Wide Color Gamut LED Lighting Unit with Dual Red Phosphors
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Solution Overview
Problem
Current phosphor converted LED solutions suffer from limited intensity in the red spectral region, hindering the production of warm white devices and reducing luminous efficiency due to the limited spectral bandwidth of Eu(II)-activated phosphors, which restricts the achievable color gamut in LCD display backlighting.
Innovation Solution
A lighting unit comprising a combination of blue, green, and red luminescent materials, including a broad band red emitter and a narrow band red emitter, such as (Ba,Sr,Ca,Mg)AlSiN3:Eu and Mn-activated fluoride phosphors, excited by a blue LED, to achieve a wider color gamut by enhancing spectral efficiency and color separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If Eu(II)-activated phosphors are used for red emission, then the device structure is simple, but the spectral bandwidth is limited and color gamut is restricted
Solution Approach 1:
The patent combines multiple phosphor materials with different emission characteristics: Eu(II)-activated phosphors for broad band red emission, Mn(IV)-activated fluorides for narrow band red emission, and green phosphors. This composite phosphor system achieves a wide color gamut (NTSC 80% or higher) while maintaining a relatively simple LED-based device structure.
2Manufacturing precision
If narrow band red phosphors are used, then color gamut is improved, but intensity in the red spectral region is reduced
Solution Approach 1:
The patent merges two types of red-emitting phosphors with complementary spectral characteristics: broad band Eu(II)-activated phosphors that provide high intensity in the red region, and narrow band Mn(IV)-activated fluorides that extend the color gamut. The combination achieves both high red intensity and wide color gamut (NTSC 80% or higher).
3Illumination intensity
If broad band red phosphors are used, then red spectral intensity is high, but spectral efficiency is limited
Solution Approach 1:
The patent employs a composite phosphor system where Mn(IV)-activated narrow band fluorides provide high spectral efficiency with concentrated emission, while Eu(II)-activated broad band phosphors supplement the red intensity. The combination achieves both high spectral efficiency and adequate red intensity, enabling NTSC 80% or higher color gamut.
4Manufacturing precision
If multiple phosphor types are combined, then color gamut is widened, but device complexity increases
Solution Approach 1:
The patent creates a composite phosphor layer combining Eu(II)-activated phosphors, Mn(IV)-activated fluorides, and green phosphors. This composite approach achieves NTSC 80% or higher color gamut while maintaining a unified layer structure that can be applied as a single phosphor coating on the LED chip, balancing color performance with manufacturing simplicity.
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 combination of phosphors achieves a National Television System Committee (NTSC) color gamut of 80% or higher, significantly improving color reproduction and luminous efficiency in LCD display devices by providing a wider range of colors.
Implementation Method 1
a source of green light, a first source of red light comprising a first red luminescent material... and a second source of red light comprising a second red luminescent material... excited both with a blue LED
Implementation Method 2
source of blue light... source of green light... first source of red light... second source of red light
Data Source
Figure 1a~1c
Figure 1d~1e
Figure 2a~2b
AI summary
The invention provides a lighting unit comprising a source of blue light, a source of green light, a first source of red light comprising a first red luminescent material, configured to provide red light with a broad band spectral light distribution, and a second source of red light comprising a second red luminescent material, configured to provide red light with a spectral light distribution comprising one or more red emission lines. Especially, the first red luminescent material comprises (Mg,Ca,Sr)AlSiN3:Eu and/or (Ba,Sr,Ca)2Si5- xAlxOxN8-x:Eu, and the second red luminescent material comprises K2SiF6:Mn.