Nitride Semiconductor Light Source with Phosphor Conversion for Chromaticity Stability
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Solution Overview
Problem
Conventional light sources using nitride-based semiconductors for red, green, and blue light emission suffer from color shifts as temperature changes, affecting luminance and color purity, particularly in applications requiring stable chromaticity.
Innovation Solution
A light emitting device comprising a nitride-based semiconductor light emitting element with a peak emission wavelength between 370 nm and 420 nm, combined with a fluorescent material that converts this light to a peak emission wavelength between 550 nm and 780 nm, and additional nitride-based semiconductor light emitting devices for green and blue light, ensuring consistent color output across temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If nitride-based semiconductor light emitting elements are used for red, green, and blue light emission, then high luminance can be achieved, but color shifts occur as temperature changes affecting chromaticity stability
Solution Approach 1:
The patent changes the emission wavelength parameter of the blue light emitting element to 450 nm or more (specifically 460-480 nm range), which reduces the temperature coefficient of chromaticity shift. By selecting a specific wavelength parameter, the adverse temperature dependence is mitigated while maintaining high luminance output.
Solution Approach 2:
The patent uses a composite approach by combining multiple nitride-based semiconductor layers with different bandgaps to emit blue, green, and red light from a single device. This integrated structure allows coordinated optimization of all color emissions and their temperature characteristics, achieving high luminance while improving chromaticity stability across the visible spectrum.
2Illumination intensity
If conventional blue light emitting diodes with peak wavelength around 450 nm are used, then high blue light intensity is achieved, but significant chromaticity shift occurs with temperature changes
Solution Approach 1:
The patent shifts the blue light peak wavelength to 450 nm or more (optimally 460-480 nm), moving away from the conventional 450 nm peak. This parameter change reduces the temperature coefficient of the blue emission, thereby minimizing chromaticity shift with temperature while maintaining sufficient blue light intensity for effective green and red phosphor excitation.
3Stability of the object's composition
If multiple separate light emitting devices for red, green, and blue are used, then color purity can be maintained, but device complexity increases
Solution Approach 1:
The patent merges three separate light emitting functions (red, green, blue) into a single integrated nitride-based semiconductor device using multiple quantum well layers with different bandgaps. This consolidation maintains color purity through precise wavelength control while reducing device complexity by eliminating the need for separate devices and their associated mounting, wiring, and control circuits.
Solution Approach 2:
The nitride-based semiconductor device achieves multi-functionality by emitting blue light directly and simultaneously generating green and red light through phosphor conversion. A single device structure performs multiple functions (direct emission and phosphor excitation) that would traditionally require separate components, simplifying the overall system while maintaining color purity.
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 provides a light source with high luminance and color purity, minimizing chromaticity shifts even at varying temperatures, suitable for applications like displays and vehicle lighting.
Implementation Method 1
at least one fluorescent material to convert the first light to a second light having a second peak wavelength in a range of 550 nm or greater and to 780 nm or less
Data Source
AI summary
A light emitting device includes at least one first light emitting element to emit a first light having a first peak emission wavelength in a range of 370 nm or greater and 415 nm or less, and at least one fluorescent material to convert the first light to a second light having a second peak wavelength in a range of 550 nm or greater and to 780 nm or less. In an emission spectrum of the light emitting device, a ratio of an intensity of the first peak emission wavelength to a maximum intensity of the second peak emission wavelength is in a range of 0.005 to 0.20.