Reflective Wavelength-Converting Layer Spaced from LED Source
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional phosphor-converted light emitting devices face challenges in achieving color uniformity and efficiency due to variations in light path and heat-induced degradation of phosphor materials when phosphor is applied directly to the surface of LEDs.
Innovation Solution
A structure featuring a thick, reflective wavelength-converting layer spaced apart from the light source, with a transparent member and collimating optics, allowing for efficient cooling and precise control of the color point, and using deposition techniques like screen printing on a heat sink or optical plate for the wavelength-converting layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If phosphor is applied directly to the surface of LEDs, then the device structure is simplified and manufacturing is easier, but color uniformity deteriorates and heat-induced degradation occurs
Solution Approach 1:
The device is segmented into distinct functional zones: a light source region, a transparent member, and a wavelength-converting layer spaced apart from the light source. This segmentation allows the phosphor to be applied on a separate surface (optical plate or heat sink) rather than directly on the LED, enabling better control over phosphor distribution and light conversion while simplifying the manufacturing process.
2Device complexity
If phosphor is applied directly to the light source surface, then the device structure is simpler, but heat-induced efficiency loss increases
Solution Approach 1:
The wavelength-converting layer is extracted from the immediate vicinity of the light source and positioned on a separate surface (optical plate or heat sink) spaced apart from the LED. This extraction removes the phosphor from the high-heat zone, reducing thermal degradation and efficiency loss while maintaining a relatively simple overall device structure.
Solution Approach 2:
A transparent member (optical plate) or heat sink serves as an intermediary between the light source and the wavelength-converting layer. This intermediary allows the phosphor to be positioned away from the heat-generating LED while still receiving the necessary light for wavelength conversion, thereby reducing heat-induced efficiency loss without significantly increasing device complexity.
3Reliability
If phosphor layer is spaced apart from light source, then heat-induced degradation is reduced and color point control is improved, but device complexity increases
Solution Approach 1:
The surface where the wavelength-converting layer is applied serves multiple functions: it can be an optical plate that also acts as a light diffuser and structural component, or it can be the heat sink that provides both thermal management and a mounting surface for the phosphor. This multi-functionality reduces the need for additional components, thereby limiting the increase in device complexity while achieving improved phosphor degradation resistance and color point control.
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 configuration ensures easy control of the color point, reduces heat-induced efficiency loss, and provides a cost-effective and reliable method for producing uniform light by separating the wavelength-converting layer from the light source and using efficient cooling mechanisms.
Implementation Method 1
light having a first peak wavelength (the 'primary light') can be converted into light having one or more longer peak wavelengths (the 'secondary light') using a process known as luminescence/fluorescence. The fluorescent process involves absorbing the primary light by a wavelength-converting material such as a phosphor and exciting the luminescent centers of the phosphor material, which emit the secondary light.
Implementation Method 2
A counter reflecting surface is provided opposite to a light emitting element in its light emitting surface... The light emitting diode reflects externally incident light with a reflectivity greater than 40 percent
Data Source
Figure 1
Figure 2~3
Figure 4~6
AI summary
A light source (30) configured to emit first light is combined with a wavelength-converting layer (42). The wavelength-converting layer is disposed in a path of first light, is spaced apart from the light source, and includes at least one wavelength-converting material such as a phosphor configured to absorb first light and emit second light. The wavelength-converting layer is disposed between a reflective layer and the light source. In some embodiments, the wavelength-converting layer is a thick layer.