Phosphor Plate Particle Control for LED Color Uniformity
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Solution Overview
Problem
Ceramic composite wavelength conversion members in LED illumination systems suffer from color unevenness and reduced emission efficiency due to temperature increases, with insufficient consideration for maximizing emission efficiency and addressing chromaticity variations.
Innovation Solution
A phosphor plate with a sintered body comprising (Y1-x-y, Gdx, Cey)3Al5O12 particles and Al2O3 particles, where x and y are within specific ranges, and the particles have controlled average diameters and concentrations, optimizing the Gd/Ce content ratio and thickness to enhance light flux, temperature stability, and chromaticity uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If ceramic composite wavelength conversion members are used to improve heat resistance, then temperature stability is improved, but color unevenness occurs and emission efficiency is reduced
Solution Approach 1:
The patent applies parameter changes by precisely controlling the particle diameter of YAG phosphor particles (4-6 μm), the ratio of Al2O3 to YAG particles (1:2 to 2:1), and the sintering temperature (1600-1800°C). These parameter optimizations resolve the contradiction by achieving both heat resistance through ceramic sintering and color uniformity through controlled particle size and distribution, eliminating the color unevenness that typically occurs in ceramic composite wavelength conversion members.
Solution Approach 2:
The patent uses composite materials by combining YAG phosphor particles with Al2O3 ceramic particles in a sintered body. This composite structure provides the heat resistance of ceramic materials while the specific particle size control (4-6 μm YAG particles) and composition ratio prevent color unevenness, resolving the contradiction between temperature stability and color uniformity.
2Loss of energy
If particle diameter of phosphor is reduced to improve emission efficiency, then light conversion efficiency is improved, but chromaticity variation increases
Solution Approach 1:
The patent applies parameter changes by optimizing the particle diameter of YAG phosphor particles to a specific range (4-6 μm). This parameter optimization resolves the contradiction by achieving high emission efficiency through adequate particle size while maintaining chromaticity uniformity, avoiding both the efficiency loss from oversized particles and the chromaticity variation from excessively small particles.
3Illumination intensity
If concentration of phosphor particles is increased to improve light flux, then light emission intensity is improved, but in-plane uniformity deteriorates
Solution Approach 1:
The patent applies parameter changes by optimizing the concentration ratio of Al2O3 to YAG particles (1:2 to 2:1) and controlling the absolute concentration of YAG particles (20-30 vol%). This resolves the contradiction by achieving high light flux through sufficient phosphor concentration while maintaining in-plane uniformity through the buffering effect of Al2O3 particles and optimized distribution, preventing color unevenness even at high phosphor concentrations.
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 phosphor plate achieves high light flux with minimal emission efficiency reduction at elevated temperatures and reduced chromaticity differences, providing improved in-plane uniformity and orientation characteristics.
Implementation Method 1
the mainstream method for obtaining white light is to mix light emitted from a blue LED and outgoing light from a phosphor that emits yellow light which is complementary color of blue in response to the blue light incident from the blue LED
Implementation Method 2
obtaining a second sintered body by performing secondary firing on the first sintered body by hot isostatic pressing (HIP)
Data Source
AI summary
The present invention relates to a phosphor plate including a sintered body including (Y1-x-y, Gdx, Cey)3Al5O12 particles and Al2O3 particles, in which 0.07≤x≤0.11 and 0.010≤y≤0.015 are satisfied, the (Y1-x-y, Gdx, Cey)3Al5O12 particles in the sintered body has an average particle diameter of 4 μm or more and 6 μm or less, the (Y1-x-y, Gdx, Cey)3Al5O12 particles has a concentration of 20 vol % or more and 30 vol % or less with respect to a total amount 100 vol % of the (Y1-x-y, Gdx, Cey)3Al5O12 particles and the Al2O3 particles, a ratio of an average particle diameter of the Al2O3 particles to the average particle diameter of the (Y1-x-y, Gdx, Cey)3Al5O12 particles is 1 or more and 2 or less, and the sintered body has a total thickness of 150 μm or more and 250 μm or less.