Multiphase Phosphor for LED Stability
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Solution Overview
Problem
Current fluorescent materials used in LEDs do not satisfy the requirements for high luminous efficiency and light output stability needed for white light emission.
Innovation Solution
A multiphase phosphor compound comprising a sulfide crystallographic phase and an oxide crystallographic phase, specifically strontium thiogallate (SrGa2S4) and magnesium gallium oxide (MgGa2O4), doped with europium (Eu2+) to enhance light emission efficiency and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional phosphors (YAG:Ce) are used in white LEDs, then the device can be manufactured with existing technology, but the luminous efficiency and light output stability are insufficient
Solution Approach 1:
The patent employs a composite phosphor system combining YAG:Ce (yellow phosphor) with Sr2Si5N8:Eu2+ (green phosphor) and CaAlSiN3:Eu2+ (red phosphor). This composite approach enables simultaneous achievement of high luminous efficiency, broad spectral coverage, and stable light output by leveraging the complementary properties of each phosphor component while maintaining compatibility with existing LED manufacturing processes
2Illumination intensity
If phosphors with high excitation efficiency are sought to expand chromaticity zone, then the color rendering improves, but the light output stability and luminous efficiency deteriorate
Solution Approach 1:
The patent optimizes the excitation wavelength parameter by selecting a blue LED chip emitting at 450nm, which matches the peak excitation wavelengths of all three phosphors (YAG:Ce, Sr2Si5N8:Eu2+, and CaAlSiN3:Eu2+). This parameter alignment ensures high excitation efficiency across all phosphors simultaneously, expanding the chromaticity zone while maintaining stable light output and high luminous efficiency
3Ease of manufacture
If blue LED is combined with yellow phosphor to produce white light, then the manufacturing is simplified, but the luminous efficiency and brightness are limited
Solution Approach 1:
The patent extends the simple blue LED + yellow phosphor approach by incorporating three phosphors total: YAG:Ce (yellow), Sr2Si5N8:Eu2+ (green), and CaAlSiN3:Eu2+ (red). This composite phosphor system maintains manufacturing simplicity through co-firing or sequential firing processes while dramatically improving luminous efficiency by capturing a broader spectrum of blue LED emission and converting it to multiple color channels, thereby increasing overall light output and brightness
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 phosphor compound achieves high luminous efficiency and good light output stability by shifting the peak wavelength and increasing intensity, leading to improved brightness and product quality in white light emitting devices.
Implementation Method 1
a phosphor absorbing light emitted from the light source to emit light
Data Source
AI summary
There are provided phosphors having high luminous efficiency at desired wavelengths and good light output stability and a light emitting device using the same. A phosphor according to an aspect of the invention includes a sulfide crystallographic phase and an oxide crystallographic phase. Here, the phosphor is a multiphase compound in which the sulfide crystallographic phase and the oxide crystallographic phase exist together.