Narrow Band Red Phosphor Coating for Moisture Stability
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Solution Overview
Problem
Current narrow band red phosphors used in LED lighting are hygroscopic and prone to rapid deterioration due to moisture, oxygen, and heat, leading to reduced lumen efficacy and limited compatibility with protective coatings, and they do not effectively cover specific wavelengths needed for enhanced color gamut in display devices.
Innovation Solution
Development of a narrow-band red-emitting phosphor with a general composition MSxSeyAz:Eu, where M is Mg, Ca, or Ba, and A includes C, N, B, or cyanamide, with optional inclusion of O, F, Cl, Br, and I, and a coating of aluminum oxide or other oxides to enhance stability and emission characteristics, allowing for precise wavelength control and improved durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If narrow band red phosphors with composition MSxSey:Eu are used to achieve high lumen efficacy, then lumen efficacy is improved, but the phosphors are hygroscopic and exhibit rapid deterioration due to moisture and oxygen
Solution Approach 1:
The patent applies composite materials by combining the narrow band red phosphor MSxSey:Eu with protective coating materials such as alumina (Al2O3), silica (SiO2), or core-shell structures. This creates a composite system where the phosphor core provides high lumen efficacy while the protective shell or coating layer prevents hygroscopic deterioration, thus resolving the contradiction between achieving high lumen efficacy and maintaining reliability against moisture and oxygen.
Solution Approach 2:
The patent creates an inert environment by applying protective coatings of alumina, silica, or other oxide layers that form barrier shells around the phosphor particles. These coatings create an inert protective atmosphere that isolates the hygroscopic phosphor from moisture and oxygen in the external environment, preventing rapid deterioration while maintaining the phosphor's high lumen efficacy performance.
2Adaptability or versatility
If narrow band red phosphors are used to enhance color gamut in displays, then color gamut is improved, but the phosphors require protective coatings that may affect emission characteristics
Solution Approach 1:
The patent applies local quality by creating core-shell structures where the inner core maintains the original phosphor composition for optimal color gamut, while the outer shell provides protective functionality. Alternatively, thin protective coating layers are applied only on the surface, ensuring that the bulk emission characteristics and color gamut enhancement properties are preserved while providing necessary protection against environmental degradation.
Solution Approach 2:
The patent uses flexible shells and thin films by applying thin protective coating layers of alumina, silica, or other oxides that form conformal shells around the phosphor particles. These thin film coatings provide environmental protection while being sufficiently transparent and non-interfering to maintain the phosphor's emission characteristics and color gamut enhancement capabilities.
3Reliability
If phosphor particles are coated with protective materials to improve stability, then reliability is improved, but the coating process adds complexity to manufacturing
Solution Approach 1:
The patent applies self-service by utilizing the phosphor particles' own surface properties or by employing coating processes where the protective material self-assembles or deposits automatically under controlled conditions. The coating process is designed to be integrated into the existing phosphor synthesis or processing workflow, allowing the phosphor to essentially coat itself or receive coating in a single-step process that minimizes additional manufacturing complexity.
Solution Approach 2:
The patent applies parameter changes by optimizing coating parameters such as coating thickness, deposition temperature, and coating material composition to achieve the minimum necessary protection level. By carefully controlling these parameters, the coating process becomes more predictable and easier to manufacture, reducing complexity while still providing sufficient protection against moisture and oxygen to improve reliability.
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 stable, high-lumen efficacy red phosphors that emit light within a narrow band, enhancing color gamut and luminous efficacy in LED lighting and display applications, with improved resistance to environmental factors and compatibility with protective coatings.
Implementation Method 1
the red-emitting phosphor particles absorb radiation at a wavelength of 450 nm and emit light with a photoluminescence peak emission wavelength between about 600 nm and about 630 nm
Data Source
AI summary
A narrow band red phosphor may have a general composition MSxSeyAz:Eu, wherein M is at least one of Mg, Ca, Sr and Ba, A is at least one of C, N, B, P and a monovalent combining group NCN (cyanamide), and may in some embodiments further include one or more of O, F, Cl, Br and I. In embodiments 0.8<x+y<1.25 and 0<z≤0.05, and in some embodiments x, y and z are determined strictly by charge balancing. A white light emitting device may comprise: a blue and/or UV excitation source; a narrow band red phosphor of the present invention; and phosphors with peak emission at shorter wavelengths, such as yellow, green, yellow/green and/or blue.