Red Phosphor Composition for Narrow-Band LED Emission
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Solution Overview
Problem
The existing red phosphors used in light emitting devices have issues with low visual sensitivity for red color, decreased lumen equivalent, and degraded color rendering properties, particularly due to their long emission peak wavelength and large full width half maximum.
Innovation Solution
A light emitting device incorporating a phosphor with a specific crystal phase composition, represented by the formula MA:MB:MC:Re, where MA includes Ca, MB is predominantly Li, MC is predominantly Al, and Re is predominantly Eu, with a controlled molar ratio and impurity phase intensity, achieving an emission peak wavelength between 620 nm and 645 nm and a full width half maximum of 70 nm or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a phosphor with long emission peak wavelength (about 650 nm) is used, then the red color emission is achieved, but the visual sensitivity for red color decreases and lumen equivalent decreases
Solution Approach 1:
The patent changes the emission peak wavelength parameter from about 650 nm to a shorter wavelength within the range of 610-640 nm by adjusting the phosphor composition (formula 1 with specific MA, MB, MC, Re elements and their ratios). This parameter change maintains red color emission while improving visual sensitivity and lumen equivalent, as the human eye is more sensitive to red light in this wavelength range.
2Illumination intensity
If a phosphor with long emission peak wavelength (about 650 nm) is used, then the red color emission is achieved, but the color rendering property or color reproducibility degrades
Solution Approach 1:
The patent adjusts the emission peak wavelength parameter to 610-640 nm and controls the full width half maximum (FWHM) to 70 nm or less by optimizing the phosphor composition. This creates a more precise emission spectrum that improves color rendering and reproducibility while maintaining adequate red color emission.
3Illumination intensity
If a phosphor with large full width half maximum (80 nm to 90 nm) is used, then the emission intensity is sufficient, but the color purity and visual sensitivity decrease
Solution Approach 1:
The patent reduces the full width half maximum (FWHM) parameter from 80-90 nm to 70 nm or less by optimizing the phosphor composition (formula 1 with specific element ratios and controlled impurity phases). This narrowing of the emission spectrum improves color purity and visual sensitivity while maintaining sufficient emission intensity through compositional optimization.
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 properties, high visual sensitivity for red colors, and enhanced luminous efficiency, suitable for lighting and display applications, including indicator lamps for vehicles.
Implementation Method 1
a phosphor that contains a crystal phase having a composition represented by the following formula (1)... a light emitting device including the phosphor... blue light from the blue LED chip as excitation light
Data Source
AI summary
A phosphor which comprises a crystal phase that has a composition represented by the following formula [1]; and a light emitting device which is provided with this phosphor.(MA includes one or more elements selected from the group consisting of Ca, Ba, Na, K, Y, Gd, and La,MB includes one or more elements selected from the group consisting of Li, Mg, and Zn,MC includes one or more elements selected from the group consisting of Al, Si, Ga, In, and Sc,X includes one or more elements selected from the group consisting of F, Cl, Br, and I,Re includes one or more elements selected from the group consisting of Eu, Ce, Pr, Tb, and Dy, anda, b, c, d, e, f, x, and y respectively satisfy the following expressions.0.8≤a≤1.21.4≤b≤2.61.4≤c≤2.61.1≤d≤2.91.1≤e≤2.90.≤f≤0.10.<x≤0.20.<y≤0.7)