Mn4+ Activated Complex Fluoride Phosphors for High LER LED Backlights
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Solution Overview
Problem
Current LED backlights using yellow phosphors have excessive yellow emission, which reduces the color gamut and luminous efficacy, making it difficult to achieve high CRI and LER values simultaneously at high CCTs, particularly for applications requiring lower CCTs and higher CRIs.
Innovation Solution
The use of red line-emitting phosphors, such as complex fluoride phosphors activated with Mn4+, in conjunction with green and blue phosphors, to produce white light with improved LER and CRI values, minimizing yellow emission and enhancing color gamut, especially when used with UV or visible LED chips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If yellow phosphors are used in LED backlights to achieve high CCT values, then the CCT can be greater than 5000K, but the color gamut is strongly reduced due to excessive yellow emission
Solution Approach 1:
The patent changes the emission wavelength parameter of the red phosphor from conventional deep red (>650nm) to a specific range of 600-650nm. This parameter change allows the red phosphor to fill the spectral gap without adding excessive yellow emission, thereby maintaining high color gamut while achieving the required CCT values above 5000K
Solution Approach 2:
The patent uses a composite phosphor system combining red line-emitting phosphors (600-650nm), green phosphors, and blue phosphors. This composite material approach replaces the conventional yellow phosphor system, enabling simultaneous achievement of high CCT, high color gamut, and high LER values
2Temperature
If yellow phosphors are used to produce white light with high CCT, then the white light can be achieved, but the luminous efficacy is strongly reduced
Solution Approach 1:
The patent optimizes the emission wavelength parameter of the red phosphor to 600-650nm, which aligns better with the human eye's sensitivity curve (photopic luminosity function). This parameter optimization reduces energy loss in spectral regions where the eye is less sensitive, thereby improving luminous efficacy while maintaining high CCT
Solution Approach 2:
The patent changes the color distribution of the emitted light by using red line-emitting phosphors instead of yellow phosphors. This color change shifts the spectral power distribution toward regions of higher luminous efficiency, improving overall luminous efficacy at high CCT values
3Reliability
If red phosphors with emission maxima greater than 650 nm are used, then the CRI can be improved, but the LER is considerably impacted due to emission in the deep red region where eye sensitivity is low
Solution Approach 1:
The patent optimizes the emission wavelength parameter of the red phosphor to the 600-650nm range, which represents an optimal compromise between CRI and LER. This wavelength range maintains good color rendering for red objects while aligning with the peak sensitivity region of the human eye, thereby achieving both high CRI and high LER simultaneously
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
This approach allows for LED backlights to achieve high LER values of 280 lm/Wopt or greater at CCTs greater than 5000K with improved color gamut and CRI, while reducing yellow emission, thereby meeting the requirements for high-quality backlighting applications.
Implementation Method 1
A phosphor is a luminescent material that absorbs radiation energy in a portion of the electromagnetic spectrum and emits energy in another portion of the electromagnetic spectrum
Implementation Method 2
a green emitting phosphor having a peak emission wavelength between 510 and 550 nm; and either a) a blue LED chip having a peak emission wavelength between 440 and 480 nm
Data Source
AI summary
New phosphor materials including a complex fluoride phosphor activated with Mn4+ which may include at least one of (A) A2[MF7]:Mn4+, wherein A=Li, Na, K, Rb, Cs, NH4, or a combination thereof, and M=Nb, Ta or a combination thereof; and (B) A3[XF6]:Mn4+, wherein A=Li, Na, K, Rb, Cs, NH4, or a combination thereof, and X=Sc, Y, La, a lanthanide, Bi, or a combination thereof.