White Light Source Using Multi-Phosphor Layer for Natural Spectrum
Solution Overview
Problem
Conventional white light sources using LEDs have light emission spectra significantly different from natural light, which can adversely affect human circadian rhythms due to strong blue light emission peaks, disrupting the body's internal clock and leading to adverse health effects.
Innovation Solution
A white light source system that replicates the light emission spectrum of natural light by using a light emitting diode with a peak wavelength between 350 and 420 nm and a phosphor layer comprising four or more types of phosphors with different peak wavelengths, ensuring minimal chromaticity change and brightness degradation over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional white LEDs use blue LEDs with peak wavelength 400-530 nm and YAG phosphors, then white light is achieved with high luminous efficiency, but the blue light peak becomes too strong (at least 1.5 times the yellow light peak), causing adverse effects on human circadian rhythms
Solution Approach 1:
The patent segments the phosphor layer into four or more distinct phosphor types, each with different peak wavelengths. This segmentation allows control over the spectral distribution to reduce the blue light peak while maintaining overall luminous efficiency, thereby resolving the contradiction between efficiency and harmful blue light effects.
Solution Approach 2:
The patent uses a composite phosphor system combining four or more types of phosphors with different emission characteristics. This composite approach enables tuning of the overall light emission spectrum to achieve high luminous efficiency while suppressing the harmful blue light peak, resolving the technical contradiction.
2Stability of the object's composition
If four or more types of phosphors with different peak wavelengths are used, then the light emission spectrum closely matches natural light and chromaticity stability is improved, but the device complexity increases
Solution Approach 1:
The patent merges four or more types of phosphors into a single integrated phosphor layer that can be applied as one coating. This merging approach achieves stable chromaticity through the combined spectral properties of multiple phosphors while avoiding the complexity of multiple separate layers or components.
Solution Approach 2:
The phosphor layer serves multiple functions simultaneously: it converts blue LED light to other wavelengths, establishes a natural-like spectrum, and provides long-term chromaticity stability. This multi-functionality reduces the need for additional components, thereby managing device complexity while achieving the desired performance.
3Use of energy by moving object
If the phosphor layer contains high phosphor content for efficient light conversion, then luminous efficiency is improved, but brightness degradation accelerates over time due to phosphor aggregation and resin yellowing
Solution Approach 1:
The patent changes the parameter of phosphor particle size to an ultra-fine range (0.1-10 μm). This parameter change increases the surface area to volume ratio, improving light conversion efficiency while reducing phosphor aggregation. It also allows better dispersion in the resin, delaying yellowing and brightness degradation, thus resolving the contradiction between efficiency and reliability.
Solution Approach 2:
The patent applies different phosphor types with specific peak wavelengths (420-480 nm, 480-540 nm, 540-600 nm, 600-780 nm) to different regions of the spectrum. This local quality approach ensures efficient light conversion across all wavelengths while distributing the phosphor load, reducing aggregation effects and maintaining brightness stability over time.
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 system effectively suppresses adverse effects on human circadian rhythms by mimicking natural light, maintaining spectral similarity to black-body radiation, reducing chromaticity change, and preventing brightness degradation, thus providing a reliable and healthy lighting solution.
Implementation Method 1
a light emitting diode having a light emission peak wavelength in a range of 350 or more and 420 nm or less
Implementation Method 2
a phosphor layer including four or more types of phosphors and resin
Data Source
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AI summary
The present invention provides a white light source comprising: a light emitting diode (LED) having a light emission peak wavelength in a range of 350 or more and 420 nm or less; and a phosphor layer including four or more types of phosphors and resin, wherein the white light source satisfies a relational equation of: -0.2 ≤ [(P(λ) × V(λ)) / (P(λmax1) × V(λmax1)) - (B(λ) × V(λ)) / (B(λmax2) × V(λmax2))] ≤ +0.2, assuming that: a light emission spectrum of the white light source is P(λ); a light emission spectrum of black-body radiation having a same color temperature as that of the white light source is B(λ); a spectrum of a spectral luminous efficiency is V(λ); a wavelength at which P(λ) × V(λ) becomes largest is λmax1; and a wavelength at which B(λ) × V(λ) becomes largest is λmax2, and wherein an amount (difference) of chromaticity change on CIE chromaticity diagram from a time of initial lighting up of the white light source to a time after the white light source is continuously lighted up for 6000 hours is less than 0.010. According to the above white light source, there can be provided a white light source capable of reproducing the same light emission spectrum as that of natural light.