SiAlON Phosphor Aspect Ratio Control for Dispersion and Brightness
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Solution Overview
Problem
Current light emitting apparatus using trivalent cerium-activated phosphors face challenges with high temperature characteristics and uniform dispersion of phosphor particles, leading to reduced brightness and color gamut, particularly with β-type SiAlON phosphors having a columnar crystal structure.
Innovation Solution
A phosphor particle group of divalent europium-activated oxynitride green light emitting phosphors with a controlled crystal shape, where 60% or more of the particles have an aspect ratio between 1.0 and 3.0, and a median diameter of 6-20 μm, is used in conjunction with a gallium nitride-based semiconductor light emitting element to enhance brightness and color gamut.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If divalent europium-activated oxynitride green light emitting phosphor with columnar crystal structure is used, then color gamut and temperature characteristic are improved, but particle aggregation occurs during resin dispersion
Solution Approach 1:
The patent changes the aspect ratio parameter of phosphor particles from exceeding 5 to 3.0 or less, transforming the particle morphology from highly columnar to more equiaxed shapes. This parameter modification eliminates aggregation during resin dispersion while preserving the phosphor's excellent color gamut and temperature characteristics
Solution Approach 2:
The patent creates a composite phosphor particle system combining controlled aspect ratio morphology with divalent europium activation in oxynitride green light emitting material. This composite structure achieves both good dispersibility in resin and high color gamut performance
2Stability of the object's composition
If aspect ratio of phosphor particles is controlled to 3.0 or less, then uniform dispersion in resin is achieved, but luminous efficiency may be reduced
Solution Approach 1:
The patent optimizes the aspect ratio parameter to a specific range (greater than 1.0 and 3.0 or less), finding the optimal balance point where particles are sufficiently equiaxed for good dispersion yet retain enough anisotropy to maintain high luminous efficiency through controlled light emission properties
3Illumination intensity
If input energy is increased to achieve higher brightness, then luminous output is improved, but heat dissipation becomes more difficult
Solution Approach 1:
The patent converts the potential harm of high operating temperatures into a benefit by selecting phosphor particles with aspect ratio 3.0 or less that exhibit superior temperature characteristics. The controlled particle morphology ensures stable luminescence performance even at elevated temperatures, allowing high brightness operation without thermal degradation
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 solution enables a light emitting apparatus with improved brightness, color gamut, and temperature characteristics by ensuring efficient absorption of primary light and uniform dispersion of phosphor particles, resulting in a high-efficiency white light emission.
Implementation Method 1
a light emitting element of a gallium nitride-based semiconductor emitting primary light of 430-480 nm
Implementation Method 2
a light converter which absorbs a part of the primary light to emit secondary light having a longer wavelength than that of the primary light
Data Source
AI summary
Provided is a phosphor particle group of divalent europium-activated oxynitride green light emitting phosphor particles each of which is a β-type SiAlON substantially represented by a general formula: EuaSibAlcOdNe, where 0.005≦a≦0.4, b+c=12, d+e=16, wherein 60% or more of the phosphor particle group is composed of the phosphor particles in which a value obtained by dividing a longer particle diameter by a shorter particle diameter is greater than 1.0 and not greater than 3.0. A high-efficiency and stable light emitting apparatus using a β-type SiAlON, which includes a light converter using the phosphor particle group, and a phosphor particle group therefor are also provided.