LED Adhesive Layer Refractive Index Matching
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Solution Overview
Problem
Conventional glue layers in LEDs have a low refractive index, leading to reduced power transmission and photon leakage, which decreases the total flux emitted in the forward direction due to Total Internal Reflection and channel behavior.
Innovation Solution
The use of an adhesive layer with short chain molecules or a nano-structure layer at the interface between the substrate and wavelength converting layer, reducing the adhesive layer thickness to less than 100 nm or approaching zero, and modifying the critical angle for Total Internal Reflection to enhance light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional glue layer is used between substrate and wavelength converting layer, then the layers can be bonded together, but the low refractive index of the glue layer causes Total Internal Reflection and reduces power transmission
Solution Approach 1:
The patent changes the refractive index parameter of the adhesive layer by using materials with higher refractive index (e.g., epoxy resin with refractive index of 1.5-1.7, matching closer to sapphire substrate and phosphor materials). This parameter change reduces the refractive index mismatch, minimizing Total Internal Reflection and improving power transmission from substrate to wavelength converting layer while maintaining bonding function.
2Strength
If a conventional glue layer is used between substrate and wavelength converting layer, then the layers can be bonded together, but the glue layer acts as a channel to guide photons along the interface, causing photon leakage from the LED edge
Solution Approach 1:
The patent modifies the refractive index parameter of the adhesive layer to match more closely with the substrate and phosphor materials. This reduces the formation of optical channels at the interface that would otherwise guide photons laterally and cause edge leakage. The optimized refractive index minimizes total internal reflection at the adhesive layer interfaces, preventing photon channeling and leakage.
3Strength
If a conventional glue layer with lower refractive index is used, then bonding is achieved, but the critical angle for Total Internal Reflection is low (∼52 degrees), reducing forward light flux emission
Solution Approach 1:
The patent changes the refractive index parameter of the adhesive layer from low (∼1.4-1.5) to higher values (1.5-1.7) that better match the substrate and phosphor materials. This increases the critical angle for Total Internal Reflection, allowing a broader range of light angles to transmit through the adhesive layer in the forward direction, thereby increasing forward light flux and overall LED productivity.
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 approach increases the optical power transmission and reduces photon leakage, resulting in improved forward light flux emission by LEDs.
Implementation Method 1
The adhesive layer may include a plurality of short chain molecules... increases the optical power transmission
Implementation Method 2
modifying the critical angle for Total Internal Reflection to enhance light emission... reduces photon leakage
Data Source
AI summary
An adhesive layer is disclosed and may include a plurality of short chain molecules, each of the plurality of the short chain molecules including a first end and a second end such that the distance between the first end and second end is less than 100 nm and such that first end is configured to attach to a first surface and the second end is configured to attach to a second surface.