Liquid Crystal Display Alignment Sustaining Layer
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Solution Overview
Problem
The Polymer Sustained Alignment Technology (PSA) for liquid crystal display devices faces issues with residual photopolymerizable compounds remaining in the liquid crystal layer, leading to image sticking and reliability concerns, which are exacerbated by the limitations of UV dose and increased production costs.
Innovation Solution
Incorporating a nematic liquid crystal material with a terphenyl ring system, which enhances the efficiency of photopolymerization reactions, reducing the residual photopolymerizable compound content to less than 0.015 mol% without increasing the UV dose, and using vertical alignment films with alignment sustaining layers formed from photopolymerized material to regulate pretilt azimuths of liquid crystal molecules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If UV dose is increased to remove residual photopolymerizable compounds, then reliability improves, but production cost increases and manufacturing time increases
Solution Approach 1:
The patent changes the chemical composition parameter of the liquid crystal material by incorporating a photopolymerizable compound with specific molecular structure and reactivity characteristics. This parameter change enables complete polymerization at lower UV doses, resolving the contradiction between reliability (through complete reaction) and manufacturing cost (through reduced UV exposure requirements)
Solution Approach 2:
The patent replaces the conventional approach of using high UV dose (energy-intensive method) with a chemically optimized photopolymerization system. By substituting the mechanical/energy-based solution with a chemically designed system, it achieves complete polymerization at lower energy input, reducing both cost and time while maintaining reliability
2Reliability
If UV dose is increased to remove residual photopolymerizable compounds, then reliability improves, but manufacturing time increases
Solution Approach 1:
The patent modifies the photopolymerization reaction parameters by selecting a compound with high reactivity and appropriate molecular weight. This parameter optimization allows the reaction to reach completion faster at lower UV doses, simultaneously improving reliability through complete polymerization and reducing manufacturing time
Solution Approach 2:
The patent performs preliminary optimization of the photopolymerizable compound selection before the actual polymerization process. By pre-selecting compounds with optimal reactivity characteristics, it ensures that the subsequent UV irradiation step completes the reaction quickly and completely, avoiding the need for prolonged exposure
3Object-generated harmful factors
If photopolymerizable compound content is reduced to minimize residual monomers, then image sticking is reduced, but alignment sustaining layer formation becomes insufficient
Solution Approach 1:
The patent optimizes the concentration parameter of the photopolymerizable compound to a specific range that balances two competing requirements: low enough to minimize residual monomers and prevent image sticking, but high enough to ensure sufficient polymer formation for alignment sustaining. This precise parameter control resolves the contradiction between reducing harmful effects and maintaining functional performance
Solution Approach 2:
The patent applies the concept of local quality by ensuring that the photopolymerizable compound is distributed uniformly throughout the liquid crystal material at an optimized concentration. This uniform distribution ensures that polymerization occurs evenly throughout the layer, providing consistent alignment sustaining properties while minimizing localized residual monomer accumulation that could cause image sticking
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 effectively minimizes residual monomers, reduces image sticking, enhances reliability, and lowers production costs by stabilizing liquid crystal molecule alignment and improving response characteristics without increasing UV exposure.
Implementation Method 1
The polymer is formed by irradiating, after assemblage of a liquid crystal cell, a small amount of polymerizable material (e.g., a photopolymerizable monomer) mixed in a liquid crystal material with active energy rays (e.g., ultraviolet light)
Implementation Method 2
irradiating, after assemblage of a liquid crystal cell, a small amount of polymerizable material (e.g., a photopolymerizable monomer) mixed in a liquid crystal material with active energy rays (e.g., ultraviolet light)
Implementation Method 3
Liquid crystal display devices perform display by utilizing the change of the orientations of liquid crystal molecules which is caused by a voltage applied across the liquid crystal layer
Data Source
AI summary
A liquid crystal display device of the present invention includes: a liquid crystal layer containing a nematic liquid crystal material; a pair of electrodes opposing each other via the liquid crystal layer; a pair of alignment films respectively provided between the pair of electrodes and the liquid crystal layer; and an alignment sustaining layer formed of a photopolymerized material on each of surfaces of the pair of alignment films which are closer to the liquid crystal layer, the alignment sustaining layer being configured to regulate a pretilt azimuth of a liquid crystal molecule of the liquid crystal layer during the absence of an applied voltage across the liquid crystal layer, wherein the pretilt azimuth of the liquid crystal molecule of the liquid crystal layer is regulated by the alignment sustaining layer during the absence of an applied voltage across the liquid crystal layer. The nematic liquid crystal material contains a liquid crystal compound having a terphenyl ring system as an indispensable component, and the liquid crystal layer further contains part of a photopolymerizable compound which is a source material of the photopolymerized material, a content of the photopolymerizable compound relative to the nematic liquid crystal material being less than 0.015 mol %.