LED Light Conversion Layer for Stable Color Temperature
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Solution Overview
Problem
The variability in peak wavelengths of blue light emitted by LED semiconductor dies during manufacturing leads to inconsistent color temperatures in white LEDs due to inefficiencies in the phosphor conversion process, resulting in differing color temperatures among mass-produced LEDs.
Innovation Solution
A light source design where a significant portion of primary blue light is either directly emitted or efficiently converted into secondary yellow light, with a high conversion factor greater than 0.9, using a structured conversion layer with varying phosphor concentrations and patterns to minimize wavelength-dependent variations, and incorporating dichromatic or absorption coatings to stabilize the color temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a phosphor conversion layer is used to convert blue light to yellow light, then white light is generated, but the color temperature varies due to wavelength-dependent conversion efficiency
Solution Approach 1:
The conversion layer is divided into multiple regions with different phosphor concentrations. The first region has a higher phosphor concentration to efficiently convert blue light to yellow light, while the second region has a lower phosphor concentration to allow some blue light to pass through. This segmentation allows the device to generate white light with stable color temperature by balancing converted and unconverted blue light components.
Solution Approach 2:
Different regions of the conversion layer are assigned different phosphor concentrations tailored to their specific functions. The first region (higher concentration) is optimized for light conversion, while the second region (lower concentration) is optimized for wavelength transmission. This local quality differentiation resolves the contradiction by allowing each region to perform its function optimally, resulting in overall color temperature stability.
2Loss of energy
If the phosphor concentration is increased to improve conversion efficiency, then more yellow light is generated, but color temperature stability decreases due to wavelength sensitivity
Solution Approach 1:
The conversion layer is divided into multiple regions with different phosphor concentrations. The first region has a higher phosphor concentration to efficiently convert blue light to yellow light, while the second region has a lower phosphor concentration to allow some blue light to pass through. This segmentation allows the device to generate white light with stable color temperature by balancing converted and unconverted blue light components.
Solution Approach 2:
The phosphor concentration parameter is varied spatially across the conversion layer. By changing the concentration from high in the first region to low in the second region, the device optimizes both conversion efficiency and color temperature stability. This parameter change allows the system to achieve high overall conversion efficiency while maintaining color consistency despite wavelength variations.
3Loss of energy
If the conversion layer covers the entire light-emitting surface, then light conversion is maximized, but control over color temperature becomes difficult
Solution Approach 1:
The conversion layer is divided into multiple regions with different phosphor concentrations. The first region has a higher phosphor concentration to efficiently convert blue light to yellow light, while the second region has a lower phosphor concentration to allow some blue light to pass through. This segmentation allows the device to generate white light with stable color temperature by balancing converted and unconverted blue light components.
Solution Approach 2:
Instead of complete conversion across the entire surface, the invention uses partial conversion by creating a second region with lower phosphor concentration that allows some blue light to pass through unconverted. This partial action approach provides better control over color temperature while maintaining high overall conversion efficiency in the first region.
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 ensures a stable color temperature for white LEDs by minimizing the impact of peak wavelength variations and enhancing light conversion efficiency, producing consistent color temperatures across different LEDs.
Implementation Method 1
a phosphor portion as conversion element, which is arranged above the LED emitting surface, in order to convert the pump light into yellow light by active phosphor light absorption
Implementation Method 2
incorporating dichromatic or absorption coatings to stabilize the color temperature
Implementation Method 3
incorporating dichromatic or absorption coatings to stabilize the color temperature
Data Source
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AI summary
The invention relates to a light source to emit a mixture of primary and secondary light comprising an electroluminescent device like a light emitting diode LED or a laser, to emit the primary light into a light conversion element (3) to convert the primary light into the secondary light, where a first part of the primary light is emitted along a light path with a first conversion factor (11) for the primary light, and a second part of the primary light is emitted along a light path with a second conversion factor (12) for the primary light larger than the first conversion factor.