PNLC Light Modulation Element with Cholesteric LC Medium
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current liquid crystal display technologies face challenges in achieving high haze values while maintaining fast switching times and low voltages, particularly in cholesteric liquid crystal (LC) cells with a helical pitch in the micron range, which affects their infrared reflection band and color neutrality.
Innovation Solution
A cholesteric LC medium comprising polymerizable compounds, non-polymerizable mesogenic compounds, and chiral compounds, where the polymerizable compounds are polymerized to form a polymer network within the LC cell, optimizing the helical pitch for infrared reflection and enhancing switching properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the helical pitch is increased to the micron range for infrared reflection, then the reflection band shifts to infrared spectrum eliminating color effects, but the switching off time increases making it unsuitable for display applications
Solution Approach 1:
The patent uses a composite system combining cholesteric liquid crystal with a polymer network (PNLC). The polymer matrix provides structural support and controls the helical pitch at micron scale for infrared reflection, while the liquid crystal phase maintains fast switching capability. This composite approach allows simultaneous achievement of infrared reflection (via micron-scale pitch) and fast switching (via LC molecular reorientation).
Solution Approach 2:
The patent optimizes multiple parameters including helical pitch (micron range), polymer network density, and liquid crystal composition to achieve the desired balance. By carefully controlling the pitch parameter in the micron range and adjusting the polymer-liquid crystal ratio, the system achieves infrared reflection while maintaining acceptable switching speeds through parameter optimization.
2Reliability
If polymer network systems are used for dynamic scattering, then moderate haze values of 44% are achieved, but high haze values required for display applications are not reached
Solution Approach 1:
The patent systematically varies the polymer network density, crosslinking degree, and liquid crystal composition to optimize haze values. By adjusting parameters such as polymer concentration, photopolymerization conditions, and chiral dopant content, the system achieves haze values suitable for display applications while maintaining fast switching characteristics.
3Temperature
If cholesteric liquid crystal cells with micron-range helical pitch are used, then infrared reflection and color neutrality are achieved, but fast switching and low voltage requirements cannot be simultaneously maintained
Solution Approach 1:
The PNLC composite structure allows the polymer matrix to maintain the micron-scale helical pitch for infrared reflection while the liquid crystal molecules provide fast reorientation response. The polymer network acts as a scaffold that preserves the cholesteric structure without restricting the rapid molecular switching needed for fast response times and low operating voltages.
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 enables high haze values, fast switching times, and low voltage requirements, suitable for display applications, while maintaining color neutrality and efficient infrared light modulation.
Implementation Method 1
the polymerisable compounds are polymerised
Implementation Method 2
When an LC cell is edge-lit, the light can experience total internal reflection within the boundaries of the LC cell
Implementation Method 3
When a chiral liquid crystal cell is switched, focal conic domains are formed and this large change in apparent refractive index leads to haze and subsequently light outcoupling from the LC cell
Data Source
AI summary
The present invention relates to a cholesteric liquid crystalline (LC) medium for a Polymer-Network Liquid Crystalline (PNLC) light modulation element, to a method of its production and to the use of such cholesteric LC media in PNLC light modulation elements. Furthermore, the present invention relates to PNLC light modulation elements, as such, to a method of their production, to the use of such light modulation elements in optic or electro optic devices, in particular in LC displays, and to optic or electro optic devices comprising such light modulation elements according to the present invention.