Polymerizable Liquid Crystal Compound for Vertical Alignment
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Solution Overview
Problem
Liquid crystal media used in active matrix addressing modes, such as VA mode, face issues like afterimage, slow response time, high drive voltage, and uneven display due to uneven electrode widths, which are not adequately addressed by current technologies, and the PI application process is costly and polluting.
Innovation Solution
A compound represented by formula I with specific structural features that allows self-alignment and polymerization upon UV exposure, forming a polymer layer for stable pre-tilt angles and vertical alignment, reducing the need for PI and improving display performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional PI application process is used for vertical alignment, then alignment function is achieved, but manufacturing cost increases and organic pollutants are emitted
Solution Approach 1:
The invention extracts and eliminates the need for the separate PI application process by incorporating alignment functionality directly into the liquid crystal composition through polymerizable mesogenic units. The liquid crystal mixture itself performs the alignment function after UV irradiation, removing the harmful PI coating step entirely while maintaining vertical alignment capability.
Solution Approach 2:
The liquid crystal composition is designed to perform multiple functions: it provides both the liquid crystal display functionality and the vertical alignment function simultaneously. The polymerizable mesogenic units enable the liquid crystal mixture to self-align vertically upon UV irradiation, combining what were previously separate functions (liquid crystal operation and alignment layer provision) into a single multi-functional material system.
2Reliability
If polymerizable mesogenic units are added to liquid crystal composition, then self-alignment function is achieved and PI process is simplified, but solubility and stability challenges arise
Solution Approach 1:
The invention carefully controls the concentration of polymerizable mesogenic units within a specific range (0.1-10 wt%) to optimize both solubility and alignment functionality. By adjusting this parameter, the composition maintains homogeneous mixing before UV irradiation while ensuring sufficient polymerization capability after irradiation to achieve stable vertical alignment.
Solution Approach 2:
The liquid crystal composition is designed as a composite system combining liquid crystal molecules with polymerizable mesogenic units. This composite structure allows the liquid crystal phase to maintain its flow and alignment properties while the polymerizable units provide the capability for post-irradiation network formation, achieving both solubility during operation and stability after polymerization.
3Reliability
If VA mode liquid crystal media are used, then display function is achieved, but afterimage level is significantly worse and response time is slow
Solution Approach 1:
The invention modifies the liquid crystal composition parameters by incorporating polymerizable mesogenic units and controlling the mixture composition, which changes the molecular packing and interaction characteristics. This leads to improved response characteristics while maintaining the vertical alignment mode display function, addressing both the afterimage and response time issues simultaneously.
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 compound enhances solubility, response speed, and stability, providing a wider nematic phase temperature range, high electrical resistivity, and anti-ultraviolet properties, while simplifying the panel production process and avoiding the costs and pollution of traditional PI application.
Implementation Method 1
the compound easily absorbs UV and rapidly polymerizes, such that a polymer having an alignment function may be formed
Data Source
AI summary
A compound represented by formula I, a negative liquid crystal composition comprising such a compound, and a liquid crystal display element or liquid crystal display comprising the compound or liquid crystal composition are provided. The compound represented by formula I contains two hydroxy groups. In an ODF process for a panel, due to an intermolecular force between the hydroxyl groups and the surface of the panel (a glass surface or an ITO electrode surface), the compound is spontaneously aligned, in a standing manner, on the panel glass or transparent ITO electrode substrate, causing liquid crystal molecules similar to the compound represented by formula ITO be vertically aligned, and UV light irradiation, a polymer layer with a rough surface is formed on the substrate by means of polymerization, and achieves the effects of PI insulation and vertical alignment of the liquid crystal molecules.