Hemispherical LED Stack Eliminates Air Gaps for Light Extraction
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Solution Overview
Problem
Conventional light emitting devices with air layers between lenses and color conversion materials suffer from light loss due to total reflection, reduced resin transmission rates, and decreased luminance efficiency, and struggle to provide specific emission patterns due to flat mounting substrates.
Innovation Solution
A light emitting device with a concave substrate and a hemispherical stack structure comprising a blue LED, a deformable resin sheet, a hemispherical transmissive layer, a color conversion layer with fluorescent material, and a transparent outer layer, which minimizes air gaps and enhances light extraction efficiency while allowing for varied substrate shapes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If an air layer is provided between the lens and the color conversion material, then the device structure is simplified, but light loss due to total reflection increases and luminance efficiency decreases
Solution Approach 1:
The invention extracts and removes the air layer from the interface between the lens and color conversion material. By eliminating this intermediate layer, the patent prevents total internal reflection at the air-resin interface, thereby reducing light loss and improving luminance efficiency while maintaining structural simplicity.
Solution Approach 2:
The invention merges the lens and color conversion material into direct contact, eliminating the air gap between them. This merging of interfaces ensures continuous light transmission from the blue LED through the lens directly into the color conversion material, preventing light loss due to total reflection while simplifying the overall device structure.
2Ease of manufacture
If a flat mounting substrate is used, then the manufacturing process is simplified, but specific emission patterns cannot be provided
Solution Approach 1:
The invention introduces a concave portion with a curved surface into the mounting substrate. This curvature is formed in the region corresponding to the blue LED chip, allowing the substrate to provide specific emission patterns while maintaining ease of manufacture through standard molding processes. The curved surface enables controlled light extraction and directional emission.
Solution Approach 2:
The invention applies local quality by creating a concave portion only in the specific region where the blue LED chip is mounted, while the rest of the substrate remains flat. This localized curvature modification allows the substrate to provide specific emission patterns for the LED region without complicating the overall manufacturing process.
3Ease of manufacture
If the compounding ratio of fluorescent material to resin is determined in advance, then the manufacturing process is simplified, but variations in emission color cannot be reduced
Solution Approach 1:
The invention applies local quality by varying the compounding ratio of fluorescent material to resin in different regions of the color conversion material. Specifically, the compounding ratio is adjusted according to the emission wavelength of the blue LED chip, allowing precise control over emission color while maintaining a relatively simple manufacturing process through co-molding techniques.
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 high-intensity light output with improved luminance efficiency and specific emission patterns without color shift, effectively addressing the limitations of conventional devices.
Implementation Method 1
a yellow fluorescent material such as YAG doped with Ce... a fluorescent material absorbing the visible light and emitting fluorescent light of a longer wavelength than the absorbed light
Implementation Method 2
convex lenses formed at the portions where the blue LED chips are mounted... a first transmissive layer that is formed in a hemispherical shape... and transmits the first light
Implementation Method 3
light loss due to total reflection at the interface between the lens and the color conversion material containing a fluorescent material
Data Source
AI summary
A light emitting device includes: a substrate having a concave portion formed on a surface thereof; a light emitting element emitting a first light which is a blue light or a near-ultraviolet light; a resin sheet being a deformable resin sheet formed on the substrate so as to cover the light emitting element; a first transmissive layer formed in a hemispherical shape on the first region of the resin sheet, and transmitting the first light; a color conversion layer including a fluorescent material that converts the first light into a second light of a different wavelength from that of the first light and a transmissive material that transmits the first light, the color conversion layer covering the first transmissive layer in such a manner that an end portion reaches an upper face of the resin sheet; and a second transmissive layer covering the color conversion layer in such a manner that an end portion reaches the upper face of the resin sheet, and transmitting the first light and the second light.