Nematic Liquid Crystal Composition for VA-Mode Displays
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Solution Overview
Problem
Developing a liquid crystal composition with negative dielectric anisotropy, low viscosity, and fast response for VA-mode liquid crystal display elements without compromising refractive index anisotropy or nematic-isotropic liquid phase transition temperature, while minimizing display defects and achieving high elastic constants and voltage holding ratios.
Innovation Solution
A specific combination of compounds with difluorobenzene skeletons and other selected compounds, including those represented by general formulae (I), (IV-1) to (IV-3), and (N3), optimized for content and structure to achieve the desired properties, is used in the liquid crystal composition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If compounds (C) and (D) are used to achieve negative Δε, then dielectric anisotropy is improved, but viscosity is not sufficiently low for fast response
Solution Approach 1:
The patent modifies the molecular structure parameters by introducing specific fluorine atom positions (2,3-difluorophenylene skeleton) and side chain configurations to achieve optimal balance between dielectric anisotropy and viscosity. This structural parameter optimization allows the liquid crystal composition to simultaneously attain sufficiently negative Δε and low viscosity for fast response.
Solution Approach 2:
The patent creates a composite liquid crystal composition by combining compound (A) with compounds (C) and (D) in specific ratios. This composite approach leverages the complementary properties of each compound: compound (A) provides the necessary dielectric anisotropy through its fluorinated phenylene structure, while the combination with compounds (C) and (D) achieves the desired viscosity reduction for fast response characteristics.
2Speed
If alkenyl compounds are added to improve response speed, then viscosity is reduced, but display defects such as image persistence and display unevenness occur
Solution Approach 1:
The patent optimizes the alkenyl group configuration within compound (A) by specifying particular carbon chain lengths and double bond positions. This controlled modification of molecular parameters enables the achievement of low viscosity for fast response while maintaining display quality by preventing excessive alkenyl compound effects that cause image persistence and display unevenness.
Solution Approach 2:
The patent introduces fluorine atoms at specific positions (2,3-difluorophenylene) within the molecular structure to create localized regions with optimized electronic and steric properties. This local structural optimization allows the molecule to contribute to low viscosity and fast response while the overall molecular architecture prevents display defects, achieving both fast response and high display quality.
3Reliability
If refractive index anisotropy Δn is increased, then display quality is improved, but viscosity increases causing slow response
Solution Approach 1:
The patent optimizes the balance between refractive index anisotropy and viscosity by carefully designing the molecular structure of compound (A) with specific fluorine substitutions and side chain configurations. This parameter optimization ensures that Δn remains within the appropriate range for high display quality while the molecular geometry and fluorine effects maintain low viscosity for fast response, resolving the trade-off between these two critical parameters.
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 achieves low viscosity, low rotational viscosity, large elastic constants, and high voltage holding ratios, ensuring fast response and minimal display defects with excellent display quality, particularly suitable for VA-mode liquid crystal display elements with small cell gaps.
Implementation Method 1
the liquid crystal composition having negative dielectric anisotropy (Δε)
Implementation Method 2
VA-mode liquid crystal display element having no or minimal display defects and having excellent display quality and a fast response
Implementation Method 3
In view of the setting of Δn × d, which is the product of refractive index anisotropy (Δn) and a cell gap (d), Δn of a liquid crystal material needs to be adjusted within an appropriate range
Implementation Method 4
a liquid crystal material having low viscosity (η) is required
Data Source
AI summary
The present invention relates to a nematic liquid crystal composition useful as a liquid crystal display material, the liquid crystal composition having negative dielectric anisotropy (Δε), and to a liquid crystal device element including the liquid crystal composition. The liquid crystal composition of the present invention has sufficiently low viscosity (η), sufficiently low rotational viscosity (γ1), a large elastic constant (K33), and a negative dielectric anisotropy (Δε) whose absolute value is large, without reducing the refractive index anisotropy (Δn) or the nematic-isotropic liquid phase transition temperature (Tni). Provided is, for example, a VA-mode liquid crystal display element including the liquid crystal composition, the liquid crystal display element having no or minimal display defects and having excellent display quality and a fast response. The liquid crystal display element including the liquid crystal composition of the present invention is useful for an active matrix-addressed liquid crystal display element and used for, for example, a VA- or PSVA-mode liquid crystal display element.