Amber Light Emitting Device with Band-Pass Filter
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Solution Overview
Problem
Light emitting devices equipped with LEDs and fluorescent materials often fail to maintain an amber color tone when used in conjunction with red filters, due to the large full width at half maximum of their light emission spectra, leading to visual recognition as red rather than amber.
Innovation Solution
A light emitting device comprising a light emitting element with a peak wavelength between 380 nm and 470 nm, a fluorescent material layer with a peak wavelength between 500 nm and 780 nm, and a band-pass filter layer that transmits light between 560 nm and 630 nm, ensuring an average reflectance of 90% or more for light within specific wavelength ranges and a narrow full width at half maximum to maintain the amber color tone even when a red filter is applied.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a light emitting device uses a fluorescent material with a broad emission spectrum to achieve high brightness, then the brightness is improved, but the color purity deteriorates and the light cannot be visually recognized as amber when passed through a red filter
Solution Approach 1:
The patent segments the wavelength conversion function into multiple fluorescent materials with different emission characteristics. Specifically, it uses a first fluorescent material (yellow emission) and a second fluorescent material (red emission) separately, rather than relying on a single broad-spectrum material. This segmentation allows precise control over the spectral composition to achieve amber color after red filter transmission.
Solution Approach 2:
The patent employs a composite wavelength conversion layer containing multiple fluorescent materials (yellow-emitting and red-emitting materials) in specific combinations. This composite structure enables the device to produce a tailored emission spectrum that maintains amber color purity after passing through a red filter, while preserving high brightness through synergistic contribution of multiple materials.
2Power
If the full width at half maximum of the light emission spectrum is widened to increase luminous output, then the luminous output is improved, but the color tone recognition deteriorates and amber color cannot be distinguished from red
Solution Approach 1:
The patent applies local quality by assigning specific emission characteristics to different regions of the spectrum. The first fluorescent material targets the yellow region (580-600nm) while the second fluorescent material targets the red region (610-650nm). This localized spectral engineering ensures that the combined emission maintains the amber color tone (yellowish-red) required for visual recognition, even with high luminous output.
Solution Approach 2:
The patent changes the spectral parameters by selecting fluorescent materials with specific emission peak wavelengths and narrow full widths at half maximum. The yellow-emitting material has a peak at 580-600nm with FWHM of 80-120nm, and the red-emitting material has a peak at 610-650nm with FWHM of 50-100nm. These controlled parameter changes enable high luminous output while maintaining distinct amber color recognition after red filter transmission.
3Adaptability or versatility
If a red filter is added to the light emitting device to adjust the color output, then the color adjustment capability is improved, but the amber color tone is lost and the light appears red instead
Solution Approach 1:
The patent applies preliminary action by pre-configuring the wavelength conversion layer with specific fluorescent materials whose emission spectra are optimized for amber color production. The yellow-emitting and red-emitting materials are selected and positioned to ensure that their combined emission, when passed through a red filter, maintains the amber color tone. This preliminary spectral engineering eliminates the need for post-filter color correction.
Solution Approach 2:
The patent introduces the wavelength conversion layer with specific fluorescent materials as an intermediary between the blue LED excitation source and the red filter. This intermediary layer converts the blue light (430-470nm) into yellow and red emissions, creating an amber-colored intermediate spectrum that can successfully pass through the red filter while maintaining amber color recognition, rather than producing pure red light.
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 emits light with a chromaticity coordinate within the target amber region of the CIE 1931 chromaticity diagram, retaining the amber color tone after transmission through a red filter, with improved color purity and reduced color tone conversion.
Implementation Method 1
a light emitting element having a light emission peak wavelength in a range of 380 nm or more and 470 nm or less
Implementation Method 2
a fluorescent material layer containing a fluorescent material excited by light emitted from the light emitting device
Implementation Method 3
The band-pass filter layer transmits light in a wavelength range of 560 nm or more and 630 nm or less
Implementation Method 4
has an average reflectance to the light in a wavelength range of 380 nm or more and less than 560 nm of 90% or more, and an average reflectance to the light in a wavelength range of more than 630 nm and 780 nm or less of 90% or more
Data Source
AI summary
A light emitting device includes: a light emitting element having a light emission peak wavelength in a range of 380 nm or more and 470 nm or less, and a wavelength conversion member disposed on a light emission side of the light emitting device and comprising: a fluorescent material layer containing a fluorescent material excited by light emitted from the light emitting device, having a light emission peak wavelength in a range of 500 nm or more and 780 nm or less, and a band-pass filter layer disposed on a light emission side of the fluorescent material layer.