Liquid Crystal Composition for Droplet Stain Reduction
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Solution Overview
Problem
Liquid crystal display devices face issues with droplet stains during manufacturing, particularly due to impurities and the use of unsuitable materials, which affect display quality and yield, and there is a need for a composition that reduces screen burn-in and maintains optimal properties like dielectric anisotropy and viscosity.
Innovation Solution
A liquid crystal composition containing specific compounds at predetermined mixing ratios, including those represented by Formulas (I-1) and (II), which are optimized to reduce droplet stains and screen burn-in while maintaining the necessary properties for liquid crystal display devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a compound having a dialkyl bicyclohexane skeleton is used to reduce γ1, then response speed is improved, but vapor pressure increases and Tni decreases
Solution Approach 1:
The patent modifies the molecular structure parameters of the bicyclohexane compound by introducing specific substituents (fluorine atoms at positions 2 and 6, and a nematicogenic group at position 4) to achieve optimal balance between response speed and stability. This structural parameter optimization allows the compound to exhibit low γ1 values while maintaining appropriate vapor pressure and Tni characteristics.
Solution Approach 2:
The patent creates a composite liquid crystal composition by combining the specifically designed bicyclohexane compound (Formula I) with other liquid crystal compounds (Formulae II and III). This composite approach allows the beneficial low γ1 property of the bicyclohexane compound to be utilized while the other components compensate for the unwanted high vapor pressure and low Tni, achieving overall composition stability.
2Reliability
If additives such as antioxidant and light absorber are added to liquid crystal composition, then stability is improved, but droplet stains are generated
Solution Approach 1:
The patent removes traditional additives (antioxidants and light absorbers) from the liquid crystal composition and instead achieves stability through the inherent chemical structure of the liquid crystal compounds themselves. The specifically designed compounds with fluorine substitution and nematicogenic groups provide intrinsic stability without requiring additional additives that would cause droplet stains.
Solution Approach 2:
The patent introduces a specific bicyclohexane compound with particular substituents as an intermediary that provides the stabilizing function previously achieved by additives. This compound acts as a mediator between the requirement for stability and the prohibition of droplet stain-causing additives, achieving both goals through its unique molecular structure.
3Productivity
If liquid crystal composition is dropped onto substrate for large-size displays, then manufacturing efficiency is improved, but droplet stains are generated
Solution Approach 1:
The patent converts the potential harm of droplet formation during dropping into a benefit by designing a composition with optimized surface tension and evaporation characteristics. The specific compound formulation ensures that any droplets formed during the dropping process evaporate cleanly without leaving stains, thus maintaining high manufacturing efficiency while eliminating the harmful droplet stain effect.
4Ease of operation
If acrylate-based monomer is used in PSA liquid crystal display devices, then pretilt angle control is improved, but ester bonds cause droplet stains
Solution Approach 1:
The patent uses a monomer component that is designed to be consumed during the polymerization process. The monomer with Formula (I-3) containing a polymerizable group is intentionally designed to be short-lived, converting into the polymer network that provides pretilt angle control without leaving residual ester bond-containing compounds that would cause droplet stains.
Data Source
Figure 1~3
Figure 4
AI summary
It is an object of the present invention to provide a liquid crystal composition which is suitably used in a liquid crystal display device without impairment of properties inherent in liquid crystal display devices, such as dielectric anisotropy, viscosity, upper limit of temperature of a nematic phase, stability of a nematic phase at low temperature, and γ1, and generation of screen burn-in in the display device, the liquid crystal composition being less likely to cause droplet stains in manufacturing of the liquid crystal display device and enabling ejection of a liquid crystal material in a stable amount in an ODF process; it is another object of the present invention to provide a liquid crystal display device in which such a liquid crystal composition is used. There is provided a liquid crystal composition having a negative dielectric anisotropy and containing a compound represented by Formula (I-1) and at least one compound represented by General Formula (II) and also provided a liquid crystal display device in which such a liquid crystal composition is used.