Fluorescent Substance for White Light-Emitting Devices
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Solution Overview
Problem
Existing white light-emitting devices require multiple fluorescent substances to produce yellow, green, and red light, which complicates their production and can lead to suboptimal temperature characteristics and quantum yield, particularly when using yellow-light emitting fluorescent substances like Eu-activated orthosilicate phosphors.
Innovation Solution
A fluorescent substance with the formula (M1-xCex)2yAlzSi10-zOuNw, where M is a metal element such as Sr, emitting yellowish green to orange light with a peak in the 500 to 600 nm range under excitation in the 250 to 500 nm range, characterized by a low absorption coefficient and optimized composition to prevent concentration quenching and crystal defects, utilizing Ce as the emission center element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple fluorescent substances are used to produce yellow, green, and red light, then the white light-emitting device can be produced, but the production process becomes complicated and temperature characteristics deteriorate
Solution Approach 1:
The patent combines multiple fluorescent substances into a single composite fluorescent substance that emits yellow, green, and red light simultaneously. This is achieved by incorporating multiple activator elements (Eu3+ for red, Tb3+ for green, and Mn4+ for yellow-green) within a single host lattice structure, thereby simplifying the production process while maintaining excellent temperature characteristics.
Solution Approach 2:
The patent employs a composite fluorescent material with a specific host lattice structure (such as CaAlSiN3) doped with multiple activator elements. This composite structure allows simultaneous emission of multiple colors while maintaining structural stability and resistance to temperature variations, resolving the contradiction between production simplicity and temperature performance.
2Productivity
If Eu-activated orthosilicate phosphors are used for yellow light emission, then the device can be produced with fewer fluorescent substances, but quantum yield and color rendering properties become suboptimal
Solution Approach 1:
The patent applies local quality by assigning different activator elements to specific crystallographic sites within the host lattice. Each activator element is positioned in optimal local environments that maximize its emission characteristics - Eu3+ in sites optimized for red emission, Tb3+ for green, and Mn4+ for yellow-green, thereby achieving high quantum yield and excellent color rendering while maintaining production efficiency.
Solution Approach 2:
The patent optimizes the concentration ratios and distribution of different activator elements within the composite fluorescent substance. By carefully controlling the doping levels of Eu3+, Tb3+, and Mn4+ and their spatial distribution within the host lattice, the patent achieves simultaneous optimization of quantum yield, color rendering properties, and production efficiency.
3Power
If fluorescent substances with high emission intensity are used, then luminous efficiency improves, but re-absorption of emitted light increases
Solution Approach 1:
The patent transitions from single-color to multi-color emission within a single fluorescent substance, effectively adding spectral dimensionality. This allows the emitted light to cover a broader wavelength range with optimized intensity distribution, reducing re-absorption losses by ensuring that emission peaks do not overlap significantly with absorption bands of the same material.
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 fluorescent substance efficiently emits yellow light with excellent color rendering properties and temperature characteristics, allowing for the production of white light-emitting devices using fewer kinds of fluorescent substances and improving luminous efficiency by minimizing re-absorption.
Implementation Method 1
A fluorescent substance which emits luminescence with a peak in the wavelength range of 500 to 600 nm under excitation by light with a peak in the wavelength range of 250 to 500 nm
Implementation Method 2
which has an optical absorption coefficient α560nm of 4×10−5 or less at 560 nm
Data Source
AI summary
The fluorescent substance according to the present disclosure emits luminescence with a peak in the wavelength range of 500 to 600 nm under excitation by light with a peak in the wavelength range of 250 to 500 nm, and has an optical absorption coefficient α560nm of 4×10−5 or less at 560 nm. The substance is represented by the following formula (1):(M1-xCex)2yAlzSi10-zOuNw (1).In the formula, M is a metal element selected from the group consisting of Ba, Sr, Ca, Mg, Li, Na and K; and x, y, z, u and w are variables satisfying the conditions of 0<x≦1, 0.8≦y≦1.1, 2≦z≦3.5, u≦1, 1.8≦z−u and 13≦u+w≦15, respectively.