Oxynitride Phosphor for High Luminance and Color Rendering
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Solution Overview
Problem
Conventional phosphors used in lighting applications, such as white LEDs, suffer from inadequate red component emission, leading to poor color-rendering properties and chemical instability, which affects luminance and durability.
Innovation Solution
Development of an inorganic oxynitride phosphor with a crystal structure comprising two phases of A2Si5N8 and A2SiO4, activated with metals like Eu, Mn, or rare earth elements, which allows for higher luminance and improved color-rendering properties, and is chemically stable, using stable starting materials suitable for industrial production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional phosphors (silicate, phosphate, aluminate, sulfide) are used, then the phosphor can be easily manufactured, but the luminance decreases due to chemical instability during long-term use
Solution Approach 1:
The patent employs sialon phosphor, which is a composite material formed by reacting silicon nitride and aluminum nitride at high temperature. This composite structure combines the advantages of both nitride compounds, resulting in enhanced chemical stability and luminance durability while maintaining manufacturability through established hot pressing processes.
2Reliability
If sialon phosphor is used to improve luminance stability, then luminance durability is improved, but the red color emission and color-rendering properties are insufficient
Solution Approach 1:
The patent applies local quality by selectively doping specific regions of the sialon phosphor crystal structure with rare earth elements (Eu, Ce, Pr, Nd, Sm, Tb, Dy, Ho, Er, Tm, Yb). This localized activation allows different parts of the phosphor material to emit different wavelengths, thereby achieving both luminance stability and improved color-rendering properties including red emission.
Solution Approach 2:
The patent utilizes parameter changes by adjusting the composition ratios of host materials (silicon nitride, aluminum nitride, calcium carbonate, europium oxide) and selecting different rare earth activators to tune the emission characteristics. By varying these parameters, the phosphor can be optimized for both luminance stability and color-rendering performance.
3Adaptability or versatility
If phosphors with red color emission are developed, then color-rendering properties are improved, but chemical stability and luminance durability deteriorate
Solution Approach 1:
The patent segments the phosphor system into two distinct functional components: the sialon host matrix (providing chemical stability and structural framework) and the rare earth activator (providing color emission). This segmentation allows each component to independently fulfill its specific function, ensuring both chemical stability and color-rendering performance.
4Use of energy by moving object
If blue LED is used as excitation source, then energy efficiency is improved, but the red component emission is insufficient leading to poor color-rendering
Solution Approach 1:
The patent introduces the sialon phosphor activated with rare earth elements as an intermediary between the blue LED excitation source and the human eye. This intermediary absorbs the blue light and re-emits it across a broader spectrum including red wavelengths, thereby enabling the energy-efficient blue LED to achieve superior color-rendering properties.
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 phosphor exhibits enhanced luminance and durability, maintaining high emission efficiency and color-rendering properties, even when exposed to excitation sources, making it suitable for various display and lighting applications.
Implementation Method 1
The phosphors are excited by an excitation source having a high energy, such as a vacuum ultraviolet ray, an ultraviolet ray, an electron beam, or a blue light to emit a visible light
Implementation Method 2
The phosphors are excited by an excitation source having a high energy, such as a vacuum ultraviolet ray, an ultraviolet ray, an electron beam, or a blue light to emit a visible light
Data Source
AI summary
An object of the present invention is to provide an inorganic phosphor, particularly, an oxynitride phosphor containing alkaline earths which has a higher luminance than that of conventional sialon phosphors activated with a rare earth, and is chemically stable.By baking a raw material mixture containing at least silicon nitride powder, M element containing inorganic substance, and A element containing inorganic substance at a temperature range of 1200° C. to 2200° C. in a nitrogen atmosphere, a phosphor comprising an inorganic composition containing at least M Element, A Element, silicon, oxygen, and nitrogen (wherein M Element is one or two or more elements selected from the group consisting of Mn, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb, A Element is one or two or more elements selected from the group consisting of Mg, Ca, Sr, and Ba) and containing at least crystal having the same crystal structure as that of A2Si5N8 and A element-containing crystal is obtained.