Fluoride Phosphor Repose Angle Control for LED Stability
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Solution Overview
Problem
White LEDs using K2SiF6:Mn4+ phosphor face issues with unstable brightness and low yield, requiring a fluoride phosphor with improved external quantum efficiency for stable light emission characteristics.
Innovation Solution
A fluoride phosphor with a specific composition A2M(1-n)F6:Mn4+n, where A is an alkali metal element like potassium and M is silicon or germanium, exhibiting a repose angle of 30° to 60°, bulk density of 0.80 to 1.40 g/cm3, and a span value of 1.5 or less, ensuring stable and efficient light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If K2SiF6:Mn4+ phosphor is used to improve color rendering and color reproducibility, then color quality is improved, but light emission characteristics become unstable and yield decreases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the Mn4+ doping concentration (0.01 to 0.1 mol ratio relative to K2SiF6) and optimizing sintering parameters (temperature 900-1100°C, atmosphere control) to achieve stable light emission characteristics. This resolves the contradiction by finding the optimal parameter range that ensures both color quality and emission stability
Solution Approach 2:
The patent uses composite material approach by combining K2SiF6 host lattice with Mn4+ activator ions to create a phosphor material that exhibits both sharp emission spectrum (for color quality) and enhanced stability (for reliable light emission). The composite structure of host-guest atoms provides both optical performance and manufacturing consistency
2Use of energy by moving object
If Eu2+ activated nitride or oxynitride phosphor is used to achieve high fluorescence conversion efficiency, then brightness is improved, but emission spectrum becomes broad and color reproduction range is reduced
Solution Approach 1:
The patent applies local quality principle by selecting Mn4+ as the activator ion which provides localized sharp emission lines at specific wavelengths (610-650 nm range) rather than broad emission. This localized emission characteristic enables precise color control while maintaining high conversion efficiency, resolving the contradiction between brightness and color reproduction range
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 fluoride phosphor achieves stable production of white LEDs with enhanced external quantum efficiency and improved light emission characteristics, reducing variations and maintaining brightness.
Implementation Method 1
a fluoride phosphor having a composition represented by the following general formula (1) and a repose angle of 30° or more and 60° or less... A2M(1-n)F6:Mn4+n... excited by blue light and emits red light
Data Source
AI summary
Provided is a fluoride phosphor that has a good external quantum efficiency and is suitable for stably producing white LEDs. The fluoride phosphor has a composition represented by a general formula (1) and a repose angle of 30° or more and 60° or less. general formula: A2M(1-n)F6:Mn4+n (1), wherein 0<n≤0.1, the element A is one or more alkali metal elements including at least K, and the element M is a simple substance of Si, a simple substance of Ge, or a combination of Si and one or more elements selected from the group consisting of Ge, Sn, Ti, Zr, and Hf.