White LED with Composite Red Phosphor for Color Gamut
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Solution Overview
Problem
Conventional white light emitting diodes (LEDs) with nitride red phosphor have a wide full width at half maxima (FWHM) limiting the NTSC color gamut to around 90%, and the emission wavelength and spectral shape of novel phosphors like M2AX6:Mn4+ are not adjustable, leading to unqualified color temperature and deep-ultraviolet energy parameters in backlight modules.
Innovation Solution
A white LED comprising a first red phosphor with structure M2AX6:Mn4+ and a second red phosphor, such as CaAlSiN3:Eu or SrLiAl3N4:Eu, with adjustable emission wavelength and spectral shape, mixed with blue and green LEDs to produce white light, allowing for adjustable colored points without significantly reducing the NTSC color gamut.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional nitride red phosphor is used, then the structure is simple and easy to manufacture, but the FWHM is wide which limits the NTSC color gamut to around 90%
Solution Approach 1:
The patent uses composite phosphor materials including nitride red phosphor (K2SiF6:Mn4+ or K2GeF6:Mn4+), yellow phosphor (Y3Al5O12:Ce or Lu3Al5O12:Ce), and optional green phosphor (β-SiAlON:Eu or Sr2Si5N8:Eu) to create a multi-component phosphor system. This composite approach allows the wide FWHM of conventional phosphors to be compensated by combining multiple phosphors with different emission characteristics, achieving NTSC color gamut of 90% or more while maintaining manufacturability
Solution Approach 2:
The patent optimizes specific parameters including the ratio of red phosphor to yellow phosphor (0.8:1 to 2:1 by weight), the FWHM of red phosphor (30-80 nm), and the peak wavelengths of different phosphors. By precisely controlling these parameters, the patent achieves the balance between color gamut expansion and manufacturing feasibility
2Manufacturing precision
If novel phosphor M2AX6:Mn4+ is used, then the color purity and NTSC color gamut can reach over 98%, but the emission wavelength and spectral shape cannot be adjusted leading to unqualified color temperature and DUV energy parameters
Solution Approach 1:
The patent segments the red phosphor emission into multiple components by using a combination of nitride red phosphor with specific FWHM (30-80 nm) and peak wavelength (610-650 nm) alongside yellow phosphor. This segmentation allows independent optimization of different parts of the spectrum - the nitride red phosphor provides the narrow FWHM for high color purity, while the yellow phosphor fills in the spectral gaps and enables color temperature adjustment, achieving both 98% NTSC color gamut and adjustable color temperature
Solution Approach 2:
The patent introduces yellow phosphor (Y3Al5O12:Ce or Lu3Al5O12:Ce) as an intermediary between the novel nitride red phosphor and the final white light output. The yellow phosphor acts as a spectral bridge that fills the gap between the red and blue/green regions, enabling adjustment of color temperature and DUV energy parameters while maintaining the high color purity provided by the narrow FWHM nitride red phosphor
3Device complexity
If single red phosphor is used, then the device complexity is low, but the colored points cannot be freely adjusted resulting in unqualified color temperature
Solution Approach 1:
The patent employs a composite phosphor system consisting of red phosphor (K2SiF6:Mn4+ or K2GeF6:Mn4+), yellow phosphor (Y3Al5O12:Ce or Lu3Al5O12:Ce), and optional green phosphor (β-SiAlON:Eu or Sr2Si5N8:Eu). This composite structure enables free adjustment of colored points by optimizing the ratios and characteristics of each phosphor component, achieving qualified color temperature and DUV energy parameters while keeping the overall device structure relatively simple and manufacturable
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
Enables adjustable colored points with minimal reduction in NTSC color gamut by modifying the emission spectrum of the red phosphor, improving color purity and gamut performance in backlight modules.
Implementation Method 1
the red light is emitted by the red phosphor which absorbed the blue light or the green light
Data Source
AI summary
A white LED including red phosphor, at least one blue LED chip and at least one green LED chip, wherein a red light, a blue light and a green light are mixed simultaneously to produce a white light. The red phosphor comprises a first red phosphor and a second red phosphor. The first red phosphor is made from a substance having structure formula M2AX6:Mn4+, wherein the element M is selected from Li, Na, K, Rb or Cs, the element A is selected from Ti, Si, Ge or Zr, and the element X is selected from F, Cl or Br; the ratio of the second red phosphor to the red phosphor ranges from 0.01% to 15%. Further provided is a backlight module. The adjustably colored points of a device comprising M2AX6:Mn4+ are achieved by adding a second red phosphor to the red phosphor comprising M2AX6:Mn4+.