Red Phosphor for Wide Color Gamut White LEDs
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Solution Overview
Problem
Conventional white light sources for illuminating devices and liquid crystal display devices, particularly those using YAG:Ce phosphor or green and red sulfide phosphors, suffer from bluish tint, narrow color gamut, luminance degradation, and complexity in mixing fluorescent materials, making it difficult to achieve pure white illumination and high-quality color reproducibility.
Innovation Solution
A red phosphor composed of europium (Eu), silicon (Si), aluminum (Al), oxygen (O), and nitrogen (N) with specific proportions, including strontium (Sr) as element A, is developed, which is synthesized using a method involving carbonate compounds, europium nitride, silicon nitride, and melamine, and then calcined to produce a high-luminance, long-wavelength emission capable of producing bright white light with a wide color gamut.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If YAG:Ce phosphor is used in white light source, then the structure is simple, but the color gamut is narrow and white light quality is poor
Solution Approach 1:
The patent combines YAG:Ce phosphor with red phosphor materials (such as CaAlSiN3:Eu, Sr2Si5N8:Eu, or BaMgAl10O17:Eu) to create a composite phosphor system. This merging approach maintains the structural simplicity of using phosphor coatings while achieving expanded color gamut and improved white light quality through the complementary emission spectra of the combined phosphors.
Solution Approach 2:
The invention employs composite phosphor materials consisting of multiple phosphor types with different emission characteristics. The composite system includes yellow-emitting YAG:Ce phosphor and red-emitting phosphors, creating a material composition that delivers both broad spectral coverage and high color rendering performance while maintaining manufacturing simplicity.
2Illumination intensity
If green and red sulfide phosphors are used, then color gamut is improved, but luminance degrades over time due to hydrolysis
Solution Approach 1:
The patent transitions from sulfide-based phosphors to nitride-based phosphors (such as CaAlSiN3:Eu, Sr2Si5N8:Eu, BaMgAl10O17:Eu). This parameter change in chemical composition replaces the hydrolytically unstable sulfide group with hydrolytically stable nitride groups, eliminating the hydrolysis problem while maintaining red emission characteristics and color gamut performance.
Solution Approach 2:
The invention replaces short-lived sulfide phosphors with long-lived nitride phosphors that resist degradation. The nitride phosphors provide comparable or superior color gamut performance but with significantly improved temporal stability and resistance to environmental degradation, ensuring long-term luminance maintenance.
3Illumination intensity
If multiple fluorescent materials are mixed, then color performance is improved, but manufacturing complexity increases
Solution Approach 1:
The patent merges multiple phosphor materials into a single composite phosphor layer that can be applied as one coating. This approach maintains the color performance benefits of multiple phosphors while simplifying manufacturing by eliminating the need for separate application processes for each phosphor type.
Solution Approach 2:
The composite phosphor system serves multiple functions simultaneously: YAG:Ce provides yellow emission for broad spectral coverage, while integrated red phosphors provide red emission for color gamut expansion. This multi-functional integration achieves high color performance without requiring separate manufacturing steps for different phosphor layers.
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 red phosphor achieves luminous intensity 1.5 times higher than YAG:Ce at 662 nm, providing bright white light with a wide color gamut, enabling high-luminance pure white illumination and superior color reproducibility in illuminating devices and liquid crystal display devices.
Implementation Method 1
A red phosphor of an embodiment contains an element A, europium (Eu), silicon (Si), aluminum (Al), oxygen (O), and nitrogen (N) in the proportions of the composition formula (1)... By the inclusion of strontium and europium, the red phosphor of the configuration above is capable of red emission, and, because of the foregoing composition, luminous intensity is strong and luminance is high.
Implementation Method 2
A carbonate compound of element A, europium nitride, silicon nitride, and aluminum nitride are prepared so as to contain the element A, europium (Eu), silicon (Si), and aluminum (Al) at the proportions of the composition formula (1). These are mixed with melamine to produce a mixture. The mixture is calcined, and the resulting calcined product is pulverized.
Data Source
AI summary
A compound is provided containing silicon, aluminum, strontium, europium, nitrogen, and oxygen is used that enables a red phosphor having strong luminous intensity and high luminance to be obtained, and that enables the color gamut of a white LED to be increased with the use of red phosphor. The red phosphor contains element A, europium, silicon, aluminum, oxygen, and nitrogen at the atom number ratio of the following formula: [Am−x)Eux]Si9AlyOnN [12+y−2(n−m)/3]. The element A in the formula is at least one of magnesium, calcium, strontium, and barium, and m, x, y, and n in the formula satisfy the relations 3<m<5, 0<x<1, 0<y<2, and 0<n<10.