Wavelength Conversion Ceramic Layer Phosphor Dispersion
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Solution Overview
Problem
The challenge is to prevent the thermal deterioration of phosphors in light emitting devices, particularly in high-luminance applications like automobile headlights, where the phosphors dispersed in a ceramic layer often precipitate, leading to cracks and exfoliation due to their high specific gravity and the heat generated by LED chips.
Innovation Solution
A wavelength conversion element is developed with a ceramic layer sintered from a precursor containing alkoxysilane or siloxane structures, where the phosphor particles are within 1 μm to 50 μm in diameter and concentration is 40 wt% to 95 wt%, and oxide particles are within 0.001 μm to 30 μm in diameter and 0.5 wt% to 20 wt%, optimizing dispersion and reducing crack occurrence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phosphor is dispersed in a ceramic layer to prevent thermal deterioration, then thermal stability is improved, but phosphor precipitation occurs due to high specific gravity
Solution Approach 1:
The patent introduces a dispersion medium as an intermediary substance between the phosphor particles and the ceramic layer. This dispersion medium has a specific gravity between that of the phosphor and the ceramic layer, acting as a buffer that prevents the phosphor from rapidly settling to the bottom. The intermediary medium maintains uniform distribution of phosphor particles throughout the ceramic layer during the heating process, resolving the contradiction between thermal stability and compositional uniformity.
2Productivity
If phosphor concentration in ceramic layer is increased to improve wavelength conversion, then conversion efficiency is improved, but crack generation and exfoliation occur
Solution Approach 1:
The patent optimizes the phosphor concentration parameter within a specific range (40-90 wt%) rather than using maximum concentration. This parameter change balances wavelength conversion efficiency with structural integrity. Additionally, the patent controls the specific gravity of the dispersion medium and adjusts heating conditions as parameters to prevent crack generation and exfoliation while maintaining high conversion efficiency.
3Productivity
If phosphor is placed close to LED element for efficient wavelength conversion, then conversion efficiency is improved, but thermal deterioration occurs
Solution Approach 1:
The patent creates a composite material system consisting of phosphor particles dispersed in a ceramic layer with specific thermal properties. The ceramic layer acts as a thermal management component that protects the phosphor from excessive heat while maintaining close proximity to the LED element for efficient optical coupling. This composite structure resolves the contradiction between conversion efficiency and thermal 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
This configuration ensures uniform phosphor dispersion in the ceramic layer, suppressing crack formation and exfoliation, thereby enhancing the reliability and performance of light emitting devices.
Implementation Method 1
one using a phosphor emitting a yellow light generated by being excited by a blue light emitted from an LED element to make a white light by mixing the color of each light with each other
Implementation Method 2
a ceramic layer formed on the substrate, the ceramic layer being obtained by sintering a ceramic precursor
Data Source
AI summary
A wavelength conversion element, including: a substrate; and a ceramic layer formed on the substrate, the ceramic layer being obtained by sintering a ceramic precursor; wherein the ceramic precursor is a compound selected from the group composed of alkoxysilane and a compound having a plurality of siloxane structures; a phosphor and particles of an oxide are mixed with the ceramic precursor; the phosphor has particle diameters within a range of from 1 μm to 50 μm and a concentration of the phosphor in the ceramic layer is equal to or more than 40 wt % and less than 95 wt %; and the particles of the oxide have primary particle diameters within a range of from 0.001 μm to 30 μm and a concentration within a range of from 0.5 wt % to 20 wt % in the ceramic layer.