Cholesteric Liquid Crystal Wavelength Converter for LCD Color Gamut
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Solution Overview
Problem
Current LCD backlight modules using YAG phosphor LEDs result in an imbalance of blue, green, and red light, leading to a small color gamut and increased costs when using quantum dots to achieve color balance, as high amounts of quantum dots are required to maintain efficiency.
Innovation Solution
An enhanced wavelength converting structure incorporating a crosslinked cholesteric liquid crystal layer with dispersed quantum dots, which absorbs light and emits light of different wavelengths, reducing the need for excessive quantum dots by utilizing the microcavities mechanism and Bragg's law to adjust wavelength ranges and increase light intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a large amount of quantum dots is used to achieve color balance in large area LCD displays, then color gamut is improved, but manufacturing cost increases
Solution Approach 1:
The patent changes the physical and chemical parameters of the liquid crystal system by introducing a chiral dopant to create a cholesteric phase with specific pitch and optical properties. This enables the liquid crystal to interact with quantum dots more efficiently, allowing color balance to be achieved with reduced quantum dot concentration. The pitch of the cholesteric liquid crystal is tuned to match the emission wavelengths of quantum dots, enhancing energy transfer and reducing the required quantum dot amount.
Solution Approach 2:
The patent creates a composite material system combining liquid crystal, chiral dopant, and quantum dots in a synergistic configuration. The cholesteric liquid crystal phase acts as an intermediary that enhances the interaction between incident light and quantum dots, improving excitation efficiency. This composite approach allows for reduced quantum dot loading while maintaining or improving color balance and gamut coverage.
2Loss of energy
If scattering particles are added to the QD sheet to compensate for efficiency, then quantum efficiency is improved, but transmittance of the sheet is reduced
Solution Approach 1:
Instead of adding scattering particles, the patent changes the optical parameters of the liquid crystal medium itself by inducing a cholesteric phase. This phase provides selective reflection and enhanced light-matter interaction without the need for additional scattering centers. The pitch and helical structure of the cholesteric liquid crystal are optimized to enhance excitation of quantum dots while maintaining high transmittance in the visible range, avoiding the trade-off between efficiency and transmittance.
3Ease of manufacture
If YAG phosphor LEDs are used to produce white light, then manufacturing simplicity is maintained, but color gamut is reduced due to imbalanced RGB distribution
Solution Approach 1:
The patent introduces a cholesteric liquid crystal layer as an intermediary between the YAG phosphor LED backlight and the quantum dots. This intermediary layer enhances the excitation of quantum dots by the blue LED light through the microcavities mechanism and Bragg reflection, improving the conversion efficiency and color balance. The cholesteric liquid crystal acts as an optical mediator that amplifies the interaction between the backlight and quantum dots, enabling better color gamut with the same simple LED backlight structure.
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
This solution significantly reduces the amount of quantum dots needed while maintaining high quantum efficiency, enhancing color balance and luminance gain, and reducing optical loss through high film transparency.
Implementation Method 1
utilizing the microcavities mechanism and Bragg's law to adjust wavelength ranges and increase light intensity
Implementation Method 2
utilizing the microcavities mechanism and Bragg's law to adjust wavelength ranges and increase light intensity
Implementation Method 3
when a first light is incident into the enhanced wavelength converting structure, the plurality of first quantum dots are excited by the first light and emit a second light of a wavelength different from a wavelength of the first light
Data Source
AI summary
The present disclosure provides an enhanced wavelength converting structure. The enhanced wavelength converting structure includes a first crosslinked cholesteric liquid crystal layer and a plurality of first quantum dots dispersed in the first crosslinked cholesteric liquid crystal layer. When a first light is incident into the enhanced wavelength converting structure, the plurality of first quantum dots are excited and emit a second light of a wavelength different from a wavelength of the first light, and the second light is toned up via multiple reflections in the first crosslinked cholesteric liquid crystal layer. The present disclosure further provides a luminescent film and a display backlighting unit.