Silicon Oxide Coated Phosphor for High Humidity Stability
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Solution Overview
Problem
Inorganic phosphors used in light-emitting devices deteriorate over time, especially under high-temperature, high-humidity conditions, leading to a reduction in light-emitting properties, and existing silicon dioxide coatings do not provide sufficient stability.
Innovation Solution
A coated phosphor with a silicon oxide coating having a molar ratio of oxygen to silicon (O/Si) of 2.60 or less, applied to inorganic phosphor particles, and heated under an inert atmosphere to enhance stability, with the silicon oxide coating thickness ranging from 3 nm to 200 nm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If inorganic phosphors are used to achieve wide color gamut, then color gamut is improved, but stability under high-temperature high-humidity environment deteriorates
Solution Approach 1:
The patent applies a composite coating structure consisting of multiple layers with different functions: a silicon oxide layer (with controlled O/Si ratio ≤2.60) as the primary protective barrier, optionally combined with other inorganic material layers. This composite structure provides both protection against moisture penetration and thermal stability, resolving the contradiction between maintaining wide color gamut performance and achieving reliability under harsh environmental conditions.
Solution Approach 2:
The patent controls the chemical composition parameter of the silicon oxide coating by maintaining the oxygen-to-silicon molar ratio at 2.60 or less. This specific parameter control optimizes the coating's protective properties, creating a dense structure that effectively prevents moisture and oxygen penetration while maintaining thermal stability, thus improving reliability without compromising the phosphor's optical performance.
2Duration of action of stationary object
If silicon dioxide coating is applied to suppress phosphor deterioration, then durability is improved, but stability under high-temperature high-humidity environment when LEDs are lit remains insufficient
Solution Approach 1:
The patent optimizes the silicon oxide coating by controlling the oxygen-to-silicon molar ratio to be 2.60 or less. This parameter change creates a denser, more stable coating structure that provides superior protection under high-temperature and high-humidity conditions when LEDs are operating, going beyond conventional silicon dioxide coatings.
Solution Approach 2:
The patent employs an inert atmosphere during the coating formation process to prevent unwanted chemical reactions and ensure the stability of the silicon oxide layer. This inert environment processing helps achieve the desired low O/Si ratio and prevents oxidation that would compromise the coating's protective performance under subsequent high-temperature operation.
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 coated phosphor exhibits improved stability and maintains luminous flux and chromaticity under high-temperature, high-humidity conditions, extending the lifespan of light-emitting devices.
Implementation Method 1
coating the surfaces of the inorganic phosphors with other inorganic materials has been proposed
Implementation Method 2
the coated phosphor being excellent in stability under a high-temperature, high-humidity environment in a state where LEDs are lit
Data Source
AI summary
A coated phosphor including: an inorganic phosphor particle; and a silicon oxide coating that coats the inorganic phosphor particle, wherein a molar ratio (O/Si) of an oxygen atom to a silicon atom in the silicon oxide coating through ICP emission spectroscopy of the coated phosphor is 2.60 or less.