Semicircular Phosphor Layers with Resin Buffer for LED Efficiency
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Solution Overview
Problem
Conventional white-color Light Emitting Devices (LEDs) face efficiency degradation due to thermal quenching and reabsorption issues, particularly in high-temperature ranges, which affects luminous efficiency and color rendering.
Innovation Solution
A light emitting device design incorporating a red phosphor with a specific sialon composition and a transparent resin intermediate layer, where the phosphors are formed into semicircular shapes with controlled diameters to suppress reabsorption and maintain high luminous efficiency and color homogeneity, even at elevated temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple phosphors are combined to achieve high color rendering and high color gamut, then color quality is improved, but luminous efficiency is degraded due to reabsorption between phosphors
Solution Approach 1:
A transparent resin intermediate layer is introduced between the red phosphor layer and green phosphor layer to prevent direct interaction and reabsorption between the phosphors. This intermediary layer allows each phosphor to emit its characteristic color without being reabsorbed by adjacent phosphors, thereby maintaining high luminous efficiency while achieving high color rendering and color gamut through the combination of multiple phosphors.
2Power
If high-power LED is used to increase output, then power is improved, but temperature rises causing thermal quenching and luminous efficiency degradation
Solution Approach 1:
The transparent resin intermediate layer acts as a thermal and optical buffer between phosphor layers, helping to manage heat distribution and reduce thermal quenching effects. This allows high-power LED operation while maintaining luminous efficiency by preventing excessive heat buildup in individual phosphor layers.
Solution Approach 2:
The patent optimizes the thickness and material properties of the transparent resin intermediate layer to control thermal and optical parameters. By adjusting these parameters, the system can operate at high power levels while maintaining luminous efficiency through reduced thermal quenching.
3Illumination intensity
If phosphor layer thickness is increased to improve emission intensity, then brightness is improved, but reabsorption increases causing luminous efficiency to degrade
Solution Approach 1:
The transparent resin intermediate layer prevents reabsorption between phosphor layers, allowing each phosphor layer to be optimized for maximum emission intensity without suffering from reabsorption losses. This enables thick phosphor layers to be used for high brightness while maintaining luminous efficiency.
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 enhances luminous efficiency and suppresses color shift, achieving high emission intensity and color rendering by restricting reabsorption and thermal quenching, thereby improving the performance of white-color LEDs.
Implementation Method 1
a light emitting element mounted on a principal surface of the board, the light emitting element emitting light having a wavelength of 250 nm to 500 nm
Implementation Method 2
a red fluorescent layer formed on the light emitting element, the red fluorescent layer including a red phosphor... a green fluorescent layer formed on the intermediate layer, the green fluorescent layer including a green phosphor
Data Source
AI summary
A light emitting device according to one embodiment includes a board; a light emitting element mounted on the board, emitting light having a wavelength of 250 nm to 500 nm; a red fluorescent layer formed on the element, including a red phosphor expressed by equation (1), having a semicircular shape with a diameter r;(M1−x1Eux1)aSibAlOcNd (1)(In the equation (1), M is an element that is selected from IA group elements, IIA group elements, IIIA group elements, IIIB group elements except Al (Aliminum), rare-earth elements, and IVB group elements),an intermediate layer formed on the red fluorescent layer, being made of transparent resin, having a semicircular shape with a diameter D; and a green fluorescent layer formed on the intermediate layer, including a green phosphor, having a semicircular shape. A relationship between the diameter r and the diameter D satisfies equation (2):2.0r(μm)≦D≦(r+1000)(μm). (2)