Dual-Wavelength MQW White LED Backlight for Wide Color Gamut
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Solution Overview
Problem
Existing white LEDs used in LCD backlights lack suitable phosphors for narrowband green emission, limiting the color gamut of color LCD displays.
Innovation Solution
Employ Multiple Quantum Well (MQW) dual-wavelength LEDs that generate both narrowband blue and narrowband green light emissions, combined with manganese-activated fluoride phosphors to enhance color gamut, and utilize remote or packaged photoluminescence arrangements for optimal light conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If blue pumped photoluminescence wavelength converted white LEDs are used, then long operating life and high luminous efficacy are achieved, but color gamut is limited due to lack of suitable narrowband green emitting phosphors
Solution Approach 1:
The invention segments the white light generation function by using a dual-wavelength LED that emits both blue light (for phosphor conversion) and green light (direct emission). This separates the traditional single-function blue LED from the green light source, allowing independent optimization of each component's performance for its specific role.
Solution Approach 2:
The invention merges a blue LED and a green LED into a single integrated dual-wavelength LED chip. This combination allows the device to simultaneously provide both blue excitation light for phosphor conversion and direct green light emission, achieving high color gamut while maintaining the reliability benefits of LED technology.
2Ease of manufacture
If conventional white LEDs with broadband phosphors are used, then manufacturing simplicity is maintained, but color purity and color gamut are compromised
Solution Approach 1:
The invention applies local quality by using different phosphor materials with specific emission characteristics in different regions of the optical path. The blue LED excites red and yellow-green phosphors to create a localized spectral composition that, when combined with the direct green LED emission, achieves high color purity without complicating the overall manufacturing process.
3Adaptability or versatility
If narrowband red phosphors are used, then color gamut is improved, but suitable phosphors for narrowband green emission remain unavailable
Solution Approach 1:
Instead of relying on unavailable narrowband green phosphors, the invention uses a green LED that directly emits green light. This copies the function of what would be required from a green phosphor but achieves it through a different physical mechanism (electroluminescence from the green LED rather than photoluminescence from phosphor conversion).
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 color gamut that is at least 90% of the NTSC RGB color space standard, providing superior color quality in LCD displays.
Implementation Method 1
Photoluminescence wavelength converted white light emitting devices using LEDs, often referred to as 'white LEDs', typically comprise a blue LED and include one or more photoluminescence materials (typically inorganic phosphor materials), which absorb a portion of the blue light emitted by the LED and re-emit light of a different color (wavelength)
Data Source
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AI summary
A white light emitting device (backlight) comprises: a Multiple Quantum Well (MQW) dual -wavelength LED; and a narrowband photoluminescence material that generates red light with a peak emission wavelength from about 620 nm to about 660 nm. The MQW dual -wavelength LED comprises at least one first Quantum Well (QW) that generates blue light with a dominant wavelength from 440 nm to 470 nm and at least one second Quantum Well (QW) to generate green light with a dominant wavelength from 520 nm to 540 nm.