Polymerizable Compound for Vertical Alignment in Liquid Crystal Displays
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Solution Overview
Problem
Existing VA mode liquid crystal displays using polyimide alignment films are costly, and self-aligning additives fail to provide sufficient electro-optical characteristics and alignment uniformity, necessitating a more effective method for aligning liquid crystal molecules without PI layers.
Innovation Solution
A polar-group-containing polymerizable compound represented by general formula (i) is used in a liquid crystal composition to achieve vertical alignment of liquid crystal molecules, eliminating the need for polyimide layers by incorporating a polymerizable group and specific structural portions that enhance alignment and storage stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyimide alignment layers are used to achieve vertical alignment of liquid crystal molecules, then alignment performance is improved, but production cost increases significantly
Solution Approach 1:
The patent extracts and eliminates the polyimide alignment layer from the display structure by developing a liquid crystal composition with self-aligning capabilities. The composition contains specific compounds (e.g., hydroxy-group-containing compounds or carboxyl-group-containing compounds) that enable the liquid crystal molecules to align vertically on their own without requiring the expensive PI layer, thus removing the harmful factor (high cost) while maintaining the useful function (alignment performance).
Solution Approach 2:
The patent introduces a mediator substance (self-aligning additive with specific chemical groups) into the liquid crystal composition. This mediator enables the liquid crystal molecules to achieve vertical alignment through molecular interactions with the substrate, replacing the function previously performed by the polyimide alignment layer. The mediator compound acts as an intermediary that transfers the alignment function from the alignment layer to the liquid crystal composition itself.
2Ease of manufacture
If self-aligning additives are used to eliminate polyimide layers, then production cost is reduced, but electro-optical characteristics and alignment uniformity deteriorate
Solution Approach 1:
The patent systematically changes the chemical parameters of the self-aligning additives by specifying precise structural requirements: compounds must contain specific functional groups (hydroxy, carboxyl, or their derivatives) with defined chemical structures and purity ranges. By optimizing these chemical parameters within specified ranges, the patent achieves both cost reduction and maintains excellent electro-optical characteristics and alignment uniformity.
Solution Approach 2:
The patent creates a composite liquid crystal composition by combining the base liquid crystal compounds with specifically designed self-aligning additives. This composite formulation integrates multiple functional components that work synergistically: the liquid crystal compounds provide the desired electro-optical properties while the self-aligning additives provide the alignment function, achieving both cost effectiveness and performance requirements.
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 polymerizable compound ensures excellent storage characteristics and uniform vertical alignment of liquid crystal molecules, even without polyimide layers, improving electro-optical performance and reducing production costs.
Implementation Method 1
A polar-group-containing polymerizable compound represented by general formula (i) is used in a liquid crystal composition to achieve vertical alignment of liquid crystal molecules
Data Source
AI summary
The compound is represented by general formula (i). In the compound, in a group Ki1, at least two secondary carbon atoms in an alkyl group (a linear alkyl, halogenated alkyl, or cyanogenated alkyl group having 3 to 40 carbon atoms) are replaced with —C(═Xi1)— and/or —CH(—CN)—, where Xi1 is an oxygen atom, a sulfur atom, NH, or NR13; in addition, a group Ai2, a group Ai3, or the group Ki1 includes, as a substituent, at least one Pi1-Spi1- group, where Pi1 is a polymerizable group, and SPi1 is a spacer group or a single bond. The liquid crystal composition including the compound represented by general formula (i) can be adsorbed onto substrates between which a liquid crystal layer is held, and, consequently, without the use of an alignment film, liquid crystal molecules can be maintained in a state in which the liquid crystal molecules are aligned in a vertical direction.