Polymer Alignment Control Layer for Liquid Crystal Displays
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Solution Overview
Problem
Liquid crystal display devices face challenges in achieving stable alignment control layers without vertical alignment films, leading to display unevenness and reliability issues due to changes in the alignment control layer over time.
Innovation Solution
A liquid crystal display device is manufactured using a liquid crystal composition containing specific compounds and polymerizable compounds, where the alignment control layer is formed by polymerizing tri- or higher-functional (meth)acrylate and di- or mono-functional (meth)acrylate compounds between substrates without vertical alignment films, using active energy rays and voltage to impart a pre-tilt angle to liquid crystal molecules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If vertical alignment films are omitted to simplify manufacturing and reduce cost, then manufacturing complexity and cost are reduced, but alignment stability deteriorates leading to display unevenness and reliability issues
Solution Approach 1:
The invention extracts and removes the vertical alignment film layer from the conventional liquid crystal display structure, replacing it with a polymer alignment control layer formed directly on the substrate. This eliminates the need for separate alignment film formation processes while maintaining alignment functionality through polymer networks that control liquid crystal orientation.
Solution Approach 2:
The invention uses composite polymer networks formed by combining tri- or higher-functional (meth)acrylate compounds with di- or mono-functional (meth)acrylate compounds. This composite structure provides both the alignment control function and long-term stability, replacing the need for vertical alignment films while ensuring reliable liquid crystal orientation over time.
2Ease of manufacture
If polymerizable compounds are used to form alignment control layers without vertical alignment films, then manufacturing cost is reduced, but alignment stability over time deteriorates causing display quality degradation
Solution Approach 1:
The invention employs a composite polymer system combining crosslinkable compounds (tri- or higher-functional (meth)acrylates) with polymerizable compounds (di- or mono-functional (meth)acrylates). This composite structure creates a stable polymer network that maintains alignment control over long periods while being formed through a single polymerization process that reduces manufacturing cost.
Solution Approach 2:
The invention controls the molecular structure and composition parameters of the polymerizable compounds to achieve optimal stability. By selecting specific functional groups and molecular weights for the (meth)acrylate compounds, the invention ensures the polymer alignment control layer maintains its properties over time without requiring vertical alignment films.
3Adaptability or versatility
If projecting structures are provided to improve viewing angle characteristics, then viewing angle characteristics are improved, but response speed deteriorates due to non-uniform liquid crystal alignment
Solution Approach 1:
The invention removes the projecting structures (such as slits or protrusions) from the substrate and replaces them with a uniform polymer alignment control layer. This eliminates the non-uniform alignment regions near projecting structures while maintaining multi-domain vertical alignment for wide viewing angles, thereby improving response speed.
Solution Approach 2:
The polymer alignment control layer acts as an intermediary between the substrate and the liquid crystal layer, providing uniform alignment control across the entire pixel area. This intermediary layer enables wide viewing angles through controlled pre-tilt angles without the need for projecting structures that would otherwise create response speed variations.
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 method enhances alignment stability and adhesion to substrates, suppressing changes in the alignment control layer, thereby improving display quality and reliability by preventing image sticking and dropping marks while maintaining optimal dielectric and viscosity characteristics.
Implementation Method 1
polymerizing the polymerizable compound in the liquid crystal composition by irradiation with active energy rays
Implementation Method 2
enhances alignment stability and adhesion to substrates
Data Source
Figure 1~2
Figure 3
AI summary
There is provided a liquid crystal display device which suppresses the occurrence of image sticking and dropping marks during manufacture without degrading the characteristics such as dielectric anisotropy, viscosity, nematic phase upper limit temperature, rotational viscosity (γ1), etc. Also, a method for manufacturing the liquid crystal display device is provided. The liquid crystal display device includes a liquid crystal layer which contains a liquid crystal composition and which is held between a substrate having a common electrode and a color filer and a substrate having a plurality of pixels and pixel electrodes of the respective pixels, wherein one or both of the substrates have, without having an alignment film, an alignment control layer formed by using one or more tri- or higher-functional (meth)acrylate compounds and one or more di- or mono-functional (meth)acrylate compounds. The liquid crystal display device is applied to a liquid crystal display device for liquid crystal TV or the like.