Packaged LED with Shoulder Emission and Phosphor Optimization
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Solution Overview
Problem
Conventional semiconductor light emitting devices, such as LEDs, struggle to produce white light with high color rendering index (CRI) and luminous efficacy, especially when using blue LEDs with phosphor conversion, as they often lack sufficient red and green hues, leading to unnatural color representation of objects.
Innovation Solution
A packaged LED configuration that includes a blue LED with a peak wavelength less than 460 nm and a shoulder emission component at a longer wavelength, combined with a wavelength conversion material having specific color coordinates and a light-scattering lens, to produce warm white light with enhanced CRI and reduced red phosphor usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a blue LED chip is surrounded by a wavelength conversion material such as phosphor to generate white light, then white light is produced, but the color rendering is poor and objects are not illuminated well
Solution Approach 1:
The patent changes the particle size parameter of the yellow phosphor (increasing to 45-60 μm) and adjusts the wavelength conversion material composition to reduce red phosphor content while maintaining or improving color rendering. This parameter optimization allows achieving good color rendering with less red phosphor.
Solution Approach 2:
The patent uses a composite wavelength conversion material system comprising yellow phosphor (Y3Al5O12:Ce) and red phosphor (CaAlSiN3:Eu) in specific ratios, combined with a blue LED chip. This composite material approach optimizes the spectral output to achieve high CRI with reduced red phosphor content compared to conventional single-phosphor systems.
2Power
If conventional phosphor conversion methods are used with blue LEDs, then white light is generated, but the luminous efficacy and packaging factor are limited
Solution Approach 1:
The patent optimizes multiple parameters including yellow phosphor particle size (45-60 μm), phosphor layer thickness (20-50 μm), and wavelength conversion material composition ratios. These parameter changes improve light extraction efficiency and luminous efficacy while simplifying the packaging structure by reducing the need for complex multi-layer phosphor configurations.
Solution Approach 2:
The patent extracts and eliminates unnecessary packaging components and complex multi-phosphor layers by using a simplified two-phosphor system (yellow and red) with optimized particle sizes and ratios. This extraction of excess complexity improves manufacturing ease while maintaining high luminous efficacy.
3Illumination intensity
If more red phosphor is used to improve color rendering, then color representation improves, but the packaging factor and manufacturing complexity increase
Solution Approach 1:
The patent reduces red phosphor content to 5-20 wt% of total phosphor (down from conventional higher amounts) while increasing yellow phosphor particle size to 45-60 μm. This parameter change maintains CRI > 80 while significantly simplifying the manufacturing process and reducing packaging complexity.
Solution Approach 2:
The patent applies local quality optimization by using larger yellow phosphor particles (45-60 μm) in the dominant portion of the phosphor layer to handle the primary wavelength conversion, while using a minimal amount of red phosphor (5-20 wt%) only where needed to fill spectral gaps. This localized optimization achieves good color rendering without requiring uniform distribution of complex multi-phosphor compositions throughout the entire package.
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 a higher packaging factor, improved luminous efficacy, and more natural color representation of objects by generating warm white light with a high CRI, using less red phosphor and larger yellow phosphor particles, which enhances efficiency and reliability.
Implementation Method 1
a wavelength conversion material configured to receive the primary light emitted by the light emitting diode and to responsively emit light having a color point with a ccx greater than about 0.4 and a ccy less than about 0.6
Implementation Method 2
a light-scattering lens arranged over the wavelength conversion material and configured to refract light emitted by the LED and the wavelength conversion material, the light scattering lens may be configured to scatter the emitted light randomly
Data Source
AI summary
A packaged light emitting device (LED) includes a light emitting diode configured to emit primary light having a peak wavelength that is less than about 465 nm and having a shoulder emission component at a wavelength that is greater than the peak wavelength, and a wavelength conversion material configured to receive the primary light emitted by the light emitting diode and to responsively emit light having a color point with a ccx greater than about 0.4 and a ccy less than about 0.6.