Phosphor-Converted Blue LED Luminous Flux Enhancement
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Solution Overview
Problem
Conventional blue LEDs have limited luminous flux due to the human eye's varying sensitivity to different wavelengths, making them appear less bright compared to green LEDs, despite higher radiant flux, and existing solutions like using longer wavelength LEDs or increasing power output are not optimal for all applications.
Innovation Solution
Incorporating a small amount of green or yellow phosphor materials in blue LEDs to down-convert a small percentage of blue light into green or yellow light, which is then perceived as blue, enhancing the luminous flux by leveraging the human eye's greater sensitivity to these wavelengths, while maintaining the blue color appearance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional blue LEDs are used to emit blue light, then the device structure is simple, but the luminous flux is limited due to human eye sensitivity
Solution Approach 1:
The patent combines blue LED material with green or yellow phosphor materials to create a composite light-emitting structure. The blue LED chip emits blue light, and the phosphor materials convert some blue light to green or yellow light, creating a composite emission that leverages human eye sensitivity to achieve higher luminous flux while maintaining blue color perception
Solution Approach 2:
The patent changes the optical parameters of the LED system by introducing phosphor materials with specific emission wavelengths (green: 500-545nm, yellow: 560-580nm) and controlling their concentration (0.1-5% by weight). This parameter optimization allows the device to achieve peak luminous flux enhancement while maintaining blue color appearance
2Illumination intensity
If phosphor materials are added to down-convert blue light, then luminous flux increases, but the device structure becomes more complex
Solution Approach 1:
The patent applies phosphor materials locally on specific surfaces of the blue LED chip (top surface, side surfaces, or bottom surface) rather than uniformly throughout the entire device. This localized application achieves the desired light conversion while minimizing structural complexity and maintaining manufacturing simplicity
Solution Approach 2:
The patent uses a small, optimized amount of phosphor material (0.1-5% by weight) rather than large quantities. This partial action is sufficient to achieve the desired luminous flux enhancement without over-complicating the device structure or affecting the blue color appearance
3Illumination intensity
If green or yellow light is added to blue LED emission, then luminous flux increases due to eye sensitivity, but the color purity may be affected
Solution Approach 1:
The patent carefully controls the emission parameters of the phosphor materials (green: 500-545nm, yellow: 560-580nm) and their concentration (0.1-5% by weight) to optimize the balance between luminous flux enhancement and color accuracy. This parameter optimization ensures the combined light is perceived as blue while achieving peak luminous flux
Solution Approach 2:
The patent employs chromaticity coordinate control (x, y coordinates within specific ranges) as a feedback mechanism to monitor and adjust the phosphor concentration and distribution. This ensures the emitted light maintains the desired blue color appearance while maximizing luminous flux enhancement
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 approach results in significantly brighter blue light emitting devices with a luminous flux increase of up to 75% compared to conventional blue LEDs, while ensuring the light remains perceived as blue, by strategically using phosphor-converted blue LEDs with a thin recipient luminophoric medium.
Implementation Method 1
a recipient luminophoric medium that is configured to down-convert at least some of the blue light emitted by the blue LED. The recipient luminophoric medium includes luminescent materials that down-convert a portion of the blue light emitted by the blue LED to light having a peak wavelength that is between about 500 nanometers and about 545 nanometers
Data Source
AI summary
Light emitting devices include a blue LED that emits blue light having a peak wavelength between 430 nanometers and 480 nanometers and a recipient luminophoric medium that includes luminescent materials that down-convert a portion of the blue light emitted by the blue LED to light having a peak wavelength that is between about 500 nanometers and about 545 nanometers. The combination of the blue light emitted by the blue LED and the light emitted by the luminescent materials in the recipient luminophoric medium comprises light that is perceived as blue light having a color point that falls within the region on the 1931 CIE Chromaticity Diagram defined by ccx, ccy chromaticity coordinates of (0.1355, 0.0399), (0.175, 0.0985), (0.1743 0.1581), (0.1096, 0.0868), (0.1355, 0.0399).