Cholesteric Liquid Crystal Composition for Bistable Privacy Dimming
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Solution Overview
Problem
Existing liquid crystal technologies face challenges in providing privacy protection in low-light environments and maintaining stable scattering states, with issues related to helical pitch affecting haze and stability, and requiring continuous power for mono-stable states.
Innovation Solution
A cholesteric liquid crystal composition with birefringence Δn ≥ 0.15 and helical pitch P ≤ 3.5 µm, incorporating a nematic liquid crystal, chiral compound, and elastic constant adjuster, to achieve bistable states with high haze and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the helical pitch is increased to improve the scattering effect, then the initial haze of the foggy state increases, but the stability of the foggy state weakens and haze reduces significantly over time
Solution Approach 1:
The patent optimizes the helical pitch parameter to a specific range (2-3.5 μm) to achieve the optimal balance between haze and stability. This parameter optimization ensures that the liquid crystal composition maintains high haze (≥80%) while preserving the stability of the foggy state over time, resolving the contradiction between initial haze performance and long-term stability.
2Illumination intensity
If the helical pitch is too large, then the scattering effect is enhanced, but domain structures become difficult to form and the stable scattering state is lost
Solution Approach 1:
The patent establishes an upper bound for the helical pitch parameter (P ≤ 3.5 μm) to ensure that domain structures can form properly. This parameter constraint guarantees that the liquid crystal composition maintains both the scattering effect and the reliability of the stable scattering state, preventing the loss of foggy state stability.
3Object-affected harmful factors
If PDLC is used to provide shielding effect for privacy, then the scattering state is achieved, but continuous power is required to maintain the state
Solution Approach 1:
The patent employs multi-stable liquid crystal materials that can maintain their scattering state without continuous external energy input. The material's inherent bistable or multistable characteristics allow it to remain in the foggy state after the electric field is removed, eliminating the need for continuous power consumption while maintaining privacy protection functionality.
4Object-affected harmful factors
If PDLC is used to provide shielding effect, then privacy protection is achieved, but the viewing angle is limited
Solution Approach 1:
The patent uses a composite liquid crystal composition combining nematic liquid crystal, chiral compound, and elastic constant adjuster to achieve both privacy protection and wide viewing angle. The synergistic effect of these components enables the material to maintain scattering properties from multiple viewing angles while providing effective privacy shielding.
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 composition maintains a stable foggy state with haze stability within 10% variation and low planar haze, enabling effective privacy protection and energy efficiency.
Implementation Method 1
the liquid crystal composition's birefringence Δn ≥ 0.15
Implementation Method 2
In the foggy state, liquid crystal molecules exist in a polydomain form, where molecules within a domain are mostly ordered, but disordered between domains, scattering incident light
Data Source
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AI summary
The present invention relates to a liquid crystal composition, the liquid crystal composition comprising at least one liquid crystal compound of a general formula (I), at least one elastic constant regulator of a general formula (II), and at least one chiral compound. The present invention also relates to a dimming device having at least two stable states, at least one state allowing incident light to pass through substantially (transmissive state), and at least one state scattering incident light substantially (haze state). The transmissive state and the haze state may be switched by means of an external electric field without the need for continuously maintaining a power connection. The transmissive state is clear and highly transmissive, while the haze state provides privacy shielding. The present invention, by means of introducing a bimesogenic compound, and adjusting the helical pitch P of the liquid crystal composition system such that P ≤ 3.5 µ m, improves the uniformity of a molecular plane arrangement of the liquid crystal composition and reduces texture defects, thereby lowering the haze of the dimming device containing the liquid crystal composition in the transmissive state, while increasing the haze thereof in the haze state. R3-MG1-Y1-X-Y2-MG2-R4 II