Nitride Fluorescent Material with Fluoride Protective Layer
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Solution Overview
Problem
The existing nitride fluorescent materials, such as SLAN phosphors, tend to deteriorate with oxygen, heat, and water, leading to a need for improved durability in light emitting devices.
Innovation Solution
A method of producing a nitride fluorescent material with a composition containing elements like Ca, Sr, Ba, Mg, Li, Na, K, Eu, Ce, Tb, Mn, Al, and N, involving a calcined product that is treated with a fluorine-containing substance at temperatures between 200°C and 500°C to form a protective fluorine layer, enhancing durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If SLAN phosphor is used to achieve narrow half bandwidth and red light emission, then color reproducibility is improved, but durability deteriorates due to deterioration with oxygen, heat, and water
Solution Approach 1:
A fluoride layer is introduced as an intermediary protective coating on the surface of the SLAN phosphor particles. This fluoride layer acts as a barrier between the phosphor core and the external environment (oxygen, water, heat), preventing direct contact and chemical reactions that would otherwise cause deterioration. The fluoride layer thus mediates the interaction between the phosphor and environmental factors, protecting the phosphor while maintaining its optical properties.
Solution Approach 2:
The invention creates a composite structure consisting of a SLAN phosphor core surrounded by a fluoride layer. This composite material combines the excellent optical properties of SLAN phosphor (narrow half bandwidth, red emission) with the protective characteristics of fluoride compounds (chemical stability, resistance to oxygen and water). The composite structure thus achieves both improved color reproducibility and enhanced durability.
2Illumination intensity
If calcination is performed at high temperature to form the phosphor structure, then fluorescence characteristics are improved, but durability worsens due to surface degradation and reactivity
Solution Approach 1:
The fluoride layer is formed on the phosphor surface through a preliminary heat treatment step performed after the main calcination process. This preliminary protective action prepares the surface for service conditions by creating a stable fluoride coating before the phosphor is subjected to environmental stress. The fluoride formation step thus acts in advance to prevent subsequent degradation.
Solution Approach 2:
The fluoride layer serves as an intermediary protective barrier between the calcined phosphor core and the external environment. It mediates the interaction by preventing direct contact between reactive phosphor surfaces and harmful environmental factors such as oxygen, water, and moisture, thereby protecting the phosphor structure while preserving its fluorescence characteristics.
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 resulting nitride fluorescent material exhibits improved durability and stability, maintaining chromaticity and light emission characteristics even under high temperature and humidity conditions.
Implementation Method 1
bringing the calcined product in contact with a fluorine-containing substance and heat-treating the calcined product at a temperature in a range of 200° C. or more and 500° C. or less
Data Source
AI summary
A method of producing a nitride fluorescent material is provided. The nitride fluorescent material undergoes less change in chromaticity under a high-temperature and high-humidity condition and are excellent in durability. The nitride fluorescent material has a composition containing: at least one element selected from the group consisting of Ca, Sr, Ba, and Mg; at least one element selected from the group consisting of Li, Na, and K; at least one element selected from the group consisting of Eu, Ce, Tb, and Mn; Al; and N. The method includes: preparing a calcined product having the composition, bringing the calcined product in contact with a fluorine-containing substance, and heat-treating the calcined product at a temperature of 200° C. or more and 500° C. or less. A light emitting device using the nitride fluorescent material is also provided.