Oxyfluoride Garnet Phosphor for LED Color Rendering
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Solution Overview
Problem
Current green-emitting phosphors in solid state lighting systems, such as those using YAG, suffer from poor color rendering properties and high color temperature, failing to accurately imitate natural light and provide improved red-green contrast.
Innovation Solution
A lighting apparatus employing a phosphor blend comprising an oxyfluoride garnet phosphor with a peak emission in the 530-580 nm range, combined with a red-emitting phosphor, which absorbs blue LED radiation and emits green light, offering improved color rendering and red-green contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If YAG phosphor is used in white LEDs, then the lighting system achieves high luminosity, but the color rendering properties deteriorate and red-green contrast is poor
Solution Approach 1:
The patent employs a composite phosphor system consisting of YAG:Ce phosphor combined with secondary phosphors (such as red-emitting CaAlSiN3:Eu2+ or green-emitting beta-SiAlON:Eu2+). This composite approach allows the system to maintain the high luminosity contribution from YAG while adding spectral components that improve color rendering and red-green contrast, thereby resolving the contradiction between brightness and color quality.
2Illumination intensity
If YAG phosphor is used, then high luminosity is achieved, but color temperature becomes too high and natural light imitation fails
Solution Approach 1:
The patent adjusts the color temperature of the lighting system by modifying the phosphor composition ratios and selecting phosphors with appropriate emission characteristics. By combining YAG:Ce with secondary phosphors having different emission wavelengths and intensities, the system can tune the overall color temperature to achieve a more natural light appearance while preserving high luminosity output.
3Device complexity
If conventional phosphors are used, then device simplicity is maintained, but color rendering and red-green separation are insufficient
Solution Approach 1:
The patent introduces a composite phosphor system that combines YAG:Ce with secondary phosphors (red-emitting CaAlSiN3:Eu2+ or green-emitting beta-SiAlON:Eu2+). This composite approach enhances color rendering and red-green separation by adding specific spectral components, while the implementation remains relatively simple through co-firing or co-deposition processes, thus achieving improved color quality without excessive complexity increase.
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 oxyfluoride garnet phosphor blend enhances color rendering and red-green contrast, providing better illumination quality and maintaining emission intensity across a range of temperatures, with improved red-green separation and luminosity.
Implementation Method 1
a phosphor material that is radiationally coupled to the light source, the phosphor material comprising a blend of: an oxyfluoride phosphor having a peak emission in a wavelength range from 530 nanometers to 580 nanometers
Implementation Method 2
which absorbs blue LED radiation and emits green light
Data Source
Figure 1~2
Figure 3
AI summary
A lighting apparatus having a phosphor material radiationally coupled to a light source is presented. The phosphor material includes a green emitting phosphor composition of general formula I: R3-x-zMxCezT5-yNyO12-x-yFx+y; where 0≤x<3.0; 0≤y<5.0, 0<z≤0.30; and if x=0, then y>0 or if y=0, then x>0; R is Y, Tb, Gd, La, Lu or a combination thereof; T is Al, Sc, Ga, In or combinations thereof; M is Ca, Sr, Ba or a combination thereof; N is Mg, Zn or a combination thereof. The phosphor composition of formula I may be combined with an additional phosphor to generate white light.