LED Device with Transparent Resin Layer for Luminous Efficacy
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Solution Overview
Problem
Existing LED devices suffer from significant light loss due to light being reflected or scattered and re-absorbed by the phosphor layer, leading to reduced color conversion efficiency and brightness, especially in high-output conditions.
Innovation Solution
An LED device design featuring a transparent resin layer separating the LED chip from the color conversion layer, with a mean free path of phosphor particles greater than 0.8 mm and a volume 5 to 15 times that of the resin layer, reducing light loss and heat transfer, and incorporating a convex upper surface and high refractive index to enhance light extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the phosphor layer contacts the immediate vicinity of the LED chip for color conversion, then color conversion is performed efficiently, but light is reflected or scattered and re-absorbed by the LED chip causing considerable light loss
Solution Approach 1:
A transparent resin layer is introduced as an intermediary substance between the LED chip and the phosphor particles. This resin layer with refractive index of 1.5-2.0 matches the optical properties of the LED chip, serving as an optical mediator that prevents light reflection and scattering at the interface while allowing efficient energy transfer to the phosphor for color conversion.
Solution Approach 2:
The refractive index parameter of the medium between LED chip and phosphor is changed from air (n=1.0) to transparent resin (n=1.5-2.0), optimizing the optical parameter to reduce reflection and scattering. Additionally, the mean free path of phosphor particles is optimized to 0.8-1.05mm to balance color conversion efficiency and minimize light absorption losses.
2Use of energy by moving object
If the phosphor layer is placed close to the LED chip, then color conversion occurs, but heat generated by the LED chip is directly transferred to the phosphor layer causing reduction in color conversion efficiency
Solution Approach 1:
The transparent resin layer serves as a thermal intermediary with lower thermal conductivity compared to direct contact, reducing the rate of heat transfer from the LED chip to the phosphor layer while maintaining optical coupling for efficient color conversion.
Solution Approach 2:
The resin layer provides localized thermal isolation at the critical interface between LED chip and phosphor, creating a thermal barrier precisely where heat transfer would otherwise be most intense, while maintaining optical transparency for color conversion function.
3Use of energy by moving object
If phosphor particles are densely packed in the color conversion layer, then color conversion is enhanced, but light emitted by phosphor is re-absorbed by different phosphor causing light loss
Solution Approach 1:
The mean free path of phosphor particles is optimized to 0.8-1.05mm, which is a critical parameter change that balances phosphor density for adequate color conversion while maintaining sufficient spacing to prevent light re-absorption between phosphor particles.
Solution Approach 2:
The color conversion layer volume is made 5-15 times that of the transparent resin layer, providing excessive volume to ensure adequate color conversion occurs while the low phosphor concentration (long mean free path) prevents re-absorption losses.
4Power
If the LED device is designed for high output, then brightness is increased, but light loss due to reflection and re-absorption becomes more significant reducing overall efficiency
Solution Approach 1:
The transparent resin layer converts the harmful effect of light reflection at the LED chip interface into a beneficial optical coupling effect by matching refractive indices, turning potential light loss into efficient light transmission even under high power conditions.
Solution Approach 2:
Optical parameters (refractive index matching) and physical parameters (mean free path, layer volumes) are optimized to maintain high efficiency under high power operation, where these parameters become even more critical for minimizing losses at increased light intensities.
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
This design significantly reduces light loss and improves brightness and efficiency, maintaining high color conversion performance even under high current and output conditions, with luminous flux increased by 8 to 18% compared to traditional designs.
Implementation Method 1
a transparent resin layer covering a light emission surface of the LED chip
Implementation Method 2
a color conversion layer formed to be spaced apart from the LED chip by the transparent resin layer to cover the transparent resin layer and including at least one type of phosphor converting light emitted from the LED chip into light within a different wavelength region
Data Source
AI summary
There are provided a light emitting diode (LED) device including an LED chip emitting light within a specific wavelength region, a transparent resin layer covering a light emission surface of the LED chip, and a color conversion layer formed to be spaced apart from the LED chip by the transparent resin layer to cover the transparent resin layer and including at least one type of phosphor converting light emitted from the LED chip into light within a different wavelength region, wherein a mean free path of phosphor particles included in the color conversion layer is 0.8 mm or more at a temperature of 5500 K.