Wavelength Conversion Member With Controlled Porosity for Light Coupling
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Solution Overview
Problem
Existing wavelength conversion members, such as those made of single crystal or polycrystalline phosphors, suffer from low light coupling efficiency due to the absence of grain boundaries and low porosity, causing excitation light and fluorescence to spread over a wide area and not being effectively focused by lenses.
Innovation Solution
A wavelength conversion member composed of a sintered body of phosphor with controlled pore and grain diameters, where the average pore diameter ranges from 0.28 to 0.98 μm, pore area ratio from 0.04% to 2.7%, and grain diameter from 1 to 3 μm, incorporating grain boundaries and pores to scatter light and enhance coupling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single crystal phosphor or polycrystalline phosphor with low porosity is used as a wavelength conversion member, then thermal conductivity is maintained and excitation light backscatter is suppressed, but light extraction area expands and coupling efficiency with optical systems decreases
Solution Approach 1:
The patent applies porous materials by introducing pores with specific diameter ranges (0.28-0.98 μm) and area ratios (0.04%-2.7%) into the sintered body of phosphor. These pores serve dual functions: they scatter light to suppress expansion of the light extraction area, improving coupling efficiency, while the controlled porosity (not exceeding 3%) maintains adequate thermal conductivity. This resolves the contradiction by using a precisely controlled porous structure that benefits both optical and thermal performance.
2Productivity
If pores are introduced into the wavelength conversion member to scatter light, then light coupling efficiency is improved, but thermal conductivity decreases due to air-filled pores
Solution Approach 1:
The patent applies parameter changes by precisely controlling the pore diameter (0.28-0.98 μm) and pore area ratio (0.04%-2.7%) to optimize the balance between light scattering and thermal conductivity. Additionally, the porosity is constrained to not exceed 3%, and the sintering process is optimized to achieve dense packing. These parameter optimizations ensure that light scattering efficiency is maximized while thermal conductivity degradation is minimized, resolving the contradiction between optical and thermal performance.
3Productivity
If the light extraction area is reduced to improve coupling efficiency, then light extraction efficiency decreases, but if the area is maintained, then coupling efficiency remains low
Solution Approach 1:
The patent applies local quality by creating non-uniform pore distribution and varying pore sizes (0.28-0.98 μm) within the sintered body of phosphor. This local variation in pore characteristics enables different regions to perform different functions: some areas provide strong light scattering to concentrate light paths, while other areas maintain adequate light extraction. The grain size (1-3 μm) is also controlled to create local optical field variations that improve both coupling efficiency and light extraction efficiency simultaneously.
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 suppresses the expansion of the light extraction area, improving light coupling efficiency with optical systems and maintaining high internal quantum efficiency even under elevated temperatures.
Implementation Method 1
incorporating grain boundaries and pores to scatter light and enhance coupling efficiency
Implementation Method 2
a wavelength conversion member that absorbs excitation light and emits light with a different wavelength
Data Source
AI summary
A wavelength conversion member includes a sintered body of a phosphor. An average diameter of pores in an arbitrary cross section falls within a range of not less than 0.28 μm and not more than 0.98 μm. A ratio of an area of pores to a whole area in an arbitrary cross section falls within a range of not less than 0.04% and not more than 2.7%. An average diameter of grains of the phosphor in an arbitrary cross section falls within a range of not less than 1 μm and not more than 3 μm.