Porous Ceramic Light Scattering for LED Color Homogeneity
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Solution Overview
Problem
Existing light emitting devices using wavelength converting materials suffer from color homogeneity issues due to uneven light scattering, leading to the formation of a 'yellow ring' around the device, and current manufacturing processes struggle to control porosity effectively for mass production.
Innovation Solution
A light emitting device featuring a porous ceramic element with an average pore diameter of 2 μm to 10 μm, which scatters blue primary radiation and yellow secondary radiation homogeneously, preventing the formation of a yellow ring, and a manufacturing method involving ceramic particles and polymeric particles to achieve controlled porosity during sintering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If scattering is introduced in the ceramic element to prevent yellow ring formation, then color homogeneity is improved, but manufacturing control becomes difficult due to porosity variations
Solution Approach 1:
The patent introduces controlled porosity into the ceramic element to provide light scattering centers. By carefully controlling the pore size (0.1-10 μm) and distribution, the ceramic scatters blue light uniformly throughout the volume, preventing the yellow ring effect while maintaining manufacturability through established porous ceramic fabrication techniques
Solution Approach 2:
The patent optimizes specific parameters including pore diameter (0.1-10 μm), porosity level (1-50%), and ceramic composition to achieve the desired balance between light scattering and manufacturing control. These parameter ranges are specifically selected to ensure uniform color output while remaining compatible with standard ceramic processing methods
2Stability of the object's composition
If small pore sizes are used to achieve homogeneous scattering, then color homogeneity is improved, but manufacturing robustness deteriorates due to sensitivity to temperature variations
Solution Approach 1:
The patent identifies optimal parameter ranges where manufacturing robustness and color homogeneity are both achieved. Specifically, pore sizes of 0.1-10 μm and porosity levels of 1-50% provide sufficient scattering while being tolerant to normal sintering temperature variations, making the process suitable for mass production
Solution Approach 2:
The patent employs a moderate level of porosity (1-50%) rather than extreme values. This partial action approach ensures adequate light scattering for color homogeneity while maintaining enough structural integrity and process tolerance for reliable manufacturing, avoiding the sensitivity issues associated with very low porosity
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 provides a homogenous color impression and enhanced light emission efficacy while allowing for cost-effective and robust mass production of light emitting devices with controlled porosity and scattering.
Implementation Method 1
The porous ceramic element has an average pore diameter of from 2 μm to 10 μm, which scatters blue primary radiation and yellow secondary radiation homogeneously
Implementation Method 2
convert part of the emitted light to yellow light (wavelength spectrum at about 580 nm) via wavelength converting materials, such as for example modified YAG:Ce based phosphors
Data Source
AI summary
The present invention relates to a light emitting device (100) comprising at least one light emitting diode (101) and at least one porous ceramic element (102), which ceramic element (102) is arranged to receive light from the light emitting diode(s) (101). The present invention also relates to methods for the manufacture of the light emitting device (100) and of the porous ceramic element (102).