Reflective LCD Composite System via Spatially Selective Polymerisation
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Solution Overview
Problem
Reflective liquid crystal displays face challenges in achieving favorable contrast, mechanical stability, and efficient electro-optical performance, particularly in terms of low power consumption and reduced temperature dependence of reflection wavelength, while maintaining high birefringence and dielectric anisotropy.
Innovation Solution
A liquid-crystalline medium comprising mesogenic compounds, chiral compounds, and polymerizable compounds with specific structural features, where the polymerizable compounds are polymerized in a spatially selective manner to form a composite system with distinct polymeric and low molecular weight phases, enhancing mechanical stability and electro-optical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a cholesteric liquid crystal medium is used for reflective display operation, then selective light reflection and color display are achieved, but unwanted light reflection in inactive areas and poor contrast occur
Solution Approach 1:
The display surface is divided into active and inactive areas through spatially selective polymerisation. Polymer walls are formed only in inactive areas to suppress unwanted light reflection, while active areas remain free of polymer structures to maintain selective light reflection and color display functionality.
Solution Approach 2:
Different regions of the display are given different properties: inactive areas receive polymer walls for light absorption and reflection suppression, while active areas maintain their cholesteric liquid crystal structure for selective light reflection and color display.
2Stability of the object's composition
If polymerisable compounds are added to the liquid crystal medium, then mechanical stability is improved, but phase separation and reduced homogeneity occur
Solution Approach 1:
The liquid crystal medium is prepared with polymerisable compounds mixed homogeneously before the display is operated. Spatially selective polymerisation is then performed to form polymer walls in inactive areas, providing mechanical stability while avoiding phase separation through controlled local polymerisation.
3Reliability
If high birefringence and dielectric anisotropy are achieved, then electro-optical performance is improved, but temperature dependence of reflection wavelength increases
Solution Approach 1:
The liquid crystal medium is formulated with specific mesogenic compounds and chiral dopants to achieve high birefringence and dielectric anisotropy for improved electro-optical performance. The pitch of the cholesteric helix is carefully controlled to compensate for temperature dependence, maintaining stable reflection wavelength across a wide temperature range.
4Use of energy by moving object
If reflective mode operation is implemented, then power consumption is reduced, but contrast and image quality deteriorate
Solution Approach 1:
Polymer walls are introduced as an intermediary structure in inactive areas to suppress unwanted light reflection. This mediator absorbs or scatters stray light, thereby improving contrast and image quality while maintaining the low power consumption benefits of reflective mode operation.
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 reflective liquid crystal displays with improved contrast, mechanical stability, and reduced power consumption, along with stable electro-optical performance across a wide temperature range, while minimizing unwanted light reflection in inactive areas.
Implementation Method 1
The one or more polymerisable compounds are polymerised in a spatially selective manner to form a composite system
Implementation Method 2
A liquid-crystalline medium comprising mesogenic compounds, chiral compounds, and polymerizable compounds... provides reflective liquid crystal displays with improved contrast
Implementation Method 3
one or more mesogenic compounds selected from the group of compounds of formulae I and II... one or more chiral compounds
Implementation Method 4
maintaining high birefringence and dielectric anisotropy
Implementation Method 5
maintaining high birefringence and dielectric anisotropy
Data Source
AI summary
The present invention relates toaliquid crystalline medium which comprisesone or more mesogenic compounds selected from the group of compounds of formulae I and II as set forth in claim 1, one or morechiral compoundsand one or more polymerisable compounds, to a composite system obtained fromor respectively obtainable fromthe medium by polymerising the one or more polymerisable compounds, andto liquid crystal displays comprising thecomposite system,in particulardisplays operating in reflective mode. The present invention further relates toa process for preparing the composite system comprisingspatially selective polymerisation.