Core-Shell Fluoride Phosphor for Color Purity and Heat Durability
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Solution Overview
Problem
Existing phosphors used in light-emitting devices for liquid crystal backlights lack high color purity, specifically requiring an emission peak with a narrow half-width, which is not adequately addressed by current fluoride phosphors.
Innovation Solution
A fluoride phosphor composition is developed with a first fluoride having a specific alkali metal, Si, Al, and Mn content, and a second fluoride deposited on its surface, which is free of Al and Mn, enhancing durability and stability through a distinct crystal structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a fluoride phosphor with specific composition (K2SiF6:Mn) is used to achieve high color purity and narrow emission peak, then color purity is improved, but durability under high-temperature conditions deteriorates
Solution Approach 1:
The patent creates a composite fluoride phosphor structure consisting of a first fluoride core (K2SiF6:Mn) and a second fluoride shell (K2SiF6) deposited on its surface. This composite structure combines the high color purity properties of the Mn-doped first fluoride with the high temperature stability of the second fluoride shell, resolving the contradiction between color purity and durability under high-temperature conditions.
Solution Approach 2:
The patent applies different material properties to different regions of the phosphor particle: the core region (first fluoride) is optimized for optical performance with Mn doping to achieve narrow emission peak, while the surface region (second fluoride shell) is optimized for thermal stability and durability. This local differentiation of material quality allows simultaneous achievement of both color purity and high-temperature durability.
2Manufacturing precision
If Al and Mn are included in the fluoride composition to achieve desired optical properties, then color purity is improved, but structural stability under high temperature deteriorates
Solution Approach 1:
The patent extracts the Al and Mn elements from the surface region of the fluoride phosphor by depositing a second fluoride shell that is substantially free of Al and Mn. This removal of potentially destabilizing elements from the surface while maintaining them in the core achieves both narrow emission peak and high-temperature structural stability.
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 resulting fluoride phosphor exhibits improved durability and maintains high color purity with a narrow emission peak, suitable for use in light-emitting devices under high-temperature conditions.
Implementation Method 1
bringing the first fluoride, a first solution containing Si and F, and a second solution containing an alkali metal into contact with each other in the presence of a reducing agent to deposit, on at least part of a surface of the first fluoride, a second fluoride
Data Source
AI summary
Provided is a fluoride phosphor having higher durability. The fluoride phosphor includes a first fluoride and a second fluoride deposited on at least part of a surface of the first fluoride. The first fluoride has a composition containing an alkali metal, Si, Al, Mn, and F, wherein, when the number of moles of the alkali metal is taken as 2, the total number of moles of Si, Al, and Mn is 0.9 to 1.1; the number of moles of Al is more than 0 and less than 0.10; the number of moles of Mn is more than 0 and less than 0.20; and the number of moles of F is 5.9 to 6.1. The second fluoride has a composition which contains an alkali metal, Si, and F, and which is substantially free of Al and Mn.