Liquid Crystal Medium with Polymerizable Compounds for Fast Switching
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Solution Overview
Problem
Current liquid crystal materials for VA and OCB displays have limitations such as long switching times, inability to generate pretilt angles, high threshold voltages, and reduced viewing angles, which affect the electro-optical properties and stability of the displays, especially at low temperatures.
Innovation Solution
A liquid-crystalline medium containing polymerizable compounds with specific structures, such as those with non-terminal alkenyl double bonds, is used to enhance the electro-optical properties by allowing for controlled pretilt angle setting, reducing rotational viscosity, and improving low-temperature stability, thereby shortening switching times and reducing threshold voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If conventional liquid crystal materials are used in VA and OCB displays, then the displays can operate, but the switching times are long and threshold voltages are high
Solution Approach 1:
The patent modifies the chemical structure of liquid crystal materials by introducing specific polymerizable compounds with non-terminal alkenyl double bonds. This changes the molecular parameters to reduce rotational viscosity and improve electro-optical properties, thereby reducing switching times and threshold voltages while maintaining stability
Solution Approach 2:
The patent creates a composite liquid crystal medium by combining conventional liquid crystal materials with specific polymerizable compounds. This composite approach leverages the beneficial properties of both components to achieve reduced switching times and improved electro-optical performance
2Productivity
If liquid crystal materials are used to achieve pretilt angles, then switching performance improves, but viewing angles are reduced
Solution Approach 1:
The patent optimizes the molecular structure and concentration of polymerizable compounds to control the pretilt angle generation. By carefully adjusting these parameters, the display achieves improved switching performance while maintaining wide viewing angles through optimized electro-optical properties
3Ease of operation
If liquid crystal materials are used for display applications, then electro-optical functions are achieved, but low-temperature stability is poor
Solution Approach 1:
The patent introduces polymerizable compounds with specific molecular structures that improve the phase behavior and thermal stability of the liquid crystal medium. This changes the physical parameters to enhance low-temperature stability while maintaining electro-optical functionality
Solution Approach 2:
The patent creates a composite liquid crystal system that combines materials with complementary properties, where the polymerizable compounds provide thermal stability and the conventional liquid crystal materials provide electro-optical functions, achieving both goals simultaneously
4Loss of time
If polymerizable compounds are added to liquid crystal media, then switching times are reduced, but UV exposure affects voltage holding ratio
Solution Approach 1:
The patent selects polymerizable compounds with specific structural characteristics that minimize UV-induced degradation. By optimizing the chemical parameters of the added compounds, the system achieves reduced switching times while maintaining voltage holding ratio stability after UV exposure
Solution Approach 2:
The patent exploits the polymerization capability of the added compounds to create a cross-linked network that actually improves UV resistance and voltage holding properties, converting the potential harmful effect of UV exposure into a beneficial stabilization mechanism
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 use of these polymerizable compounds in liquid-crystalline media results in displays with significantly reduced switching times, improved low-temperature performance, and enhanced electro-optical properties, including high specific resistances and wide viewing angles, while maintaining high clearing points and low voltage holding ratios even after UV exposure.
Implementation Method 1
the liquid crystal medium having a negative value of the DK anisotropy Δε. Due to the negative DK anisotropy, the liquid crystal molecules are reoriented parallel to the electrode surfaces when switched on
Implementation Method 2
The polymerizable compounds are polymerized in the display by photopolymerization, for example by UV irradiation
Implementation Method 3
displays based on DAP (deformation of erected phases), ECB (electrically controlled birefringence), VA (vertically aligned), CSH (color super homeotropic) or OCB (optically compensated bend) effect
Implementation Method 4
The molecules of this liquid crystal layer are oriented homeotropically or tilted when switched off
Data Source
AI summary
Liquid crystal medium (A) comprises one or more polymerizable compound and one or more phenyl-cyclohexane compound (I). Liquid crystal medium (A) comprises one or more polymerizable compound and one or more heterocyclic compound of formula (I). ring A : cyclohexane, phenyl or a substituted phenyl compound of formula (a); a : 0 or 1; L 1>, L 2>H, F (both preferred) or Cl; R 1>-(CH 2) m-CH=CH-C nH 2 n + 1; R 2>1-12C alkyl, where one or two non-adjacent CH 2-group is substituted by -O-, -CH=CH-, -CO-, -OCO- or -COO-, the O atoms are not connected directly, and terminal -CH=CH 2-groups are excluded; and either m : 0-6; or n+m : less than or equal to 6. Provided that when a is 0 then the ring A is cyclohexylene. Independent claims are included for: (1) an electro-optical display comprising (A) as a dielectric; and (2) the preparation of a medium comprising mixing (I), one or more polymerizable compound and optionally a further compound or additive. [Image].