Temperature-Sensitive Scattering Layer for White-Looking LEDs
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Solution Overview
Problem
Legacy LED diffusing layers that reduce peek-through of yellow/orange/red phosphors also decrease light production efficiency, as they become thicker or denser, leading to a tradeoff between cosmetic appearance and efficiency.
Innovation Solution
A temperature-sensitive low-index particle layer is used in LED devices, which appears white at room temperature while maintaining efficiency by varying the index of refraction with temperature, allowing for a thin layer to achieve scattering without significant light loss during operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the diffusing layer is made thicker or denser to reduce phosphor peek-through, then cosmetic appearance is improved, but light production efficiency deteriorates
Solution Approach 1:
The patent applies the dynamics principle by using a temperature-sensitive scattering layer that dynamically changes its optical properties. At room temperature (off-state), the layer has high scattering capability to provide white appearance and hide phosphors. When the LED operates and heats up, the scattering layer's index of refraction changes, reducing scattering and allowing efficient light transmission. This dynamic adaptation resolves the contradiction between cosmetic appearance and light efficiency.
Solution Approach 2:
The patent employs parameter changes by utilizing materials whose index of refraction changes with temperature. The scattering layer is formulated with particles and binding materials selected to have temperature-dependent refractive index properties. As temperature increases during LED operation, the refractive index mismatch decreases, reducing scattering and improving light transmission efficiency while maintaining the white appearance effect at lower temperatures.
2Shape
If a diffusing layer is added to cover phosphors, then cosmetic appearance is improved, but light transmission efficiency deteriorates
Solution Approach 1:
The temperature-sensitive scattering layer dynamically adjusts its scattering properties based on operating conditions. During LED operation, the heat generated causes the scattering layer to become more transparent, minimizing energy loss from light scattering. This resolves the contradiction by making the cosmetic enhancement temporary and condition-dependent rather than permanent.
Solution Approach 2:
The patent utilizes phase transitions or state changes in the scattering layer materials. The binding material and scattering particles are selected to undergo changes in their optical properties at operating temperatures, effectively transitioning from a high-scattering state at room temperature to a low-scattering state during operation, thereby reducing energy loss while maintaining cosmetic benefits.
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 enables a white appearance without reducing light-emitting efficiency, as the layer transitions to transparency at operating temperatures, maintaining high efficiency and aesthetic appeal.
Implementation Method 1
a light-scattering layer disposed in the path of light emitted by the semiconductor light emitting device wherein the light-scattering layer comprises a binding material having a first index of refraction at a first temperature and a concentration of scattering agents having a second index of refraction at the first temperature
Implementation Method 2
the index of refraction of the scattering agents at the first temperature is lower than the index of refraction of the binding material at the same temperature
Data Source
AI summary
Systems for LED illumination products. Solutions to the problems attendant to delivering a white-appearing LED product without diminishing efficiency of white light generation are presented. Devices are designed and manufactured that include a specially-formulated off-state white-appearing layer to the LED apparatus. The composition of the specially-formulated off-state white-appearing layer is tuned for high-efficiency during the on-state.