LED Wavelength Conversion Layer for Uniform Color Temperature
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Solution Overview
Problem
Conventional white LED structures exhibit non-uniform color temperature due to the higher directivity of blue light emitted by blue LED chips, leading to variations in color temperature at different angles, known as the 'yellow circle phenomenon'.
Innovation Solution
A light-emitting device with a wavelength conversion adhesive layer comprising low-concentration and high-concentration fluorescent adhesive layers, and a reflective protecting element that covers the light-emitting unit and a portion of the adhesive layer, where the width ratios of the adhesive layers and the light-emitting unit satisfy specific inequalities to ensure uniform color temperature emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-layer yellow phosphor is used on a blue LED chip, then the device structure is simple, but the color temperature of emitted light is non-uniform at different angles
Solution Approach 1:
The phosphor layer is divided into multiple layers with different yellow light conversion capabilities. The first phosphor layer has lower yellow light conversion capability while the second phosphor layer has higher yellow light conversion capability. This segmentation allows different angular regions to receive appropriate amounts of converted yellow light, achieving uniform color temperature across the emission angle.
Solution Approach 2:
Different regions of the phosphor structure are assigned different conversion properties. The first phosphor layer converts blue light to yellow light with lower conversion efficiency, while the second phosphor layer converts blue light to yellow light with higher conversion efficiency. This local differentiation in conversion capability ensures that light at different angles achieves consistent color temperature.
2Use of energy by moving object
If blue light with high directivity is used, then the LED efficiency is high, but the color temperature varies at different emission angles
Solution Approach 1:
The phosphor conversion function is segmented into two distinct layers with different conversion efficiencies. This allows the system to maintain the directional properties of blue LED light while compensating for color temperature variations through the layered phosphor structure that progressively converts blue light to yellow light at different rates.
Solution Approach 2:
The patent uses a composite phosphor structure consisting of two different phosphor materials or compositions with distinct yellow light conversion capabilities. This composite approach enables the system to simultaneously maintain high LED efficiency and achieve uniform color temperature emission across different angles.
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 achieves consistent color temperature emission at various angles by optimizing the optical path of light through different concentration fluorescent layers, thereby addressing the non-uniformity issue in conventional white LED structures.
Implementation Method 1
a layer of yellow phosphor is covered on a blue LED chip. The mechanism with which the white LED structure emits white light includes emitting blue light via a blue LED chip, wherein a portion of the blue light passes through the yellow phosphor on top and is converted into yellow light
Implementation Method 2
The reflective protecting element covers the light-emitting unit and a portion of the wavelength conversion adhesive layer
Data Source
AI summary
A light-emitting device including at least one light-emitting unit, a wavelength conversion adhesive layer, and a reflective protecting element is provided. The light-emitting unit has an upper surface and a lower surface opposite to each other. The light-emitting unit includes two electrode pads, and the two electrode pads are located on the lower surface. The wavelength conversion adhesive layer is disposed on the upper surface. The wavelength conversion adhesive layer includes a low-concentration fluorescent layer and a high-concentration fluorescent layer. The high-concentration fluorescent layer is located between the low-concentration fluorescent layer and the light-emitting unit. The width of the high-concentration fluorescent layer is WH. The width of the low-concentration fluorescent layer is WL. The width of the light-emitting unit is WE. The light-emitting device further satisfies the following inequalities: WE<WL, WH<WL and 0.8<WH/WE≤1.2. Furthermore, a manufacturing method of the light-emitting device is also provided.