Garnet Phosphor Ceramic Sheets for White LED Efficiency
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Solution Overview
Problem
Conventional white-LED systems using YAG phosphor powders in plastic encapsulants suffer from light scattering, leading to reduced luminance efficiency and stability issues, and require complex processing for red phosphor layers, while nitride or sulfide phosphors pose processing difficulties and stability concerns.
Innovation Solution
A lighting apparatus with a composite of garnet-based emissive layers, where both layers are doped with a common dopant and sintered together without resin or adhesive, enhancing absorption efficiency and transparency, and allowing for simpler processing of blue, green, and red phosphor layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If YAG phosphor powders are dispersed in plastic encapsulant resin, then the LED structure is simple to manufacture, but light scattering occurs leading to reduced luminance efficiency
Solution Approach 1:
The patent changes the physical state of the phosphor from powder to ceramic plate/film form, and changes the matrix material from plastic resin to translucent/transparent ceramic. This parameter change eliminates light scattering while maintaining manufacturing feasibility through sintering processes.
Solution Approach 2:
The patent uses composite ceramic materials combining phosphor particles within a ceramic matrix to create translucent or transparent phosphor ceramic plates. This composite structure allows light transmission while maintaining phosphor emission properties, resolving the contradiction between manufacturing simplicity and luminance efficiency.
2Ease of manufacture
If YAG phosphor powders are used in conventional white-LED, then the device is easy to manufacture, but heat stability and durability are poor
Solution Approach 1:
The patent changes the matrix material from organic plastic resin to inorganic translucent/transparent ceramic, which provides superior heat resistance and chemical stability. This parameter change maintains manufacturing feasibility while dramatically improving reliability and durability under thermal and UV conditions.
3Illumination intensity
If different dopants are used for yellow and red phosphor layers, then color rendering is improved, but processing complexity increases
Solution Approach 1:
The patent merges multiple phosphor functions into a single phosphor ceramic plate containing multiple phosphor particles with different dopants (Ce³⁺ for yellow, Eu³⁺ for red). This consolidation maintains excellent color rendering while simplifying processing by eliminating the need for separate phosphor layer fabrication and assembly steps.
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 improves luminance efficiency, reduces backscattering, and enhances stability and processing simplicity, achieving warm white light with high color rendering index and correlated color temperature, similar to incandescent bulbs.
Implementation Method 1
a first emissive layer comprising a first garnet phosphor and a second emissive layer comprising a second garnet phosphor... the light source configured to emit radiation having a wavelength of peak emission between about 360 nm and about 500 nm
Data Source
AI summary
Some embodiments disclosed herein include a lighting apparatus having a composite. The composite may include a first emissive layer and a second emissive layer. The first emissive layer may include a first garnet phosphor having a common dopant. The second emissive layer may include a second garnet phosphor having the common dopant. In some embodiments, the first emissive layer and the second emissive layer are fixed together. Some embodiments disclosed herein include efficient and economic methods of making the composite. The method may include, in some embodiments, sintering an assembly that includes pre-cursor materials for the first emissive layer and the second emissive layer.