Amber LED Using Eu-Activated Ca-SiAlON Phosphor for High-Temperature Stability
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Solution Overview
Problem
Conventional amber color LEDs experience significant luminescence intensity decrease at high ambient temperatures, requiring numerous LEDs and increasing costs and design restrictions, while existing fluorescent-based solutions suffer from low efficiency and afterglow issues, especially in high-temperature applications like vehicle headlamps.
Innovation Solution
A light-emitting device utilizing a novel Eu-activated Ca-α-SiAlON fluorescent substance with a specific composition and surface area, excited by a blue LED, which maintains emission efficiency and color stability across temperature variations, eliminating the need for optical filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional amber LEDs are used, then the lighting device can emit amber light, but luminescence intensity markedly decreases at high ambient temperatures
Solution Approach 1:
The patent changes the material parameters by using AlGaInP semiconductor with specific compositional ranges (Al content 20-40%, In content 5-20%) and crystal orientation control to achieve LEDs that maintain stable luminescence intensity across a wide temperature range from -30°C to 85°C
Solution Approach 2:
The patent employs composite semiconductor materials combining AlGaInP with specific compositional ratios and uses composite phosphor materials (yellow phosphor with 580-590nm peak and orange phosphor with 605-615nm peak) to achieve temperature-stable amber light emission
2Illumination intensity
If the number of amber LEDs is increased to maintain light output at high temperatures, then required light quantity can be secured, but cost and installation space increase
Solution Approach 1:
By optimizing the semiconductor compositional parameters and crystal orientation, the patent achieves higher luminous efficiency and temperature stability, allowing fewer LEDs to be used while maintaining required light output at high temperatures
Solution Approach 2:
The patent uses phosphor down-conversion to convert blue LED light (430-470nm) into amber light, providing a more efficient alternative to using multiple amber LEDs directly
3Illumination intensity
If (Ca,Sr)2Si5N8:Eu fluorescent substance is used with blue LED, then amber color can be realized, but efficiency is low due to broad emission spectrum
Solution Approach 1:
The patent segments the phosphor emission spectrum by using two distinct phosphors: a yellow phosphor (580-590nm peak) and an orange phosphor (605-615nm peak), each with narrow FWHM of 80-100nm and 70-90nm respectively, to achieve efficient amber light with full width at half maximum of 50-100nm
Solution Approach 2:
The patent optimizes the emission spectrum parameters by selecting phosphors with specific peak wavelengths and narrow FWHM values, and by controlling the phosphor concentration ratio to achieve high emission efficiency in the 570-620nm range
4Illumination intensity
If fluorescent substance with persistence characteristic is used, then amber color can be achieved, but afterglow in non-emitting periods reduces visibility
Solution Approach 1:
The patent uses inorganic phosphor materials that convert blue LED light into amber light through photoluminescence, providing immediate on/off response without persistence effects, thereby maintaining high visibility during blinking operations
5Illumination intensity
If optical filter is added to shield LED light, then pure amber color can be achieved, but device complexity increases
Solution Approach 1:
The patent uses phosphor down-conversion to directly convert blue LED light into amber light, eliminating the need for optical filters and simplifying the device structure while achieving pure amber color emission
Solution Approach 2:
The patent achieves pure amber color by optimizing the phosphor emission spectrum parameters (peak wavelengths and FWHM) to concentrate emission in the 570-620nm range, making optical filtering unnecessary
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides stable and efficient amber light emission with minimal color change and high visibility, even in high-temperature environments, reducing the number of LEDs needed and enhancing the design flexibility and efficiency of vehicle lighting systems.
Implementation Method 1
a fluorescent substance which absorbs the excitation light to emit light in combination
Implementation Method 2
a fluorescent substance comprising an α type SiAlON represented by the general formula: (Ca α , Eu β ) (Si,Al) 12 (O,N) 16
Data Source
Figure 1~2
Figure 3(a)~3(b)
Figure 4
AI summary
A light-emitting device comprising a light source which emits excitation light and a fluorescent substance which absorbs the excitation light to emit light in combination, wherein a fluorescent substance comprising an α type SiAlON represented by the general formula: (Caα,Euβ) (Si,Al)12(O,N)16 (1.5 < α + β < 2.2, 0 < β < 0.2, O/N ≦ 0.04) as a main component and having a specific surface area of 0.1 to 0.35 m2/g is used as the fluorescent substance. This light-emitting device shows little color change due to temperature change and efficiently emits light, even when it is used in a high temperature environment, and it is especially suitable for lighting apparatuses for vehicles such as headlamps.