White Light Emitting Device Phosphor Mixture
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Solution Overview
Problem
White light emitting devices using silicate-based phosphors face limitations in thermal stability and color rendering due to low full-width half-maximum (FWHM) and color reproducibility, especially in high-temperature conditions and when used with blue LED chips.
Innovation Solution
A white light emitting device is developed using a mixture of phosphors, including nitrogen-containing compounds and specific oxynitride-based phosphors, which enhance thermal stability and color rendering by adjusting the FWHM and peak wavelengths of green, yellow, and red light emissions to achieve desired color coordinates and high color reproducibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If silicate-based phosphors are used to achieve narrow FWHM, then color saturation is improved, but thermal stability deteriorates
Solution Approach 1:
The patent uses a composite phosphor system combining silicate-based phosphor (for narrow FWHM and color saturation) with nitride-based phosphor (for thermal stability). This composite approach allows both requirements to be satisfied simultaneously by leveraging the complementary strengths of different phosphor materials.
Solution Approach 2:
The patent optimizes the ratio of silicate-based phosphor to nitride-based phosphor to achieve the desired balance between FWHM and thermal stability. By adjusting the composition parameters, the system achieves both narrow emission bandwidth and high temperature resistance.
2Reliability
If nitride-based phosphors are used to achieve high thermal stability, then reliability is improved, but color rendering deteriorates due to low FWHM
Solution Approach 1:
The patent combines nitride-based phosphor (providing thermal stability) with silicate-based phosphor (providing narrow FWHM and excellent color rendering). The composite system achieves both high thermal stability and superior color rendering properties that neither phosphor alone can provide.
Solution Approach 2:
The patent assigns different functional roles to different phosphor components: nitride-based phosphor handles thermal stability requirements while silicate-based phosphor handles color rendering requirements. This functional differentiation allows optimal performance in both aspects.
3Device complexity
If a single yellow phosphor is used to simplify the device structure, then manufacturing complexity is reduced, but color rendering deteriorates
Solution Approach 1:
The patent segments the yellow phosphor function into multiple components: silicate-based phosphor for narrow bandwidth yellow emission and nitride-based phosphor for thermal stability. This segmentation allows each component to specialize in one aspect, achieving superior overall color rendering while maintaining manageable device complexity.
Solution Approach 2:
The patent uses a composite phosphor mixture containing both silicate-based and nitride-based phosphors to achieve excellent color rendering. The composite approach provides broader and more accurate color coverage compared to single phosphor systems.
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 provides white light with excellent color reproducibility and high color rendering properties, exceeding 69% based on the NTSC standard, while maintaining thermal stability, suitable for applications in display and illumination apparatuses.
Implementation Method 1
a wavelength conversion phosphor material is used to convert a particular wavelength of light from various light sources into a desired wavelength of light
Implementation Method 2
a light emitting diode (LED), among various light sources, is able to be driven with low power consumption and has excellent light efficiency
Data Source
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AI summary
There is provided a white light emitting device including: a blue LED emitting blue light; a red phosphor excited by the blue light, emitting red light, and including a nitrogen(N)-containing compound; a yellow phosphor excited by the blue light and emitting yellow light; a first green phosphor excited by the blue light, emitting first green light having a first full width half maximum, and including a nitrogen(N)-containing compound; and a second green phosphor excited by the blue light and emitting second green light having a second full width half maximum larger than the first full width half maximum of the first green phosphor.