Oxynitride Phosphor for Red Light Emission and Luminance Stability
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Solution Overview
Problem
Conventional phosphors used in lighting instruments and image displaying apparatuses suffer from luminance deterioration and inadequate color rendering properties, particularly when exposed to excitation sources, and lack sufficient red light emission for improved color rendering.
Innovation Solution
Development of chemically stabilized inorganic phosphors with specific compositions based on divalent alkaline earth elements, silicon, oxygen, and nitrogen, activated by photoactive metals, which emit orange or red light at higher luminance and are synthesized using stable starting materials, allowing for improved productivity and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional phosphors (silicate, phosphate, aluminate, sulfide) are used, then the phosphor can be excited by high energy sources, but the luminance deteriorates during long-term usage
Solution Approach 1:
The patent changes the chemical composition parameters of the phosphor from conventional silicate/phosphate/aluminate/sulfide structures to a specific oxynitride structure (Ba2-x-yLxMyN2-yO where L is alkaline earth element and M is rare earth element). This fundamental parameter change in chemical composition provides both high initial luminance and excellent luminance stability during long-term usage, resolving the contradiction between reliability and duration.
2Reliability
If sialon phosphor is used instead of conventional phosphors, then luminance deterioration is reduced, but the phosphor only emits yellow light and lacks red light emission for improved color rendering
Solution Approach 1:
The patent introduces different rare earth elements (M) at specific local positions within the oxynitride crystal structure to create localized emission characteristics. By selecting specific rare earth elements (Eu, Ce, Nd, Sm, Tb, Dy, Ho, Er, Tm, Yb) and controlling their concentration (0.01-5 mol%), the phosphor can be tuned to emit specific wavelengths including red light, while maintaining the overall structural stability that provides luminance reliability. This local quality modification enables versatile color rendering.
Solution Approach 2:
The patent creates a composite phosphor system combining alkaline earth elements (Ba, Sr, Ca, Mg) as host lattice formers with rare earth elements (Eu, Ce, Nd, Sm, Tb, Dy, Ho, Er, Tm, Yb) as activators, and incorporates both nitrogen and oxygen in specific ratios. This composite material approach allows simultaneous achievement of structural stability for luminance reliability and tunable optical properties for versatile color rendering including red light emission.
3Adaptability or versatility
If phosphors with improved color rendering properties are developed, then red light emission is enhanced, but the chemical stability and durability may be compromised
Solution Approach 1:
The patent employs an inert oxynitride crystal structure environment that protects the sensitive rare earth activator ions from chemical degradation. The dense crystal lattice with specific Ba/M/Si/O/N stoichiometry creates a chemically stable host that shields the rare earth elements responsible for color rendering, preventing their oxidation or other chemical reactions that would compromise both color stability and overall chemical durability.
Solution Approach 2:
The composite oxynitride structure combining alkaline earth host (Ba2-x-yLxMyN2-yO) with rare earth activators creates a synergistic material system where the alkaline earth oxynitride provides chemical stability and structural integrity, while the rare earth elements provide tunable color rendering properties including red light emission. The specific composition ratios ensure both chemical stability and desired optical performance.
4Productivity
If conventional production methods are used, then the phosphor can be produced, but the starting materials require air exclusion and productivity is limited
Solution Approach 1:
The patent employs commercially available, air-stable starting materials (carbonates, oxides, nitrides) that can be handled in air without special precautions. This eliminates the need for expensive and complex air-exclusion equipment and procedures, significantly simplifying the manufacturing process and improving productivity while maintaining phosphor quality.
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 new phosphors exhibit enhanced luminance and color rendering properties, providing a rich red component and improved durability, suitable for applications in white LEDs and image displaying apparatuses without luminance deterioration.
Implementation Method 1
the property to emit fluorescence at long wavelengths between 570 nm and 700 nm
Implementation Method 2
the phosphor is excited by an excitation source having high energy such as vacuum ultraviolet light, ultraviolet light, electron beam, blue light, or the like, such that the phosphor is caused to emit visible light
Data Source
AI summary
The present invention aims at providing a chemically stabilized inorganic phosphor, among oxynitride phosphors including alkaline earths, which oxynitride phosphor emits orange or red light at longer wavelengths at higher luminance than conventional sialon phosphors activated by rare earths. The present invention further aims at providing a light emitting instrument based on the phosphor, for a lighting instrument excellent in color rendering property and for an image displaying apparatus excellent in durability.The solving means resides in provision of a fundamental phosphor comprising:a composition on a pseudo-ternary phase diagram including AO (A is one kind or two or more kinds of element(s) selected from Mg, Ca, Sr, and Ba; and AO is oxide of A), Si3N4, and SiO2 as end members, respectively, and satisfying all of the following conditions:in a composition formula, pAO-qSi3N4-rSiO2(p+q+r=1),0.1≦p≦0.95 (1),0.05≦q≦0.9 (2), and0≦r≦0.5 (3), andat least a metallic element M (M is one kind or two or more kinds of element(s) selected from Mn, Ce, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb) dissolved, in a solid state, in the composition.