Multireactive Polymerizable Compounds for PSA Displays
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Solution Overview
Problem
Current liquid-crystal display (LCD) technologies, particularly in PSA displays, face challenges such as inadequate tilt or voltage holding ratio, unsuitable reactive mesogens, residual unpolymerized materials causing image sticking, and difficulties in achieving rapid and complete polymerization, leading to issues like image burn and reduced display performance.
Innovation Solution
The use of multireactive polymerizable compounds based on coumarine or flavone derivatives with two or more polymerizable groups, attached to the same ring, which facilitate low pretilt angles, rapid polymerization, and reduced residual amounts, improving electro-optical properties and preventing image sticking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polymerizable compounds are used in PSA displays, then the display can achieve basic alignment functionality, but the polymerization is slow and incomplete, leaving residual unpolymerized material that causes image sticking
Solution Approach 1:
The patent changes the chemical parameters of the polymerizable compounds by introducing multifunctional monomers with specific molecular structures (containing multiple polymerizable groups per molecule). This structural parameter change enables faster and more complete polymerization, eliminating residual material that causes image sticking while maintaining reliable display performance.
Solution Approach 2:
The patent uses composite material strategies by combining multiple polymerizable groups within single molecular structures (e.g., compounds containing both vinyl and epoxide groups). This creates multifunctional polymer systems that achieve complete crosslinking faster than conventional single-function monomers, resolving the contradiction between polymerization speed and display reliability.
2Reliability
If standard reactive mesogens are used, then the LC medium maintains basic electro-optical properties, but the tilt angle control is inadequate and voltage holding ratio is insufficient
Solution Approach 1:
The patent modifies the molecular parameters of reactive mesogens by incorporating multiple polymerizable functional groups into single molecules. This changes the polymerization kinetics and network formation characteristics, enabling better tilt angle control and improved voltage holding ratio without complicating the manufacturing process.
Solution Approach 2:
The patent applies local quality principles by designing mesogenic groups with specific spatial arrangements of polymerizable groups. This localized structural design enables controlled polymerization in specific regions of the LC cell, achieving adequate tilt angles and voltage holding ratios through targeted molecular architecture rather than global parameter changes.
3Speed
If polymerization is accelerated to improve response times, then faster alignment is achieved, but complete polymerization becomes difficult and residual material increases
Solution Approach 1:
The patent employs composite material strategies by designing molecules that contain multiple different polymerizable groups (e.g., combining vinyl, epoxide, and oxetane groups in single compounds). These multifunctional monomers enable rapid crosslinking through multiple reaction pathways simultaneously, achieving complete polymerization with accelerated response times without leaving residual unpolymerized material.
Solution Approach 2:
The patent applies continuity principles by using monomers with multiple polymerizable groups that can react sequentially or simultaneously through different mechanisms. This continuous multi-pathway polymerization ensures complete conversion of all functional groups, maintaining polymerization completeness while accelerating the overall process to improve response times.
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
These compounds enable faster establishment of desired pretilt angles, complete polymerization, and enhanced specific resistance, threshold voltage, and response times, while minimizing image sticking and residual issues, resulting in improved display performance and production efficiency.
Implementation Method 1
a polymer obtainable by polymerisation of one or more polymerisable compounds according to the invention
Implementation Method 2
the LC medium usually has a negative value of the dielectric (DC) anisotropy. In the switched-off state, the molecules of the LC layer are aligned perpendicular to the electrode surfaces
Implementation Method 3
OCB displays normally contain one or more birefringent optical retardation films in order to prevent undesired transparency to light of the bend cell in the dark state
Data Source
AI summary
The present invention relates to polymerizable compounds, to processes and intermediates for the preparation thereof, and to the use thereof for optical, electro-optical and electronic purposes, in particular in liquid-crystal (LC) media and LC displays, especially in LC displays of the PS (“polymer sustained”) or PSA (“polymer sustained alignment”) type.