Polymerizable Liquid Crystal Composition for Display Stability
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Solution Overview
Problem
PSA liquid crystal displays face issues such as image sticking, uneven display, and instability in pretilt angle due to insufficient structural rigidity of polymerizable compounds, residual unpolymerized compounds, and sensitivity to UV light, leading to reduced reliability and increased production costs.
Innovation Solution
A liquid crystal composition containing specific polymerizable compounds with improved voltage holding ratio, faster polymerization rate, and enhanced pretilt angle stability, formulated with compounds of general Formula I, II, and M, which provide better solubility and reduced surface roughness, enabling complete polymerization and improved display performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polymerizable compounds are used in PSA liquid crystal displays, then the display can be manufactured with standard materials, but the structural rigidity is insufficient leading to image sticking and pretilt angle instability
Solution Approach 1:
The patent modifies the chemical structure of polymerizable compounds by introducing rigid cyclic groups (cyclohexyl, phenyl) and adjusting molecular weight and functional group configurations. This changes the physical and chemical parameters of the compounds to achieve both sufficient structural rigidity for preventing image sticking and appropriate solubility for manufacturing
Solution Approach 2:
The patent creates composite liquid crystal compositions by combining multiple polymerizable compounds with different molecular structures, including cyclic groups and various functional groups. This composite approach allows the mixture to achieve optimal balance between rigidity, solubility, and polymerization performance that individual compounds cannot provide alone
2Reliability
If UV photopolymerisation is performed in two steps (UV1 and UV2) to ensure complete polymerization, then residual unpolymerized compounds are reduced, but production time increases and tact time exceeds 2 hours
Solution Approach 1:
The patent designs polymerizable compounds with optimized molecular weight ranges (50-500 for first compound, 50-200 for second compound) and specific functional group configurations that enhance UV absorption efficiency and polymerization reactivity. This allows complete polymerization to occur faster, reducing the required UV exposure time and enabling production within the 2-hour tact time
Solution Approach 2:
The patent formulates the liquid crystal composition with pre-optimized ratios of polymerizable compounds (0.01-5 wt% for first compound, 0.01-3 wt% for second compound) and compatible host liquid crystal compounds that facilitate rapid and complete polymerization. This preliminary optimization of composition ensures that the polymerization process completes efficiently without requiring extended UV2 treatment time
3Productivity
If high UV radiation intensity is applied in UV2 step to complete polymerization quickly, then production time is reduced, but negative effects like image sticking and reduced reliability increase
Solution Approach 1:
The patent selects polymerizable compounds with specific molecular structures that have appropriate UV absorption characteristics and polymerization reactivity. The cyclic groups and functional groups are chosen to ensure controlled polymerization that proceeds efficiently without excessive heat generation or side reactions, allowing moderate UV intensity to achieve complete polymerization without harmful effects
Solution Approach 2:
The patent uses the first polymerizable compound (with cyclic group) as the primary structure that forms the backbone of the polymer network, and the second polymerizable compound as a complementary component that enhances crosslinking. This dual-compound approach creates a robust polymer structure that prevents image sticking while allowing controlled polymerization at moderate UV intensities
4Stability of the object's composition
If polymerizable compounds with rigid structures are used to prevent pretilt angle changes, then pretilt angle stability improves, but solubility in liquid crystal composition decreases and spontaneous polymerization risk increases
Solution Approach 1:
The patent optimizes the molecular weight and structural complexity of polymerizable compounds to achieve a balance: the cyclic groups provide necessary rigidity for pretilt angle stability, while controlled molecular weight ranges and flexible spacer groups maintain solubility in the liquid crystal host composition
Solution Approach 2:
The patent combines multiple polymerizable compounds with complementary structures in specific ratios. The first compound with cyclic group provides rigidity, while the second compound with different functional groups enhances solubility and prevents spontaneous polymerization. This composite formulation achieves both pretilt angle stability and compatibility with liquid crystal host
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 proposed liquid crystal composition achieves higher voltage holding ratio, faster response speed, reduced residual polymer content, and improved pretilt angle stability, effectively addressing issues like image sticking and uneven display, thereby enhancing the reliability and efficiency of PSA liquid crystal displays.
Implementation Method 1
the polymerizable compounds contained in the liquid crystal composition are polymerized or crosslinked in situ, usually by UV photopolymerisation, which is achieved by exposing the liquid crystal composition to UV radiation
Data Source
AI summary
A liquid crystal composition includes at least one compound of general Formula I, at least one compound of general Formula II and at least one compound of general Formula M. The polymerizable liquid crystal composition provides a higher VHR (especially an excellent VHR after UV irradiation), a lower surface roughness of the polymer layer, a faster polymerization rate, a lower residual amount of the polymerizable compound and a better pretilt angle stability, which enables the production of a liquid crystal display device with a better voltage stability and a faster response speed, and can effectively reduce or prevent the occurrences of problems such as “burn-in”, “image sticking”, “Zara Particle” and “uneven display” in the liquid crystal display device. A liquid crystal display includes the liquid crystal composition.