Wavelength Converting Element Refractive Index Matching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing lighting devices with wavelength converting elements using phosphors with metal-ion activators excited via partially forbidden transitions suffer from high scattering losses due to refractive index mismatches between the phosphor and the encapsulant, leading to inefficient light conversion and increased thickness requirements.
Innovation Solution
A lighting device with a wavelength converting element comprising a Mn(IV)-activated fluoride compound compounded with a polymer, where the refractive index difference between the phosphor and the polymer is minimized to less than 0.1, preferably less than 0.05, to reduce scattering losses and enhance light conversion efficiency, using materials like K2SiF6:Mn(IV) and Na3Li3Al2F12:Mn(IV) with a fluorine-containing polymer, such as a co-polymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If phosphors with metal-ion activators excited via partially forbidden transitions are used, then light conversion can be achieved, but scattering losses increase due to refractive index mismatch
Solution Approach 1:
The patent changes the refractive index parameter of the encapsulant material to match that of the phosphor. By selecting an encapsulant with a refractive index between 1.33-1.47, the patent optimizes the optical parameter to minimize scattering losses while maintaining efficient light conversion through the phosphor's partially forbidden transition characteristics.
Solution Approach 2:
The patent employs a composite encapsulant composition comprising a polymer matrix combined with specific additives or compounds that adjust the overall refractive index to match the phosphor. This composite approach allows precise tuning of the encapsulant's optical properties to reduce scattering while maintaining structural integrity and other required functions.
2Use of energy by moving object
If long interaction paths are used to achieve sufficient light conversion, then conversion efficiency improves, but scattering losses increase
Solution Approach 1:
By optimizing the refractive index parameter of the encapsulant to match the phosphor, the patent reduces scattering losses per unit length. This allows the use of thinner encapsulant layers with shorter interaction paths while maintaining sufficient light conversion efficiency, thereby resolving the contradiction between conversion efficiency and path length.
3Ease of manufacture
If refractive index mismatch between phosphor and encapsulant is large, then manufacturing is easier, but scattering losses increase
Solution Approach 1:
The patent establishes a specific refractive index range (1.33-1.47) for the encapsulant that balances manufacturability with optical performance. This parameter optimization allows selection from a practical range of materials while ensuring minimal scattering losses through refractive index matching with the phosphor.
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 significantly reduces scattering losses and achieves efficient light conversion with a compact design, suitable for use in various lighting devices, including LEDs, by matching the refractive indices of the phosphor and polymer, resulting in a cost-effective and efficient wavelength converting element with low scattering.
Implementation Method 1
a phosphor with a metal-ion activator which is excitable via a partially forbidden electronic transition
Implementation Method 2
a wavelength converting element arranged to convert at least part of the light with the primary wavelength into light with a secondary wavelength
Data Source
Figure 1~2
AI summary
The invention relates to a lighting (1) device comprising a light source (2) and a wavelength converting element (7), which comprises a phosphor compounded with a polymer. The phosphor contains a metal- ion activator which is excitable via a partially forbidden electronic transition. The phosphor and the polymer being chosen such that the difference in their refractive index is smaller than 0.1. Due to this choice, scattering in the wavelength converting element (7) remains at minimum. Interesting wavelength converting elements (7) are obtained when using phosphors comprising specific Mn(IV)-activated fluoride compounds and specific fluorine-containing polymers.