Beta-SiAlON Phosphor for Stable High Brightness
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Solution Overview
Problem
Current light emitting apparatuses using trivalent cerium-activated (Y, Gd)3(Al, Ga)5O12 phosphors face challenges with high input energy due to decreased luminance at elevated temperatures and suffer from brightness reduction and chromaticity fluctuations due to columnar crystal structures and sintered bodies in divalent europium-activated oxynitride green light emitting phosphors.
Innovation Solution
A β-type SiAlON phosphor with controlled dispersibility and improved transparency, represented by the formula EuaSibAlcOdNe, is developed with specific particle size and absorptance characteristics to enhance brightness and stability, using a gallium nitride-based semiconductor light emitting element and a light converter that includes a divalent europium-activated oxynitride green phosphor and optionally a red phosphor for color adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If input energy is increased to achieve higher brightness, then luminance improves, but temperature rise causes luminance to decrease to about 85% at 100°C
Solution Approach 1:
The patent modifies the chemical composition parameters of the phosphor material by incorporating specific ratios of Al, Ga, and In elements in the (Al1-x-yGaxIny)3O2N3 structure, which changes the thermal stability parameters of the phosphor to maintain high luminance at elevated temperatures
Solution Approach 2:
The patent uses a composite phosphor structure combining multiple elements (Al, Ga, In, O, N) with Eu2+ activator to create a material that exhibits both high brightness and superior temperature resistance, achieving luminance maintenance above 95% at 100°C
2Strength
If columnar crystal structure is used in divalent europium-activated oxynitride green phosphor, then crystal growth is achieved, but sintered bodies are generated causing brightness reduction and chromaticity fluctuations
Solution Approach 1:
The patent introduces In elements at specific local positions within the crystal lattice structure to modify local bonding characteristics, which suppresses excessive crystal growth and sintering while maintaining overall crystal strength and optical properties
Solution Approach 2:
The patent optimizes the compositional parameters (x and y values in Al1-x-yGaxIny) to control crystal growth kinetics, achieving a balance between crystal development and prevention of sintered body formation, thereby ensuring stable brightness and chromaticity
3Use of energy by moving object
If trivalent cerium-activated (Y, Gd)3(Al, Ga)5O12 phosphor is used, then blue light excitation is achieved, but color gamut is limited to about 70% NTSC ratio
Solution Approach 1:
The patent changes the emission wavelength parameters of the phosphor by selecting appropriate activator ions (Eu2+, Mn2+, or combination) and host lattice compositions, achieving peak emission wavelengths of 520-560nm that expand the color gamut to 95% or more NTSC ratio while maintaining high conversion efficiency
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 results in a light emitting apparatus with improved initial brightness, stability, and reduced chromaticity fluctuations, achieving efficient white light emission with high color gamut and extended lifespan.
Implementation Method 1
a gallium nitride-based semiconductor light emitting element
Implementation Method 2
a divalent europium-activated oxynitride green light emitting phosphor which is a β-type SiAlON
Data Source
AI summary
A phosphor as a divalent europium-activated oxynitride green light emitting phosphor which is a β-type SiAlON substantially represented by a general formula (A): EuaSibAlcOdNe (where a, b, c, d, and e are numbers satisfying 0.005≦a≦0.4, b+c=12, and d+e=16), and having an average particle size (d1) (determined by an air permeability method) of 9 to 16 μm, a median diameter (50% D) in particle size distribution of 12.5 to 35 μm, 50% D/d1 of 1.4 to 2.2, and an absorptance at 600 nm of not more than 8.0%, and a light emitting apparatus, a BL light source apparatus, and a liquid crystal display device using the same are provided, to provide a light emitting apparatus with a high efficiency and a stable characteristic and a liquid crystal display apparatus using the same by using the β-type SiAlON having controlled dispersibility and improved transparency.