Fluorescent Material Mn4+ Concentration Gradient for LED Reliability
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Solution Overview
Problem
Conventional fluoride fluorescent materials activated with Mn4+ in light emitting devices suffer from optical output reduction and chromaticity deviation due to reaction with atmospheric moisture, leading to manganese dioxide formation, which complicates their application in reliable backlight systems for liquid crystal displays.
Innovation Solution
A light emitting device design featuring a sealing member with a fluoride fluorescent material having a chemical composition A2[M1-bMn4+bF6], where the tetravalent manganese ion concentration is lower in the surface region than in the inner region, preventing moisture-induced manganese dioxide formation and maintaining optical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fluoride fluorescent material activated with Mn4+ is used to achieve narrow emission peak and high color purity, then color reproduction is improved, but optical output reduction and chromaticity deviation occur due to reaction with atmospheric moisture
Solution Approach 1:
The fluorescent material particles are designed with non-uniform Mn4+ concentration distribution, where the surface region has lower Mn4+ concentration than the inner region. This local quality variation protects the surface from moisture-induced blackening while maintaining the inner core's high color purity and narrow emission peak characteristics.
Solution Approach 2:
The fluorescent material is formulated as a composite structure combining fluoride host material with Mn4+ activator, where the compositional gradient (higher Mn4+ in inner region, lower Mn4+ in surface region) creates a functional composite that simultaneously achieves color purity and moisture resistance.
2Reliability
If sealing material containing fluorescent material is applied to protect the light emitting element, then element protection is improved, but optical output reduction occurs due to Mn4+ reaction with moisture
Solution Approach 1:
The fluorescent material particles are designed with non-uniform Mn4+ concentration distribution, where the surface region has lower Mn4+ concentration than the inner region. This local quality variation protects the surface from moisture-induced blackening while maintaining the inner core's high color purity and narrow emission peak characteristics.
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 effectively suppresses optical output reduction and chromaticity deviation, ensuring long-term reliability and durability of the light emitting device by preventing manganese dioxide formation, thus enhancing its suitability for demanding applications like liquid crystal display backlights.
Implementation Method 1
fluorescent material with a narrow half width of the emission peak has been in demand
Data Source
AI summary
A light emitting device includes a package having side walls which define a recess, a light emitting element arranged in the recess, and a sealing member which seals the light emitting element. The sealing member includes a first portion which contains a fluorescent material and covers the light emitting element, and a second portion which does not contain a fluorescent material and is arranged over the first portion. The fluorescent material is a fluoride fluorescent material activated with tetravalent manganese represented by the following formula (I). The particles of the fluorescent material has a surface region with a tetravalent manganese ion concentration is lower than inner side.A2[M1-bMn4+bF6] (I)In the formula (I), A is a cation which contains K+ and may contain at least one selected from the group consisting of Li+, Na+, Rb+, Cs+, and NH4+, M is at least one of 15 Group 4 and Group 14 elements, and 0<b<0.2.