Reflective LCD with Cholesteric Liquid Crystal and Quantum Dots
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Solution Overview
Problem
Current reflective liquid crystal display devices face issues with degraded visibility outdoors due to varying amounts of reflected light from external directions, and existing display technologies struggle to maintain excellent image quality both indoors and outdoors.
Innovation Solution
A reflective liquid crystal display device is designed with a cholesteric liquid crystal layer that selectively reflects blue light, combined with a light conversion member, such as quantum dots or rods, and a light absorbing layer to enhance color expression and visibility. The device includes a retardation member and a dichroic reflective layer to manage light wavelengths and absorption, ensuring consistent performance across different light angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a reflective display device is designed for outdoor use, then visibility in bright environments is improved, but the amount of reflected light varies depending on the direction of external light causing degraded visibility
Solution Approach 1:
The patent applies a cholesteric liquid crystal layer that selectively reflects specific wavelengths of light (blue, green, or red) based on its helical structure pitch. This wavelength-selective reflection property enables the display to maintain consistent color appearance and visibility across different viewing angles and external light directions, resolving the contradiction between outdoor visibility and visibility consistency.
Solution Approach 2:
The patent modifies the optical parameters of the liquid crystal layer by controlling the helical pitch to match specific wavelength ranges. By adjusting this physical parameter, the display achieves angle-independent reflection characteristics that maintain consistent visibility regardless of external light direction, while still providing excellent brightness for outdoor viewing.
2Manufacturing precision
If a cholesteric liquid crystal layer is used to selectively reflect light, then color expression is improved, but the reflected light amount varies with external light direction
Solution Approach 1:
The cholesteric liquid crystal layer is engineered with a specific helical pitch that corresponds to the wavelength range of the desired reflected color. This precise control of optical parameters enables accurate color expression while the inherent isotropic reflection property of the helical structure ensures consistent appearance from all viewing angles, eliminating the direction-dependent variability.
3Manufacturing precision
If quantum dots are used for light conversion, then color purity is improved, but the device complexity increases
Solution Approach 1:
The patent combines quantum dots with the cholesteric liquid crystal layer to create a composite optical system. The quantum dots provide narrow emission spectra for high color purity, while the cholesteric layer provides wavelength-selective reflection. This composite structure achieves superior color performance without requiring separate color filtering layers, thereby limiting the increase in device complexity.
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 improved color expression and consistent visibility outdoors by effectively managing light wavelengths and absorption, maintaining excellent image quality regardless of external light direction and intensity.
Implementation Method 1
the CLC layer may selectively reflect a first blue light having a wavelength range from about 400 nanometers (nm) to about 500 nm in a planar state
Implementation Method 2
the light conversion member may include a first light conversion member in a blue pixel area of the plurality of pixel areas, the first light conversion member excited by the first blue light to emit a second blue light, a second light conversion member in a green pixel area of the plurality of pixel areas, the second light conversion member excited by the first blue light to emit a second green light, and a third light conversion member in a red pixel area of the plurality of pixel areas, the third light conversion member excited by the first blue light to emit a second red light
Implementation Method 3
the light absorbing layer may absorb a visible light
Implementation Method 4
the retardation member may be a quarter wave retardation plate
Data Source
AI summary
A reflective liquid crystal display device includes a first substrate on which a plurality of pixel areas are defined, a second substrate facing the first substrate, a cholesteric liquid crystal (“CLC”) layer between the first substrate and the second substrate, a linear polarization member on the second substrate, a retardation member between the linear polarization member and the CLC layer, a light absorbing layer on the first substrate, and a light conversion member corresponding to the pixel area and interposed between the CLC layer and the light absorbing layer.