Red Phosphor Composition for Narrow-Spectrum LED Light Conversion
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Solution Overview
Problem
Current red phosphors used in light-emitting devices have unclear emission intensity and broad spectral half peak widths, leading to inefficient conversion efficiency and color rendering issues in LED-based illumination and display applications.
Innovation Solution
A light-emitting device utilizing a phosphor with a specific crystal phase composition, characterized by a minimum reflectance of 20% or more in a prescribed wavelength region from the emission peak to 800 nm, incorporating elements such as Sr, Ca, Li, Al, and Eu, which enhances emission intensity and conversion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional red phosphors (KSF, S/CASN) are used, then the light-emitting device can be manufactured, but the emission intensity is insufficient and the full width at half maximum is broad (80-90 nm)
Solution Approach 1:
The patent changes the chemical composition parameters of the phosphor by incorporating specific ratios of Sr, Ca, Li, Al, and Eu elements to achieve both high emission intensity and narrow spectral width. The precise control of compositional parameters (molar ratios) enables simultaneous optimization of emission characteristics.
Solution Approach 2:
The invention uses a composite phosphor material combining multiple elements (Sr, Ca, Li, Al, Eu) in specific proportions to achieve superior optical properties that cannot be obtained with single-element phosphors. The composite structure allows synergistic effects that improve both emission intensity and spectral purity.
2Reliability
If KSF phosphor is used, then the light-emitting device can operate, but it is harmful to humans and the environment due to Mn-activation
Solution Approach 1:
The patent removes the harmful Mn-activator from the phosphor composition and replaces it with Eu (europium) as the activator element. This extraction of the harmful substance while maintaining or improving the emission intensity through alternative activator selection resolves the contradiction between safety and performance.
3Productivity
If phosphor with broad FWHM (80-90 nm) is used, then the light-emitting device can be manufactured, but the conversion efficiency is reduced due to inclusion of low relative luminous efficiency wavelength ranges
Solution Approach 1:
The patent optimizes the phosphor's spectral parameters by controlling the FWHM to be narrower (improved from 80-90 nm to a more focused distribution). This parameter change concentrates the emission in the high luminous efficiency wavelength range, thereby improving conversion efficiency without complicating the device structure.
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 provides a light-emitting device with improved color rendering, color reproducibility, and conversion efficiency, achieving higher emission intensity and narrower full width at half maximum in the emission spectrum.
Implementation Method 1
a phosphor that includes a crystal phase having a composition represented by formula (1) below, and has a minimum reflectance in a wavelength region from an emission peak wavelength of the phosphor to 800 nm that is 20% or more
Data Source
AI summary
A phosphor having a favorable emission peak wavelength, narrow full width at half maximum, and/or high emission intensity is provided. Additionally, a light-emitting device, an illumination device, an image display device, and/or an indicator lamp for a vehicle having favorable color rendering, color reproducibility and/or favorable conversion efficiency are provided. The present invention relates to a phosphor including a crystal phase having a composition represented by a specific formula, and having a minimum reflectance of 20% or more in a specific wavelength region, in which the specific wavelength region is from the emission peak wavelength of the phosphor to 800 nm, and a light-emitting device comprising the phosphor.