Ceramic Light Converter for Angle-Independent Color Point
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Phosphor-converted LEDs (pcLEDs) face issues with unstable light intensity and color point variation due to temperature changes and angle-dependent color shifts, leading to inefficient energy conversion and low color rendering index.
Innovation Solution
An arrangement using at least two electroluminescent light-sources with different primary radiation wavelengths and a ceramic light-converting element with a specific microstructure to scatter primary and secondary radiation, ensuring the color point of the mixed light is independent of the viewing angle and maintaining high efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ceramic light-converting material is used to convert blue primary radiation into red secondary radiation, then the color rendering index is improved, but energy losses increase and efficiency decreases
Solution Approach 1:
The light conversion process is segmented into multiple stages using different light-converting materials with specific bandgaps. The first material converts blue light to green/yellow, the second converts blue to red, and the third converts green to red. This segmentation allows for more efficient wavelength-by-wavelength conversion, reducing overall energy losses compared to direct blue-to-red conversion.
Solution Approach 2:
The patent employs composite light-converting materials comprising multiple phosphor compounds with different bandgaps embedded in a ceramic matrix. This composite structure enables simultaneous or sequential conversion of different wavelength regions, improving overall conversion efficiency while maintaining good color rendering properties through the combination of multiple emission spectra.
2Reliability
If multiple light-converting materials are used to produce wideband white light, then the color rendering index is improved, but the color point varies with the angle of viewing
Solution Approach 1:
The patent applies local quality by creating a layered or zoned structure where different light-converting materials are positioned in specific regions. The first light-converting material layer is positioned to receive blue light and convert it to green/yellow, while the second layer converts remaining blue light to red. This spatial arrangement ensures that the angular distribution of converted light is more uniform, stabilizing the color point across different viewing angles while maintaining high color rendering index.
3Duration of action of stationary object
If the organic matrix in the light-converting layer becomes colored due to operating temperature, then the light source can operate, but intensity becomes unstable and color point shifts over time
Solution Approach 1:
The patent changes the material parameters by replacing the organic matrix with an inorganic ceramic matrix having superior thermal stability. The ceramic material maintains its optical properties at elevated temperatures, preventing the coloration and degradation that occurs in organic matrices. This parameter change enables long operational duration while maintaining stable intensity and color point throughout the device lifetime.
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 achieves stable color point and high efficiency by scattering primary and secondary radiation uniformly, reducing energy losses and enhancing color rendering index, with a color point variation of less than 0.02 in the CIE 1976 color coordinate system.
Implementation Method 1
convert at least part of the primary radiation emitted by the LED into secondary radiation. This process is called light conversion
Implementation Method 2
the light-converting element comprises a ceramic light-converting material whose microstructure is selected to be such that the color point of the mixed light comprising primary and secondary radiation is substantially independent of the angle of viewing
Implementation Method 3
at least one first electroluminescent light-source for emitting first primary radiation having a maximum intensity at a first wavelength
Data Source
AI summary
An arrangement for emitting mixed light including a primary and secondary radiation with at least one first electroluminescent light-source for emitting first primary radiation, at least one second electroluminescent light-source for emitting second primary radiation, and a light-converting element for absorbing at least one of the primary radiations and re-emitting the secondary radiation. The light-converting element is arranged so that the entire proportion of primary radiation in the mixed light passes through the light-converting element. The light-converting element is a ceramic light-converting material whose microstructure is selected to be such that the color point of the mixed light of primary and second radiation is substantially independent of the angle of viewing.