Nitride Phosphor Blend for White LED Color Rendering
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Solution Overview
Problem
Conventional white LED backlights using a blue LED and yellow phosphor suffer from quantum deficits and re-radiation efficiency issues, leading to degraded brightness and unnatural color representation, lacking green and red components, which limits their application.
Innovation Solution
A light emitting device incorporating a combination of green, yellow, and red nitride phosphors with specific compositional ratios, where the phosphors absorb blue or ultraviolet light to emit a wide spectrum of colors, including green, yellow, and red, enhancing color reproducibility and brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a blue LED and yellow phosphor combination is used, then the device is easily driven and economical, but the color rendering is unnatural and green and red components are lacking
Solution Approach 1:
The patent uses a composite phosphor system combining yellow phosphor (Y3Al5O12:Ce) with green phosphor (β-SiAlON:Eu) and red phosphor (CaAlSiN3:Eu) to create a multi-component material system that emits a broader spectrum covering green and red wavelengths, thereby improving color rendering while maintaining LED compatibility
Solution Approach 2:
The patent optimizes the compositional ratios of the phosphors, specifically setting the yellow phosphor content at 70-90 wt%, green phosphor at 5-20 wt%, and red phosphor at 5-20 wt%, along with controlling the particle size distribution (D50 values) to achieve optimal color rendering and luminous efficiency
2Illumination intensity
If secondary light source with phosphor is used, then white light is emitted, but quantum deficits and re-radiation efficiency are degraded
Solution Approach 1:
The patent selects phosphor materials with specific properties including narrow FWHM (full width at half maximum) values to reduce spectral overlap and quantum deficits, and optimizes the peak wavelengths to match the blue LED emission spectrum, thereby improving energy transfer efficiency and reducing re-radiation losses
3Ease of manufacture
If silicate phosphor is used, then the phosphor can be used for backlight unit, but the reliability is inferior due to weakness to moisture
Solution Approach 1:
The patent replaces moisture-sensitive silicate phosphor with nitride-based phosphors (β-SiAlON:Eu and CaAlSiN3:Eu) that possess superior chemical stability and moisture resistance, while maintaining the desired green and red emission properties, thereby improving device reliability without sacrificing manufacturability
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 device achieves improved color rendering index, wider standard color space coverage, and increased luminous intensity with a flat section in the emission spectrum, addressing the limitations of conventional white LED backlights.
Implementation Method 1
a phosphor, which is pumped by a pumping light source having high energy such as ultraviolet light or blue light to emit visible light
Data Source
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AI summary
Disclosed are a phosphor and a light emitting device having the same. The light emitting device includes a light emitting chip, a plurality of phosphors to absorb a portion of light emitted from the light emitting chip and to emit lights having mutually different peak wavelengths, and a molding member provided on the light emitting chip and including the phosphors. The phosphors include a first phosphor to emit light having a first peak wavelength, a second phosphor to absorb the portion of the light emitted from the light emitting chip and to emit light having a second peak wavelength, and a third phosphor to absorb the portion of the light emitted from the light emitting chip and to emit light having a third peak wavelength. The first to third peak wavelengths have mutually different color spectrums, and a light emission spectrum in which the first to third peak wavelengths are mixed with each other has a luminous intensity having a flat section in at least 30 nm at a peak wavelength thereof.