Phase Change Material White Appearance in LED Packaging
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Solution Overview
Problem
White LEDs appear non-white when turned off, which can lead to marketability issues and reduced aesthetic appeal, and existing solutions like Titanium Dioxide granules reduce lumen output by scattering light.
Innovation Solution
Incorporating phase change materials like paraffin waxes or deuterated paraffin analogs in core-shell particles within an optically functional material to create an off-state white appearance that transitions to transparency when the LED is on, minimizing light scattering and maintaining lumen output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If Titanium Dioxide granules are used to create off-state white appearance, then the LED appears white when off, but lumen output is reduced due to light scattering
Solution Approach 1:
The patent uses phase change materials that alter their optical properties based on temperature. When the LED is off, the PCM is in a solid state providing white appearance. When the LED is on and heats the PCM, it transitions to liquid state becoming transparent, allowing full light transmission and maintaining lumen output.
Solution Approach 2:
The core invention employs phase change materials (PCMs) that transition between solid and liquid states. In the solid state (LED off), the PCM appears white and provides the desired off-state appearance. In the liquid state (LED on, heated), the PCM becomes transparent, eliminating light scattering and preserving lumen output.
2Illumination intensity
If existing off-state white materials are used, then the LED appears white when off, but light scattering increases and efficiency decreases
Solution Approach 1:
The patent employs phase change materials that transition from solid to liquid state when heated by the LED operation. In the solid state, they provide white appearance; in the liquid state, they become transparent and non-scattering, thus maintaining LED efficiency during operation while providing desired aesthetic appearance when off.
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 ensures white appearance in both on and off states without impacting LED efficiency, providing improved marketability and aesthetic appeal while reducing light scattering and degradation concerns.
Implementation Method 1
The core material includes a phase change material
Implementation Method 2
a yellow emitting phosphor layer. Photons of blue light emitted by the light emitting semiconductor structure may either pass through the yellow emitting phosphor layer as blue photons or may be converted into yellow photons by the yellow emitting phosphor layer
Data Source
AI summary
Light emitting devices (LEDs) are described herein. An LED includes a light emitting semiconductor structure, a wavelength converting material and an off state white material. The light emitting semiconductor structure includes a light-emitting active layer disposed between an n-layer and a p-layer. The wavelength converting material has a first surface adjacent the light emitting semiconductor structure and a second surface opposite the first surface. The off state white material is in direct contact with the second surface of the wavelength converting material and includes multiple core-shell particles disposed in an optically functional material. Each of the core-shell particles includes a core material encased in a polymer or inorganic shell. The core material includes a phase change material.