Photosensitive Chiral Agent Composition for Fast Cholesteric Color Switching
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Solution Overview
Problem
Existing cholesteric liquid crystal compositions face issues with insufficient reflectance retention ratio, slow UV-induced color switching, high viscosity, and slow switching speed, which affect the performance and cost-effectiveness of cholesteric liquid crystal displays.
Innovation Solution
A chiral agent compound with a cinnamate and isosorbide structure, featuring fluoroalkyl or fluoroalkoxy groups, is introduced to enhance helical twisting power (HTP), solubility, and switching speed, combined with a cholesteric liquid crystal composition that maintains high reflectance retention ratio and fast UV-induced color switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a photoresponsive chiral additive with high helical twisting power is used to achieve light-rewritable cholesteric liquid crystal display, then the pitch can be adjusted and reflected light colors can be changed, but the reflectance is insufficient and colorization is poor
Solution Approach 1:
The patent modifies the chemical structure of the chiral additive by introducing fluoroalkyl or fluoroalkenyloxy groups at specific positions of the cinnamate core structure. This structural parameter change increases the helical twisting power while maintaining good solubility, thereby improving both pitch adjustment capability and reflectance simultaneously
Solution Approach 2:
The patent creates a composite cholesteric liquid crystal system by combining the novel chiral additive (with specific molecular structure) with nematic liquid crystal hosts. This composite approach allows the system to achieve high reflectance through enhanced HTP while maintaining colorization capability through controlled pitch modulation
2Reliability
If a cholesteric liquid crystal composition is used to achieve high contrast and zero power consumption, then the displayed content can be maintained stably, but the reflectance retention ratio is poor and UV-induced color switching is slow
Solution Approach 1:
The patent changes the molecular parameters of the chiral additive by introducing fluorinated groups, which increases the helical twisting power. This parameter change accelerates the UV-induced color switching speed while the inherent stability of the cholesteric phase maintains the bistability required for low-power operation
Solution Approach 2:
The novel chiral additive acts as an intermediary that mediates between the UV light input and the cholesteric phase reconfiguration. Its enhanced HTP allows faster response to UV irradiation, reducing switching time while the cholesteric liquid crystal matrix maintains the stable planar and focal cone states for bistability
3Illumination intensity
If a relatively high refractive index is used to ensure high initial reflectance, then the reflectance is relatively high, but the reflectance drops significantly after UV-induced color switching
Solution Approach 1:
The patent modifies the chiral additive structure to achieve higher HTP, which allows the system to maintain stable chiral pitch even at lower refractive indices. This structural parameter change decouples the relationship between refractive index and reflectance retention, allowing high initial reflectance without significant drop after UV switching
4Illumination intensity
If an optically controlled chiral agent is used to achieve colorization in a single-layer liquid crystal cell, then the initial reflectance can be ensured, but the UV-induced color switching speed is slow and the process time is long
Solution Approach 1:
The patent changes the chemical structure of the chiral agent by introducing fluoroalkyl or fluoroalkenyloxy groups, which significantly increases the helical twisting power. This parameter change enables fast UV-induced color switching speed while maintaining good solubility and appropriate initial reflectance in a single-layer cell configuration
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 chiral agent compound achieves high HTP, good solubility, and short switching time, resulting in a cholesteric liquid crystal composition with improved reflectance retention and fast UV-induced color switching, suitable for active and passive matrix displays.
Implementation Method 1
The photoresponsive chiral additive may undergo a photo-induced molecular configuration change in a nematic liquid crystal, leading to a change in the helical twisting power
Implementation Method 2
The cholesteric liquid crystal has Bragg reflection when in the planar state. The reflection wavelength (λ) is determined by the average refractive index (n) and chiral pitch (P) of a liquid crystal composition, with λ=naverage×P
Implementation Method 3
The photoresponsive chiral additive may undergo a photo-induced molecular configuration change in a nematic liquid crystal, leading to a change in the helical twisting power and thus a change in the pitch (P) of the cholesteric liquid crystal
Data Source
AI summary
The present invention discloses photosensitive chiral agent compound S, a cholesteric liquid crystal composition containing the photosensitive chiral agent compound S, and the use of the cholesteric liquid crystal composition in a liquid crystal display element and a liquid crystal display. The photosensitive chiral agent compound S has the properties of high HTP value, good solubility, and short switching time. The cholesteric liquid crystal composition comprising the photosensitive chiral agent compound S has high reflectance retention ratio, which ensures RGB color uniformity and does not require complicated pixel design; low viscosity, which ensures compatibility with existing large-scale panel fabrication processes; and fast UV-induced color switching speed, which results in reduced time during the UV process and lowered production costs. The photosensitive chiral agent compound S can be widely used in optical devices such as liquid crystal electronic books and outdoor and vehicle-mounted displays.