Luminescent Ceramic LED with Partial Conversion Layer
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Solution Overview
Problem
Existing illumination devices struggle to adjust their output spectrum simply and reproducibly to achieve a white output light with a color temperature lower than 5000 K and a high color rendering index, often using complex procedures and materials that are difficult to control, such as phosphor powders with binders that deteriorate at higher temperatures.
Innovation Solution
An illumination device comprising a light emitting diode (LED) with a first and second luminescent ceramic conversion layer, where the second layer covers only a fraction of the emission surface, allowing a portion of primary light to exit without passing through, and using materials like YAG:Ce and Ca-SiAlON:Eu to convert blue or UV light into longer wavelengths, enabling precise control over the color point and spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If phosphor powders with binders are used to adjust the output spectrum, then the color temperature and color rendering can be modified, but the binders deteriorate at higher temperatures and the composition control becomes complex and difficult to reproduce
Solution Approach 1:
The patent changes the material parameter from organic phosphor binders to inorganic luminescent ceramics, which maintain stable chemical composition and optical properties at high temperatures. The ceramic material composition can be precisely controlled during sintering to achieve desired emission spectra without thermal degradation.
Solution Approach 2:
The invention uses composite luminescent ceramic materials with specific compositions (e.g., YAG:Ce, LuAG:Ce) that combine multiple elements to achieve both high temperature stability and tunable optical properties. These composite ceramics provide reliable spectral adjustment without the deterioration issues of organic binders.
2Manufacturing precision
If multiple conversion layers are used to achieve desired color temperature and color rendering, then the spectral control is improved, but the device structure and manufacturing process become more complex
Solution Approach 1:
The patent divides the spectral conversion function into multiple discrete luminescent ceramic layers, each with specific emission characteristics. This segmentation allows independent optimization of each layer's composition and thickness to achieve precise overall spectral control while maintaining manufacturing simplicity through modular assembly.
Solution Approach 2:
The invention controls the spectral output by adjusting the geometric dimension (area fraction) of each conversion layer rather than relying solely on material composition ratios. By varying the area coverage of each luminescent ceramic layer, precise spectral control is achieved through simple geometric design rather than complex chemical mixing.
3Adaptability or versatility
If the second conversion layer covers the entire emission surface, then all primary light is converted, but no portion of the primary light can exit without conversion and spectral control flexibility is reduced
Solution Approach 1:
The patent applies different conversion properties to different local areas of the emission surface. The second conversion layer is applied only to specific regions (with area fraction between 0.01 and 0.5) rather than uniformly across the entire surface, allowing primary light in uncovered areas to exit without conversion while converted light provides the desired spectral components in covered areas.
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 design allows for a warm white light with a Correlated Color Temperature below 5000 K and high color rendering index, with precise control over the color point and efficiency, using luminescent ceramic converters that are stable at high temperatures and easy to handle, overcoming the limitations of traditional phosphor-based solutions.
Implementation Method 1
a first and second luminescent ceramic conversion layer for converting primary photons emitted by the active layer to different wavelengths
Data Source
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AI summary
The invention relates to an illumination device (10) that comprises an active layer (11), for example a blue LED, covered with a first luminescent ceramic converter layer (12) and partially covered with a second luminescent ceramic converter layer (13). The first and second conversion layers (12, 13) convert primary photons (?p) emitted by the active layer (11) into photons of different, longer wavelengths (?1, ?2), wherein the color point of the illumination device (10) can be adjusted by adjusting the relative size of the second conversion layer (13).