LED Package Optics With Curved Reflector for Light Extraction
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Solution Overview
Problem
Light emitting diode (LED) packaging faces challenges in maximizing light extraction efficiency, reducing moisture penetration, improving structural stability against external pressure, minimizing yellowing and discoloration, and enhancing color purity by reducing side emitting light loss and chromatic aberration.
Innovation Solution
A light emitting device design incorporating a light emitting semiconductor source with a reflector, a front-light extractor, a wavelength conversion layer, and a side light extractor, where the reflector has asymmetrical reflective surfaces and a wavelength conversion layer with specific thickness and area ratios, and the side light extractor has a higher transmittance than the reflector, optimizing the curvature and positioning to enhance light extraction and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional LED package structure is used, then the device is simple to manufacture, but light extraction efficiency is insufficient
Solution Approach 1:
The patent divides the light extraction function into multiple components: a front-light extractor with first curved surface, a side light extractor with second curved surface, and a reflector. This segmentation allows each component to optimize light extraction from different directions (front and side) independently, improving overall light extraction efficiency while maintaining manufacturability through modular assembly
Solution Approach 2:
The patent introduces a side light extractor that extracts light from the side direction in addition to the conventional front light extraction. This adds a new dimension (lateral direction) to light extraction, significantly improving overall light extraction efficiency by utilizing both front and side emission paths
2Ease of manufacture
If the package structure is simplified, then manufacturing is easier, but moisture penetration resistance is reduced
Solution Approach 1:
The patent employs a nested structure where the side light extractor is positioned between the light emitting source and the reflector, with the front-light extractor covering both the light emitting source and the reflector. This nested arrangement creates multiple protective layers that extend the moisture penetration path without requiring a completely redesigned package structure, thus maintaining ease of manufacture while improving moisture resistance
Solution Approach 2:
The patent uses a reflector that reflects light (and potentially moisture) back toward the center, creating a protective effect before moisture can penetrate deeper into the device. This prior cushioning effect delays moisture penetration and protects internal components without adding complex barrier structures
3Loss of energy
If a reflector is added to improve light stability, then light extraction efficiency improves, but yellowing and discoloration increase
Solution Approach 1:
The patent applies different surface properties to different components: the front-light extractor has a first curved surface optimized for front light extraction, the side light extractor has a second curved surface for side light extraction, and the reflector has reflective properties. This local quality differentiation allows each component to perform its specific function optimally while minimizing unwanted effects like yellowing and discoloration through material selection and surface treatment
Solution Approach 2:
The patent uses curved surfaces (first curved surface on front-light extractor, second curved surface on side light extractor) instead of flat surfaces. These curved geometries improve light extraction efficiency by reducing total internal reflection and improving light coupling, thereby enhancing light stability without requiring aggressive reflector treatments that cause yellowing and discoloration
4Productivity
If side emitting light is extracted more efficiently, then light output improves, but chromatic aberration increases
Solution Approach 1:
The patent introduces a wavelength conversion layer positioned to convert wavelengths of light emitted from the light emitting source. This local wavelength conversion addresses the chromatic aberration issue by ensuring that side-emitted light (which would otherwise have different color characteristics) is converted to match the desired wavelength, thereby maintaining color purity while improving overall light output through enhanced side light extraction
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 design effectively maximizes light extraction efficiency, delays moisture penetration, improves structural stability, reduces yellowing and discoloration, and enhances color purity by optimizing the light path and reflectivity, leading to improved reliability and light quality.
Implementation Method 1
the wavelength conversion layer may include a first type of particles converting a fraction of light having a wavelength in the first wavelength band into light having a wavelength in a second wavelength band
Implementation Method 2
a reflector disposed on a side region of the light emitting source while at least partially adjoining the side region of the light emitting source
Implementation Method 3
a front-light extractor disposed on the light emitting source and the reflector and including a body including a first curved shape
Data Source
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AI summary
Disclosed is a light emitting device. The light emitting device includes a light emitting source including a light emitting semiconductor device; a reflector disposed on a side region of the light emitting source while at least partially adjoining the side region of the light emitting source; a front-light extractor disposed on the light emitting source and the reflector and including a body including a first convex shape; a wavelength conversion layer disposed in at least a region on a light path of the light emitting source; and a substrate on which the light emitting source, the reflector and the front-light extractor are disposed, wherein the reflector comprises a first reflective surface formed in at least a region thereof and including a second convex shape, the second convex shape of the first reflective surface has a radius of curvature greater than or equal to a radius of curvature of the first convex shape of the front-light extractor.