LED Lighting Device Phosphor Self-Absorption Reduction
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Solution Overview
Problem
Self-absorption in lighting devices reduces luminance output due to overlapping phosphor excitation and emission spectra, limiting the efficiency of white light production in applications like LCD backlights and automotive lighting.
Innovation Solution
A novel geometry of wavelength converting members with a selective reflector is employed, where first and second wavelength converting members with different peak emissions are isolated from each other's irradiation, using a selective reflector to prevent self-absorption by reflecting the second electromagnetic radiation away from the first wavelength converting member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If phosphor layers are arranged in vertical geometry with red phosphor nearer to exiting element, then warm white light (CCT 2500-3500K) is achieved, but self-absorption occurs reducing total luminance output
Solution Approach 1:
The device segments the phosphor layers into multiple layers with different wavelength converting members (first, second, third phosphor layers) arranged in a specific vertical sequence. Each layer converts a portion of the blue light to different wavelengths, with the red phosphor layer positioned nearest to the exiting element to achieve warm white light while minimizing self-absorption effects through this segmented arrangement.
Solution Approach 2:
The patent applies local quality by positioning different phosphor layers at specific locations within the device. The red phosphor layer is placed nearest to the exiting element where it can effectively convert blue light to red wavelengths without significant self-absorption, while green and blue phosphor layers are positioned in intermediate and distant locations respectively, optimizing each layer's local contribution to the overall warm white light output.
2Temperature
If phosphor down converting process is used to produce white light, then CRI and warm white light are improved, but overlapping of phosphor excitation and emitting spectra reduces total luminance output
Solution Approach 1:
The device segments the wavelength conversion function across multiple phosphor layers instead of using a single phosphor material. This segmentation allows each layer to handle specific wavelength conversions independently, reducing the overlapping between excitation and emission spectra that causes self-absorption, while still achieving the desired warm white light with improved CRI.
Solution Approach 2:
The patent transitions from a single-layer phosphor approach to a multi-layer vertical structure, adding the dimensional aspect of layering. This vertical arrangement in multiple dimensions allows light to pass through layers sequentially, with each layer contributing to wavelength conversion without the harmful self-absorption effects that occur in single-layer configurations.
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 configuration significantly increases total output luminance by minimizing self-absorption, enhancing the efficiency of light production and maintaining warm white light characteristics.
Implementation Method 1
The first wavelength converting member absorbs at least a portion of the electromagnetic radiation originated from said radiation source
Implementation Method 2
emits a first electromagnetic radiation with peak wavelength λe1
Implementation Method 3
The second wavelength converting member absorbs at least a portion of the electromagnetic radiation originated from said radiation source
Implementation Method 4
emits a second electromagnetic radiation with peak wavelength λe2
Implementation Method 5
a selective reflector is included in the device and used to selectively reflect at least a portion of the second electromagnetic radiation with peak wavelength λe2 away from said first wavelength converting member
Data Source
AI summary
Provided are a lighting device, a backlighting device, and a display device that comprise a radiation source such as LED and wavelength converting members comprising phosphors. In one embodiment, self-absorption within the devices is suppressed or reduced by placing a selective reflector between two wavelength converting members, and the wavelength converting member emitting light with longer peak wavelength is substantially isolated from the irradiation of another wavelength converting member emitting light with shorter peak wavelength. In other embodiments, the wavelength converting members are arranged in strip configuration; or in adjacent hexagons configuration.