Transparent Encapsulant for LED Light Extraction
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Solution Overview
Problem
Current LED encapsulating materials with lower refractive indices lead to significant light loss due to total internal reflection and Fresnel loss, limiting the efficiency of light-emitting diodes, and existing high refractive index materials are difficult to process for mass production.
Innovation Solution
A substantially transparent material comprising inorganic titanate or zirconate particles with a median diameter of 4 nm to 15 nm, uniformly dispersed and bonded to a compound, providing a refractive index between 2.0 and 1.4 to 1.6, which minimizes light scattering and aggregation, and has a viscosity of 30,000 centipoise or more, allowing for increased light transmission and reduced light loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If epoxy or plastic encapsulants with refractive index between 1.4 and 1.6 are used, then ease of manufacture is improved, but light extraction efficiency deteriorates due to total internal reflection and Fresnel loss
Solution Approach 1:
The patent uses a composite material consisting of a polymer matrix combined with high refractive index particles (titanium dioxide, barium sulfate, or zinc oxide) to create an encapsulant with refractive index of 1.7 or higher. This composite approach allows the material to maintain the ease of manufacture and processing benefits of polymers while achieving the high refractive index needed to reduce total internal reflection and Fresnel loss, thereby improving light extraction efficiency.
2Loss of energy
If chalcogenide glasses with high refractive index are used, then light extraction efficiency is improved, but manufacturing complexity increases making mass production difficult
Solution Approach 1:
The patent changes the material parameter from chalcogenide glass to a polymer-based composite system that achieves high refractive index (1.7 or higher) through the incorporation of high refractive index particles. This parameter change maintains the light extraction efficiency benefit while dramatically simplifying the manufacturing process, allowing for standard polymer processing techniques and mass production capability.
3Illumination intensity
If titanium dioxide particles are incorporated into polymeric host materials, then refractive index is improved, but particle aggregation occurs requiring anti-flocculant coating
Solution Approach 1:
The patent employs inexpensive anti-flocculant coatings such as silane-based coatings on the high refractive index particles. These simple, cost-effective coatings prevent particle aggregation during mixing and processing, eliminating the need for complex processing steps while maintaining the high refractive index property of the composite encapsulant material.
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 material effectively reduces light loss by minimizing total internal reflection and Fresnel loss, enhancing the efficiency of light-emitting diodes and allowing for higher light extraction with reduced power consumption and operating temperatures.
Implementation Method 1
when light crosses a boundary between media of two different refractive indices, a portion of the light is reflected back from the interface between the two media due to the difference in refractive indices. This phenomenon is known as Fresnel reflection or Fresnel loss.
Implementation Method 2
If the angle of incidence of the light to the boundary between materials is shallower than the critical angle, the light will be reflected back into the LED, due to the phenomenon of total internal reflection, thus diminishing the amount of light that can escape the LED device
Data Source
Figure 1
AI summary
The invention provides a substantially transparent material comprising particles of an inorganic titanate or an inorganic zirconate and at least one compound, wherein the particles are uniformly dispersed in the at least one compound, and wherein the particles are bonded to the at least one compound via at least one surface functional group of the particles. The invention also provides a light emitting device comprising a light emitting diode encapsulated with the substantially transparent material.