LED White Light Device with Multi-Layer Phosphor for High Color Rendering
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Solution Overview
Problem
Existing white light emitting devices using LEDs struggle to achieve high color rendering properties, particularly a high average color rendering index (Ra), which is essential for replicating natural light.
Innovation Solution
A white light emitting device configuration that includes a blue LED as the excitation light source, combined with specific phosphors such as a green, yellow, and red phosphor, where the peak wavelengths of these phosphors are strategically aligned to satisfy the condition 30≦λ1−λ0≦70, ensuring optimal color rendering by converting blue light into red, yellow, and green light within specific ranges, thereby achieving a neutral white color with a high Ra.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a blue LED with yellow phosphor is used for white light emission, then the device structure is simple, but the color rendering property (Ra) is insufficient
Solution Approach 1:
The patent divides the single phosphor layer into multiple phosphor layers with different characteristics. Specifically, it uses a first phosphor layer (yellow phosphor) and a second phosphor layer (red phosphor) with different peak wavelengths and half-value widths, allowing each layer to contribute differently to the overall emission spectrum, thereby improving color rendering while maintaining practical manufacturability
Solution Approach 2:
The patent employs composite phosphor materials with specific properties: the first phosphor layer uses yellow phosphor with peak wavelength 560-580nm and half-value width 80-100nm, while the second phosphor layer uses red phosphor with peak wavelength 610-650nm and half-value width 50-80nm. This composite structure enables superior color rendering (Ra≥95) by combining the emission characteristics of different phosphor materials
2Manufacturing precision
If multiple phosphors are added to improve color rendering, then the color rendering property (Ra) improves, but the device complexity increases
Solution Approach 1:
The patent assigns different local qualities to different phosphor layers: the first phosphor layer (yellow) provides broad spectrum coverage for general white light emission, while the second phosphor layer (red) specifically enhances the red region to improve color rendering. Each layer has optimized peak wavelengths and half-value widths tailored to its specific function in the overall color rendering system
Solution Approach 2:
The patent systematically varies key parameters of the phosphor materials: peak wavelengths (560-580nm for yellow, 610-650nm for red), half-value widths (80-100nm for yellow, 50-80nm for red), and thickness ratios (first layer 5-15μm, second layer 3-10μm). These parameter optimizations enable high color rendering while controlling device complexity through precise material selection
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 described configuration achieves an excellent color rendering property with an average color rendering index of 95 or more, ensuring a reliable and efficient light emitting device with minimal ultraviolet component, thus preventing constituent part deterioration.
Implementation Method 1
a first phosphor layer having a peak wavelength of 560 nm or more and 580 nm or less and a half-value width of 80 nm or more and 100 nm or less, a second phosphor layer having a peak wavelength of 610 nm or more and 650 nm or less and a half-value width of 50 nm or more and 80 nm or less
Data Source
AI summary
A light emitting device according to embodiments includes a light emitting element emitting light having a peak wavelength of 425 nm or more and 465 nm or less, a first phosphor emitting light having a peak wavelength of 485 nm or more and 530 nm or less, a second phosphor emitting light having a peak wavelength longer than that of the first phosphor, and a third phosphor emitting light having a peak wavelength longer than that of the second phosphor. Then, when the peak wavelength of the light emitting element is λ0 (nm) and the peak wavelength of the first phosphor is λ1 (nm), a relation of 30≦λ1−λ0≦70 is satisfied.