Scattering Layer Particle Size for LED Color Uniformity
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Solution Overview
Problem
Existing light emitting devices face challenges in simultaneously improving color unevenness and light extracting efficiency due to differences in emission intensity distribution between semiconductor light emitting elements and fluorescent material layers, leading to suboptimal chromaticity and brightness.
Innovation Solution
A light emitting device design incorporating a semiconductor light emitting element and a fluorescent material layer with a scattering layer that selectively scatters primary light using particles with a mean particle size between 20 nm and 0.4×λ/π, where λ is the primary light wavelength, to control emission intensity distribution and reduce excessive scattering, thereby enhancing light extraction and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If scattering particles are dispersed in the transparent resin to improve color unevenness, then color uniformity is improved, but light extracting efficiency decreases
Solution Approach 1:
The patent applies local quality by creating a scattering layer with specific particle size distribution (20nm to 0.4×λ/π) that is positioned between the semiconductor light emitting element and the fluorescent material layer. This localized scattering structure selectively scatters primary light while allowing secondary light to pass through, thereby improving color uniformity without significantly reducing overall light extracting efficiency.
Solution Approach 2:
The patent changes the particle size parameter of scattering particles to a specific range (20nm to 0.4×λ/π) to optimize the scattering effect. By controlling the particle size parameter, the scattering layer achieves effective scattering of primary light for color uniformity while minimizing excessive scattering that would reduce light extracting efficiency.
2Loss of energy
If particle size is reduced to suppress light scattering, then light extracting efficiency is improved, but color unevenness increases
Solution Approach 1:
The patent optimizes the particle size parameter to a specific range (20nm to 0.4×λ/π) that balances light scattering suppression with color uniformity. This parameter optimization ensures that particles are small enough to reduce excessive scattering and maintain light extracting efficiency, while still providing sufficient scattering to uniformize color distribution.
Solution Approach 2:
The patent uses composite materials by combining scattering particles with transparent resin to form a scattering layer. This composite structure provides the necessary scattering function for color uniformity while the transparent resin matrix maintains high light transmitting properties, achieving both color uniformity and light extracting efficiency.
3Illumination intensity
If transparent resin is used to coat semiconductor light emitting element and fluorescent material layer, then optical properties are improved, but emission intensity distribution difference causes color unevenness
Solution Approach 1:
The patent introduces a scattering layer as an intermediary component between the semiconductor light emitting element and the fluorescent material layer. This scattering layer mediates the light from both sources, uniformizing their emission intensity distributions and eliminating color unevenness while maintaining the excellent optical properties provided by the transparent resin.
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 effectively suppresses color unevenness and maintains high light extracting efficiency by selectively scattering primary light more than secondary light, resulting in a brighter output with reduced color variation.
Implementation Method 1
a scattering layer, in which particles are dispersed in a transparent medium, on the light emitting side of the fluorescent material layer
Implementation Method 2
a fluorescent material layer formed around the semiconductor light emitting element by various methods such as potting, screen printing or the like
Data Source
AI summary
A light emitting device capable of improving both color unevenness and emission output power is provided. The light emitting device includes a semiconductor light emitting element including a semiconductor layer that emits primary light; and a fluorescent material layer disposed on the light emitting side of the semiconductor light emitting element, that absorbs a part of the primary light and emits secondary light having a wavelength longer than that of the primary light; and emits light of blended color of the primary light and the secondary light of the light emitting element, and further includes a scattering layer in which particles having a mean particle size D that satisfies the inequality: 20 nm<D≦0.4×λ/π are dispersed in a transparent medium.