Polymerizable Liquid Crystal Composition for Homeotropic Alignment
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Solution Overview
Problem
Current liquid crystal display (LCD) technologies face challenges with viewing angle dependency and color shift, particularly in larger displays, due to limitations in controlling the phase difference in the thickness direction of retardation films and the requirement for high-temperature heat treatment in forming homeotropic alignment liquid crystal films.
Innovation Solution
A polymerizable liquid crystal composition with homeotropic alignment, comprising specific compounds represented by Formulas 1 and 2, which include cyclohexyl or bicyclohexyl groups for vertical alignment and a mesogenic core with two rings, allowing for improved vertical alignment and reduced need for additional alignment accelerators, is applied to a substrate to form an optical film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a homeotropic alignment liquid crystal film is formed using conventional methods, then vertical alignment is achieved, but high-temperature heat treatment (60-300°C for 20-30 minutes) is required which is difficult to apply to continuous high-speed processes
Solution Approach 1:
The patent replaces the thermal field (heat treatment) with a photopolymerization field. Instead of using high-temperature heat treatment to achieve homeotropic alignment, the invention uses photopolymerizable liquid crystal compounds that can be cured at low temperatures through UV irradiation or other polymerization methods, thereby achieving vertical alignment without the need for high-temperature processing that limits production speed.
Solution Approach 2:
The patent changes the fundamental parameter of alignment temperature from high (60-300°C) to low (room temperature or slightly elevated). By using photopolymerizable liquid crystal compounds with specific molecular structures containing polymerizable groups, the alignment process can be initiated and completed at much lower temperatures through photopolymerization, enabling continuous high-speed manufacturing processes.
2Manufacturing precision
If heat shrinkable films are used to control phase difference in thickness direction, then some phase difference control is achieved, but the method is limited in extending film in thickness direction and cannot control phase difference over a wide range
Solution Approach 1:
The patent changes the approach to phase difference control by using liquid crystal compounds with specific mesogenic core structures (two rings) and polymerizable groups. By varying the molecular structure, chain length, and composition ratios of the liquid crystal compounds, the phase difference in the thickness direction can be controlled over a wide range without relying on heat shrinkable films, thereby achieving both precision and versatility.
Solution Approach 2:
The patent employs composite liquid crystal compositions containing multiple components including polymerizable liquid crystal compounds with cyclohexyl or bicyclohexyl groups, mesogenic cores with two rings, and potentially other additives. This composite approach allows fine-tuning of the phase difference properties while maintaining vertical alignment, providing both precision control and wide adaptability range that single-component systems cannot achieve.
3Manufacturing precision
If retardation films with thickness of 50-100 microns are used, then phase difference control is improved, but the thickness reduction requirement cannot be satisfied
Solution Approach 1:
The patent achieves precise phase difference control in thin films by changing the molecular parameters of the liquid crystal compounds. By using compounds with specific mesogenic cores (two rings), appropriate chain lengths, and optimized composition ratios, the patent can achieve the required phase difference in much thinner films (significantly less than 50 microns) compared to conventional retardation films, thereby satisfying both precision and thickness reduction 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 composition enables the production of optical films with enhanced vertical alignment properties, reducing defects and improving viewing angle and color shift performance, suitable for use in LCDs without the need for high-temperature treatments or extensive thickness control.
Implementation Method 1
it has become known recently to manufacture an optical film by coating a polymerizable liquid crystal material on a substrate of an alignment film, aligning the coated material, and fixing the aligned material through exposure
Data Source
AI summary
Disclosed is a polymerizable liquid crystal composition which is applicable on a supporting substrate, such as a transparent plastic film for optical use, or glass, etc., and has a homeotropic alignment. Also, disclosed is an optical film obtained by aligning and fixing the polymerizable composition on a substrate.