Reflectance-Controlled Red Phosphor for Narrow-Band LED Emission
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Solution Overview
Problem
Current red phosphors used in light-emitting devices have unclear emission intensity and conversion efficiency, with a need for improved color rendering and reproducibility, particularly in vehicle illumination and display devices.
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, Ba, 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 constructed, but the emission intensity is insufficient and conversion efficiency is poor
Solution Approach 1:
The patent changes the chemical composition parameters of the phosphor by incorporating specific ratios of Sr, Ca, Ba, Li, Al, and Eu elements to optimize emission intensity and conversion efficiency. The controlled substitution of elements in the phosphor structure allows tuning of optical properties to achieve both high emission intensity and energy efficiency.
Solution Approach 2:
The patent uses a composite phosphor material combining multiple elements (Sr, Ca, Ba, Li, Al, Eu) in specific proportions to create a new material with superior emission characteristics. This composite approach leverages the complementary properties of each element to achieve both high emission intensity and conversion efficiency that single-element phosphors cannot provide.
2Stability of the object's composition
If phosphors with broad FWHM (80-90 nm) are used, then the light-emitting device can operate, but color rendering and color reproducibility are degraded
Solution Approach 1:
The patent optimizes the compositional parameters of the phosphor to achieve a narrower FWHM while maintaining stable color rendering properties. By adjusting the ratios of activator elements (Eu, Ce, Pr, Tb, Dy) and host matrix elements, the emission spectrum is narrowed to improve color purity without sacrificing color rendering stability.
3Reliability
If Mn-activated KSF phosphor is used, then the light-emitting device can be constructed, but it causes harm to humans and the environment
Solution Approach 1:
The patent replaces harmful Mn-activated phosphors with environmentally benign alternatives using Eu, Ce, Pr, Tb, or Dy activations. This substitution eliminates the environmental and health hazards associated with Mn while maintaining or improving the optical performance and device functionality, effectively converting a harmful system into a beneficial one.
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 light-emitting devices with improved color rendering, color reproducibility, and conversion efficiency, suitable for illumination, image display, and vehicle indicator lamps, by optimizing the phosphor's composition and reflectance properties.
Implementation Method 1
a nitride phosphor that emits red light and a phosphor that emits green light, with blue light from the blue LED chip as excitation light
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.