Liquid Crystal Display Polymer Layer Alignment
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Solution Overview
Problem
Existing liquid crystal display devices using multi-domain vertical alignment (MVA) mode face issues with display defects and reduced voltage holding ratio due to materials and production conditions, particularly with monomers and polymerization initiators that cause alignment defects and residual impurities.
Innovation Solution
Incorporating radical polymerizable monomers that generate radicals through self-cleavage reactions upon light exposure, with at least two radical polymerizable groups, and using a self-cleaving photopolymerization initiator with a polymerizable group to form a polymer layer without alignment films, ensuring stable alignment and maintaining voltage holding ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional monomers and polymerization initiators are used to form a polymer layer without alignment films, then alignment control is achieved, but display defects occur and voltage holding ratio decreases
Solution Approach 1:
The patent changes the chemical parameters of the polymerization system by using specific monomers (formula 1-3) with controlled molecular structures and functionalities. The polymerization conditions including light source wavelength (365nm UV-LED), irradiation dose (5-500mJ/cm²), and temperature (20-100°C) are precisely controlled to achieve complete polymerization without residual monomers, thereby maintaining high voltage holding ratio while eliminating alignment films
Solution Approach 2:
The patent employs composite liquid crystal compositions containing multiple components: liquid crystal compounds (formula 201-206), specific monomers (formula 1-3), and polymerization initiators (formula 4-6). This composite approach ensures proper alignment control through the polymer layer while preventing display defects and maintaining electrical properties through synergistic interactions among components
2Manufacturing precision
If polymerization is initiated using conventional initiators, then polymer layer formation is achieved, but residual initiator molecules remain and cause voltage holding ratio reduction
Solution Approach 1:
The patent optimizes polymerization parameters including using UV-LED at 365nm wavelength with controlled irradiation dose (5-500mJ/cm²) and temperature (20-100°C) to ensure complete polymerization of monomers. These parameter controls minimize residual initiator molecules in the liquid crystal layer, preventing voltage holding ratio reduction while achieving proper polymer layer formation
Solution Approach 2:
The patent uses polymerization initiators (formula 4-6) that decompose completely after initiating polymerization, leaving no persistent residual molecules. The initiators serve their purpose temporarily and then break down, unlike conventional initiators that leave stable residual molecules that interfere with electrical properties
3Extent of automation
If monomers with single polymerizable groups are used, then polymerization occurs, but alignment control is insufficient
Solution Approach 1:
The patent uses composite monomer systems including both monofunctional monomers (formula 1) and difunctional monomers (formula 2-3). The monofunctional monomers ensure complete polymerization and high voltage holding ratio, while the difunctional monomers create crosslinked structures that enhance alignment control. This composite approach achieves both adequate alignment control and electrical stability
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
This approach prevents display defects and reduces voltage holding ratio degradation, resulting in a reliable liquid crystal display device with improved display qualities and reduced long-term exposure risks.
Implementation Method 1
at least one kind of the radical polymerizable monomers being a compound generating radicals through a self-cleavage reaction by exposure to light
Implementation Method 2
a self-cleaving photopolymerization initiator with a polymerizable group to form a polymer layer
Data Source
AI summary
The present invention provides a liquid crystal display device in which display defects and reduction in the voltage holding ratio are not likely to occur even without alignment films. That is, the liquid crystal display device of the present invention includes: a pair of substrates each substantially having no alignment film; a liquid crystal layer which is disposed between the pair of substrates and contains a liquid crystal material; and a polymer layer which is formed on a surface of at least one of the substrates and controls alignment of liquid crystal molecules, the polymer layer being formed by polymerization of one or more kinds of radical polymerizable monomers added to the liquid crystal layer, at least one kind of the radical polymerizable monomers being a compound generating radicals through a self-cleavage reaction by exposure to light and having at least two radical polymerizable groups.