Flexoelectric Liquid Crystal Window for Low-Power Privacy
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Solution Overview
Problem
Current liquid-crystal displays, such as TN and STN, require high power consumption and active-matrix addressing, and have significant viewing-angle dependence, whereas cholesteric liquid crystal (CLC) displays are bistable and have lower power consumption but lack polariser-free reflective displays with high contrast that are transparent in the off-state, which is essential for applications like privacy windows.
Innovation Solution
A window utilizing a flexoelectric liquid crystalline medium sandwiched between two substrates, one with an electrode structure, employing bimesogenic compounds that exhibit high elastic constant K11 and low bend elastic constant K33, allowing for two boundary states: a transparent state without an electric field and a light-scattering state with an applied field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If cholesteric liquid crystal (CLC) displays are used to achieve bistability and lower power consumption, then power consumption is reduced, but polariser-free reflective displays with high contrast that are transparent in the off-state cannot be achieved
Solution Approach 1:
The patent changes the fundamental parameters of the liquid crystal system by using bent-core nematic liquid crystals with converse flexoelectric effect instead of traditional cholesteric liquid crystals. This parameter change enables the system to achieve both low power consumption and transparency in the off-state by exploiting the unique flexoelectric properties of bent-core molecules, which allow for high-contrast reflective display without polarizers.
Solution Approach 2:
The patent employs a composite liquid crystal system comprising bent-core nematic liquid crystal molecules with specific molecular structures (containing mesogenic groups with flexible spacers) combined with chiral dopants to achieve the desired optical properties. This composite approach enables the material to exhibit both the bistability needed for low power consumption and the optical transparency required for the off-state.
2Ease of operation
If TN or STN displays are used to achieve liquid-crystal display functionality, then display operation is achieved, but high power consumption and active-matrix addressing are required
Solution Approach 1:
The patent implements self-service operation by utilizing the bistable nature of the flexoelectric liquid crystal system, where the liquid crystal molecules maintain their oriented state without continuous power supply. The system serves itself by retaining the displayed information in two stable states (transparent and light-scattering), eliminating the need for active-matrix addressing and continuous power consumption required by conventional TN or STN displays.
Solution Approach 2:
The patent employs periodic voltage pulses to switch between the two stable states of the liquid crystal system. Instead of continuous power application, brief periodic voltage pulses are used to transition the liquid crystal molecules between their stable configurations, significantly reducing power consumption while maintaining display functionality.
3Ease of operation
If conventional liquid crystal displays are used, then display functionality is achieved, but significant viewing-angle dependence occurs
Solution Approach 1:
The patent exploits phase transitions and structural transformations in the bent-core liquid crystal system, specifically the transition between different orientational states induced by the converse flexoelectric effect. This mechanism produces optical properties that are inherently less sensitive to viewing angle, as the light-scattering and reflective behaviors are determined by the molecular orientation transitions rather than traditional liquid crystal alignment layers that exhibit strong viewing-angle dependence.
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 window achieves efficient light transmission regulation with low power consumption and minimal viewing-angle dependence, maintaining the transparent state without an electric field and transitioning to a light-scattering state when needed, suitable for applications requiring transparency or blackout.
Implementation Method 1
liquid crystalline medium exhibiting a converse flexoelectric effect
Implementation Method 2
Devices utilizing the flexoelectric effect or corresponding mixtures are disclosed
Implementation Method 3
employing bimesogenic compounds that exhibit high elastic constant K11 and low bend elastic constant K33
Implementation Method 4
employing bimesogenic compounds that exhibit high elastic constant K11 and low bend elastic constant K33
Implementation Method 5
transitioning to a light-scattering state when needed
Data Source
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AI summary
The invention relates to a device for the regulation of light transmission, preferably a window, more preferably a privacy window, comprising a liquid crystalline medium exhibiting a converse flexoelectric effect, and which is sandwiched between two substrates, wherein at least one substrate is provided with an electrode structure.