Liquid Crystal Medium with Methacrylate Compounds for Fast Switching
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Solution Overview
Problem
Current liquid crystal displays, particularly VA and OCB types, face challenges with high rotational viscosity, inadequate voltage holding ratio, and long switching times, especially at low temperatures, due to unsuitable combinations of liquid crystal mixtures and polymerizable compounds, which limit their performance in terms of contrast, viewing angle, and luminance.
Innovation Solution
The use of liquid crystal media containing polymerizable compounds with methacrylate groups and low molecular weight alkenyl compounds, which stabilize under polymerization conditions, enabling improved tilt values and voltage holding ratios, and reducing rotational viscosity for faster switching times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional liquid crystal mixtures are used in VA displays, then viewing angle is improved, but rotational viscosity increases and switching times lengthen
Solution Approach 1:
The patent modifies the chemical composition parameters of the liquid crystal mixture by incorporating specific compounds (cylohexyl compounds with formula I, compounds of formula II, and compounds of formula III) in defined concentration ranges. This chemical parameter change optimizes the balance between viewing angle and switching speed by altering the molecular properties of the liquid crystal medium.
Solution Approach 2:
The patent creates a composite liquid crystal medium by combining multiple specific compounds (cylohexyl compounds, compounds of formula II, and compounds of formula III) in a defined mixture. This composite approach allows the material to exhibit synergistic properties that simultaneously provide wide viewing angle and fast switching response, overcoming the limitations of single-component systems.
2Reliability
If polymerizable compounds are added to liquid crystal media, then voltage holding ratio is improved, but rotational viscosity increases
Solution Approach 1:
The patent carefully controls the concentration parameter of polymerizable compounds within specific ranges (0.1-5 wt%, preferably 0.5-3 wt%) to optimize the voltage holding ratio while minimizing the negative impact on rotational viscosity. This parameter optimization ensures that the polymerization process enhances electrostatic retention without excessively increasing material viscosity.
Solution Approach 2:
The patent introduces polymerizable compounds selectively into specific regions of the liquid crystal medium where they can undergo localized polymerization. This local quality approach allows the polymerization to occur primarily in the bulk material to enhance voltage holding, while minimizing the formation of large polymer aggregates that would increase rotational viscosity and slow switching.
3Speed
If alkenyl compounds are used in liquid crystal mixtures, then switching time is reduced, but voltage holding ratio deteriorates
Solution Approach 1:
The patent creates a composite liquid crystal system by combining alkenyl-containing compounds (formula I and II) with specific cylohexyl compounds (formula III) that have different molecular properties. This composite approach allows the alkenyl compounds to provide fast switching through their low rotational viscosity, while the cylohexyl compounds compensate by improving voltage holding ratio through their electrostatic properties.
Solution Approach 2:
The patent optimizes the concentration parameters of alkenyl compounds (formula I and II) within specific ranges to achieve the desired balance. By controlling the amount of alkenyl compounds present, the system achieves sufficient reduction in rotational viscosity for fast switching while maintaining adequate voltage holding ratio through the complementary presence of cylohexyl compounds.
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
This combination results in liquid crystal displays with enhanced voltage holding ratios, reduced switching times, and improved contrast and luminance, particularly suitable for TFT PSA VA displays, with stable performance across a wide temperature range.
Implementation Method 1
The liquid crystal medium contains one or more polymerizable compounds, with all polymerizable compounds present in the liquid crystal medium having exclusively methacrylate groups as polymerizable groups
Implementation Method 2
the FK medium typically has a negative value of dielectric (DK) anisotropy. When switched off, the molecules of the FK layer are oriented perpendicular to the electrode surfaces (homeotropic) or tilted homeotropically. When an electrical voltage is applied to the electrodes, the FK molecules are reoriented parallel to the electrode surfaces.
Implementation Method 3
OCB displays (optically compensated bend) are known, which are based on a birefringence effect and have an FK layer with a so-called 'bend' orientation and usually positive (DK) anisotropy
Data Source
AI summary
Liquid crystal medium (Q) comprises one or more polymerizable compounds, where the polymerizable compounds have polymerizable groups excluding methacrylate groups; and one or more low molecular mesogenic or liquid crystalline compounds with one or more alkenyl group, which: are stable against polymerization reaction and used under the conditions in relation to the polymerization of the methacrylate group. Independent claims are included for: (1) a liquid crystal display comprising liquid crystal cell containing two substrates, where at least a substrate is light permeable and at least another substrate is electrode layer, and a layer between the substrates of (Q), where the polymerizable component is obtained by polymerizing one or more polymerizable compounds between the substrates of the liquid crystal cell in (Q) under electrical voltage; and (2) the preparation of (Q), comprising mixing one or more low molecular liquid crystal compounds with one or more polymerizable compounds, and optionally with further liquid crystal compounds and/or additives.