White Light Emitting Device Orange Green Phosphor Mixture
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Solution Overview
Problem
Conventional white Light Emitting Diode (LED) devices using blue and yellow phosphors have limited wavelength shift range, resulting in restricted selection of blue LED peak wavelengths for achieving high-quality white light, which hinders the realization of pure white light with optimal chromaticity coordinates.
Innovation Solution
A white light emitting device utilizing a combination of orange and green phosphors with specific compositions, dispersed in an encapsulant with a blue LED, expands the peak wavelength range of the blue LED from 420 to 480 nm by adjusting the mixing ratio of the phosphors, allowing for a broader selection of blue LEDs for achieving white light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional yellow phosphors (YAG:Ce, TAG:Ce, silicate phosphor) are used with blue LED, then white light can be generated, but the wavelength shift range is limited and the selection of blue LED peak wavelengths is restricted
Solution Approach 1:
The invention divides the single yellow phosphor into two separate phosphors: yellow phosphor and green phosphor. Each phosphor has optimized emission characteristics, and their combination expands the overall wavelength coverage while maintaining high efficiency at each peak wavelength region.
Solution Approach 2:
The patent uses a composite phosphor system combining yellow phosphor (e.g., YAG:Ce, TAG:Ce) and green phosphor (e.g., beta-sialon:Eu, SrSi2O2N2:Eu). This composite approach leverages the strengths of each phosphor material to achieve broader wavelength adaptability without sacrificing emission efficiency.
2Adaptability or versatility
If phosphor composition is adjusted to shift wavelength, then peak wavelength can be changed, but light emission efficiency degrades in the corresponding wavelength region
Solution Approach 1:
Instead of adjusting a single phosphor's composition to cover a broad range (which degrades efficiency), the invention segments the emission spectrum into multiple bands handled by different phosphors. Each phosphor operates at its optimal composition for its specific emission band, maintaining high efficiency.
Solution Approach 2:
The patent changes the parameters of the phosphor system by introducing multiple phosphors with different emission characteristics rather than modifying a single phosphor's composition. This allows independent optimization of each phosphor's emission peak while achieving overall spectral coverage.
3Illumination intensity
If Garnet-based or silicate-based yellow phosphors are used, then yellow light emission is achieved, but the shift range is very small which limits the blue LED wavelength selection
Solution Approach 1:
The invention segments the phosphor system into yellow phosphor for the yellow region and green phosphor for the green region. This segmentation allows each phosphor to be optimized for its specific region, enabling broader blue LED wavelength selection while maintaining strong yellow light emission.
Solution Approach 2:
By creating a composite phosphor system with yellow and green phosphors, the patent achieves both strong yellow light emission (from the yellow phosphor) and expanded wavelength adaptability (from the combination with green phosphor covering different spectral regions).
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
This approach significantly expands the selection range of blue LED peak wavelengths, enabling the production of high-quality white light with improved chromaticity coordinates by adjusting the types and mixing ratios of orange and green phosphors, resulting in a wider light emission spectrum.
Implementation Method 1
a blue light emitting diode
Implementation Method 2
The phosphor is excited by the blue light emitted from the LED, and thereby emits yellow light
Implementation Method 3
a mixture of orange phosphor and green phosphor disposed above the blue light emitting diode
Data Source
AI summary
A white light emitting device capable of expanding the wavelength range of a blue LED used for realizing white light. The white light emitting device according to the present invention includes a blue LED and a mixture of orange phosphor and green phosphor disposed above the blue LED.