Phosphor Surface Treatment for LED Weather Resistance
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Solution Overview
Problem
White LED lamps using Eu and Mn-activated alkaline earth silicate, lanthanum oxysulfide, and zinc sulfide phosphors suffer from inferior weather resistance, leading to luminance deterioration under high-temperature/high-humidity environments.
Innovation Solution
A phosphor for light emitting devices is developed, where the surface of alkaline earth silicate, lanthanum oxysulfide, and zinc sulfide phosphor particles is coated with a silane coupling agent or acrylic emulsion, enhancing their weather resistance and maintaining luminance efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If Eu and Mn-activated alkaline earth silicate phosphor is used as green to yellow phosphor, then light emission efficiency and color rendering property are improved, but weather resistance deteriorates
Solution Approach 1:
A surface treatment agent is introduced as an intermediary layer between the phosphor particle and the external environment. This treatment agent prevents harmful substances from penetrating into the phosphor particle while allowing light to pass through, thereby resolving the contradiction between maintaining high light emission efficiency and improving weather resistance.
Solution Approach 2:
A thin film formed by the surface treatment agent is applied to the surface of the phosphor particle. This thin film acts as a protective barrier that maintains the phosphor's optical properties while providing resistance against high-temperature and high-humidity environments, thus improving weather resistance without sacrificing light emission efficiency.
2Illumination intensity
If Eu and Mn-activated alkaline earth silicate phosphor is used as green to yellow phosphor, then color rendering property is improved, but luminance maintenance under high-temperature/high-humidity environment deteriorates
Solution Approach 1:
The surface treatment agent serves as a protective intermediary that blocks the penetration of moisture and other harmful substances into the phosphor particle. This prevents chemical reactions that would otherwise cause luminance deterioration, thereby maintaining luminance over extended periods in high-temperature/high-humidity environments while preserving color rendering properties.
Solution Approach 2:
The surface treatment agent creates an inert protective environment around the phosphor particle, isolating it from reactive substances in the external environment. This inert barrier prevents degradation reactions, ensuring long-term luminance maintenance without affecting the phosphor's color rendering capability.
3Reliability
If surface treatment agent is applied to phosphor particle, then weather resistance is improved, but manufacturing process complexity increases
Solution Approach 1:
The surface treatment agent is applied to the phosphor particle during the manufacturing process, performing the protective function in advance before the product is put into service. This preliminary action integrates the weather resistance improvement into the existing manufacturing workflow without requiring separate post-processing steps, thereby minimizing increases in manufacturing complexity.
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 surface treatment achieves a luminance maintenance ratio of 98% or more, effectively preventing luminance reduction and color change under high-temperature/high-humidity conditions, thereby improving the durability of white LED lamps.
Implementation Method 1
the surface of alkaline earth silicate, lanthanum oxysulfide, and zinc sulfide phosphor particles is coated with a silane coupling agent or acrylic emulsion, enhancing their weather resistance and maintaining luminance efficiency
Data Source
AI summary
A phosphor for light emitting device of an embodiment includes: a phosphor particle composed of at least one selected from an alkaline earth silicate phosphor, a lanthanum oxysulfide phosphor, and a zinc sulfide phosphor; and a surface treatment agent, provided to cover a surface of the phosphor particle, of at least one selected from a silane coupling agent and an acrylic emulsion. A luminance maintenance ratio of the phosphor represented by a formula: luminance B/luminance A×100(%), is 98% or more, wherein the luminance A is a luminance of the phosphor made to emit under a condition of temperature: 23° C., humidity: 40%, and the luminance B is a luminance of the phosphor made to emit under a condition of temperature: 23° C., humidity: 40% after leaving the phosphor under a condition of temperature: 60° C., humidity: 90% for 12 hours.