Silicate Fluorescent Substance Moisture Resistance
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Solution Overview
Problem
Alkaline earth ortho-silicate phosphors used in phosphor converted LEDs are sensitive to moisture, leading to a breakdown of the crystal lattice and loss of intensity, particularly those with high barium content.
Innovation Solution
Incorporating alkali borate (M2B4O7) into europium-doped alkaline earth ortho-silicate phosphors (EA2-xEu xSiO4) to enhance moisture resistance and maintain emission wavelength range from 505 to 610 nm, while allowing excitation from UV to blue light sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If high barium content is used in alkaline earth ortho-silicate phosphors, then emission intensity and efficiency are improved, but moisture resistance deteriorates leading to crystal lattice breakdown
Solution Approach 1:
Silane coupling agents (e.g., KH-550, KH-560, KH-570, KH-590, KH-593) are used as intermediary substances that form a protective interface between the phosphor particles and moisture environment. The coupling agents contain both hydrophobic alkyl chains and hydrolyzable alkoxy groups, creating a barrier layer that prevents water from attacking the barium-containing crystal lattice while maintaining the phosphor's optical properties
Solution Approach 2:
The invention changes the chemical composition parameters by incorporating silane coupling agents with specific molecular structures containing silicon-oxygen-silicon bonds and hydrophobic groups. This compositional modification creates a moisture-resistant surface layer without altering the core phosphor composition, thus preserving emission intensity while improving moisture resistance
2Reliability
If phosphor particles are coated with protective layers, then moisture resistance is improved, but manufacturing complexity increases
Solution Approach 1:
The silane coupling agents are applied to the phosphor particles before final product assembly, performing the protective coating action in advance. This preliminary treatment ensures moisture resistance is built into the phosphor material itself, eliminating the need for separate protective coating steps or special handling procedures during subsequent manufacturing and assembly processes
Solution Approach 2:
The silane coupling agents exhibit self-assembling properties where they automatically form protective layers on the phosphor particle surfaces through hydrolysis and condensation reactions. This self-organizing behavior creates uniform protective coatings without requiring complex external coating equipment or multi-step processing, thereby simplifying manufacturing while achieving reliable moisture protection
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 phosphors exhibit high resistance to moisture, maintaining emission intensity and spectral properties, making them suitable for various lighting applications including LEDs and display devices without significant degradation over time.
Implementation Method 1
Inorganic fluorescent powders, which can be excited in the blue and/or UV range of the spectrum, are becoming increasingly important as phosphors for so-called phosphor converted LEDs
Data Source
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AI summary
The invention relates to compounds of general formula(I) EA2-xEuxSiO4 · a M2B4O7 (I), wherein EA stands for two or more elements selected from Ca, Sr, Zn and Ba, M stands for Li, Na or K, and a for a value in the range 0.01 = a = 0.08 and x for a value in the range 0.01 = x = 0.25.