍光溢漏的基礎上。 我們發現當白光LED 效率越好之時，在可接受的亮度下，可以承受的溫度也越高，但是螢光粉受熱 所造成個熱衰，是目前無法避免的問題。而造成的影響是當LED 因老化而過熱時，其色溫會持續升 高，而終至於藍光與黃光比值過度增加，形成藍光溢漏的危害。本計畫基於與法國CNRS 研究中心的 長期合作，在經過多種試驗後，找到一種奈米纖維素材料，可以有效地在老化的LED 過熱時產生變 黑的化學變化來使LED 的亮度快速地衰減，進而讓使用者能夠知道要將該光源置換，並將此種裝置 取名為”光學保險絲”。本計畫將於第一年持續對該材料進行性能的瞭解，同時研究可能幾種封裝之熱 場分布；第二年將進行該材料應用於實際LED 的封裝，同掌握到最佳的置放點，使LED 在正常使用 時期發光亮度不受到影響；第三年將完整開發出此製程，同時引入法國團隊優化後的材料，最終將正 式對外技術移轉；第三年同時將設計主動式的防藍光溢漏之電路，藉由電子元件溫度效應來輔助LED 達到過熱保護目的。本技術的基礎專利已經布局，因此研究對於我國LED 產業在爭取未來的國際競 爭上具有優勢。 ;Phosphor-converted white LED has increased its impact to general people, especially when CREE announced the highest luminous efficacy of 303 lm/W@350mA in 2014. Obviously, white LED will become the major light source in general lighting. However, the extremely high luminous efficacy could induce blue light leakage hazard. Here we propose a 3-year project, which is based on the previous study for preventing blue light leakage in white LEDs. We discovered that a potential hazard occurs when serious thermal quenching for phosphor as the temperature is higher than the set value in a normal operation duration. The high temperature will cause degradation of phosphor, so that the correlated color temperature will increase, and so does the ratio between the blue and yellow light. This will cause blue light leakage. This project is based the collaboration achievement on this topic with CNRS in France. Through the 3-year study, we found a new material nanocellulose, which could become darkening to suppress the brightness of a white LED when it is over heated due to aging. Thus the user can understand to replace the disabled white LED. The element has a new name of “optical fuse”. In the first year, we will keep studying the property of the nanocellulose, and making precise characterization. Also, we will study the temperature distribution for several major packaging structures. In the second year, the nanocellulose will be precisely introduced at the right position to avoid over heated at the normal operation duration so that the brightness of the LED will not affected in this stage. In the third year, we will start to design active optical fuse with introducing appropriate electronic element with suitable thermal effect to protect the user from the aging white LED. The essential patent has been filed so that the success of the development of this technology will benefit Taiwan industry.
