Phosphor Conversion Layer Mixture for Stable Deep-Red LED Color
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Solution Overview
Problem
Existing LED lamps for vehicle lighting, particularly in the red spectrum, face challenges with color saturation and luminous flux stability due to temperature fluctuations and dispersion issues in phosphor application, leading to unsatisfactory ECE-compliant color representation and reduced luminous efficacy.
Innovation Solution
A phosphor mixture comprising two phosphors with different chromaticity coordinates in the CIE standard chromaticity diagram, where one phosphor acts as a filter for the other, enhancing color saturation and stability by absorbing and re-emitting light in specific wavelength ranges, thereby maintaining luminous flux and achieving deeper red hues without significant hardware or software interventions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a single phosphor is used in the conversion layer to emit red light, then the luminous flux can be maintained at a certain level, but the color saturation remains insufficient and the color locus does not reach the outer spectral color line in the CIE chromaticity diagram
Solution Approach 1:
The patent combines multiple phosphors (including red-emitting phosphors and yellow-emitting phosphors) in the conversion layer to create a composite phosphor system. This merging of different phosphor materials allows the system to achieve both adequate luminous flux and improved color saturation, with the color locus approaching the outer spectral color line in the CIE chromaticity diagram while maintaining stable color properties.
2Stability of the object's composition
If the conversion layer thickness is increased to improve color saturation, then the color locus approaches the outer spectral color line, but the luminous flux is negatively affected
Solution Approach 1:
The patent optimizes the thickness parameter of the conversion layer to a specific range (30 μm to 70 μm) that balances color saturation and luminous flux. By carefully controlling this parameter, the system achieves adequate color saturation with the color locus approaching the outer spectral color line while maintaining acceptable luminous flux levels, avoiding the trade-off that would occur with excessive thickness.
3Illumination intensity
If garnet-colored phosphors are used to achieve high luminous efficacy, then the luminous flux is improved, but the color saturation is comparatively low and the color locus lies in the garnet range rather than deeper red
Solution Approach 1:
The patent employs composite phosphor materials including red-emitting phosphors (such as Sr2Si5N8:Eu2+, SrSi2O2N2:Eu2+) combined with yellow-emitting phosphors (such as YAG:Ce3+, Lu3Al5O12:Ce3+). This composite material system achieves both high luminous efficacy and deep red color saturation, with the color locus reaching the outer spectral color line, overcoming the limitations of single garnet-colored phosphors.
4Stability of the object's composition
If the conversion layer thickness is increased to achieve higher conversion, then the color saturation improves, but the manufacturing precision requirements increase and process complexity increases
Solution Approach 1:
The patent sets the conversion layer thickness within an optimized range of 30 μm to 70 μm, which achieves adequate color saturation without requiring excessive thickness control precision. This parameter optimization reduces the stringency of manufacturing precision requirements while still achieving the desired color performance, making the production process more feasible.
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 phosphor mixture achieves higher color saturation and stability, maintaining luminous flux while reducing sensitivity to temperature and dispensing weight fluctuations, allowing for precise target color definition and cost savings through optimized material usage and reduced layer thickness.
Implementation Method 1
The first phosphor is adapted to emit light of a first unsaturated color when irradiated with light from the semiconductor light source
Implementation Method 2
The second phosphor is adapted to emit light of a second unsaturated color when irradiated with light from the semiconductor light source
Implementation Method 3
the second phosphor is adapted to absorb and filter light in a region of the first wavelength range that extends adjacent to the lower boundary thereof
Data Source
AI summary
A phosphor composition may include first and second phosphors configured to emit light of a first and a second unsaturated color, respectively. The first unsaturated color may be associated with a first position in a CIE standard color chart adjacent to and above a position of a selected target color of the phosphor composition in the CIE standard color chart. The second unsaturated color may be associated with a second position in a CIE chromaticity diagram adjacent to and below the position of the selected target color of the phosphor composition in the CIE chromaticity diagram. Thereby, the position of the selected target color of the phosphor composition in the CIE chromaticity diagram may be located in an area defined by corner positions R=(cx; cy) given by R1=(0.645; 0.335), R2=(0.665; 0.335), R3=(0.735; 0.265), and R4=(0.721; 0.259).