Packaged White Light Emitting Device with Layered Phosphor Structure
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Solution Overview
Problem
Manganese-activated fluoride photoluminescence materials are costly, require high usage amounts, and suffer from poor reliability and moisture sensitivity, making them impractical for widespread use in light emitting devices, especially in warm white applications.
Innovation Solution
A packaged white light emitting device design featuring a layered photoluminescence structure with a first layer comprising 75-100 wt% manganese-activated fluoride photoluminescence material and a second layer generating light in the green to red spectrum, positioned to optimize blue light absorption and protect against moisture, reducing the overall material usage and enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If manganese-activated fluoride phosphors are used to achieve high color gamut and CRI, then color quality is improved, but manufacturing cost increases significantly due to high material usage and material cost
Solution Approach 1:
The patent divides the phosphor system into two separate layers: a first layer containing manganese-activated fluoride phosphor for red emission, and a second layer containing green to red phosphors. This segmentation allows each layer to be optimized independently, reducing the total amount of expensive manganese-activated fluoride phosphor needed while maintaining color quality.
Solution Approach 2:
The patent transitions from a single-layer phosphor system to a multi-layer vertical structure. By stacking phosphor layers at different positions relative to the LED chip, the system achieves better light extraction and color mixing efficiency, reducing the quantity of phosphor material required.
2Illumination intensity
If high loading of photoluminescence material is used to achieve desired color point, then color quality is improved, but dispensing process stability deteriorates
Solution Approach 1:
The patent segments the high-concentration phosphor material into the first layer, while the second layer contains different phosphor materials at potentially lower concentrations. This segmentation allows the high loading required for color quality to be isolated to one layer, improving overall dispensing stability.
Solution Approach 2:
The patent applies different phosphor material compositions and concentrations to different layers. The first layer near the LED chip uses manganese-activated fluoride phosphor optimized for red emission, while the second layer uses green to red phosphors, creating local optimization that improves both color quality and manufacturability.
3Illumination intensity
If fluoride-based phosphor materials are used to achieve narrow red spectrum and high color gamut, then color quality is improved, but reliability deteriorates due to moisture sensitivity and corrosive byproducts
Solution Approach 1:
The patent introduces a wavelength converter layer as an intermediary between the LED chip and the manganese-activated fluoride phosphor. This layer converts blue light to green light, which then excites the red phosphor, reducing the phosphor's exposure to moisture and corrosive environments while maintaining color quality.
Solution Approach 2:
By stacking the manganese-activated fluoride phosphor in a separate first layer adjacent to the LED chip, the patent creates a protected configuration where the phosphor is shielded from environmental moisture, improving reliability while maintaining its narrow red spectrum emission for high color gamut.
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
Significantly reduces the amount of manganese-activated fluoride photoluminescence material required, lowers manufacturing costs, and improves moisture reliability and thermal stability, particularly in warm white light emitting devices.
Implementation Method 1
manganese-activated fluoride photoluminescence material (phosphor)... which absorb a portion of the excitation light (typically blue) emitted by the LED and re-emit light of a different color (wavelength)
Implementation Method 2
a first photoluminescence layer comprising from 75 wt % to 100 wt % a manganese-activated fluoride photoluminescence material... and a second photoluminescence layer comprising photoluminescence material for generating light with a peak emission wavelength in a range from 500 nm to 650 nm
Data Source
AI summary
A white light emitting package (20) comprises: a solid-state excitation source (LED 30) for generating excitation light with a dominant wavelength in a range 440 nm to 470 nm; and a layered photoluminescence structure. The layered photoluminescence structure comprises a first photoluminescence layer (32) comprising from 75 wt % to 100 wt % of a manganese-activated fluoride photoluminescence material of the total photoluminescence material content of the first photoluminescence layer, and a second photoluminescence layer (34) comprising photoluminescence material for generating light with a peak emission wavelength in a range from 500 nm to 650 nm. The second photoluminescence layer is disposed on the first photoluminescence layer and the first photoluminescence layer is in closer proximity to the solid-state excitation source than the second photoluminescence layer.