Vertical Alignment Layer for Liquid Crystal Displays
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional liquid crystal displays face challenges in aligning liquid crystal molecules with positive dielectric anisotropy, leading to difficulties in achieving optimal black level expression and reducing afterimages, particularly under high voltage conditions.
Innovation Solution
The use of an alignment layer with a main chain and side chains containing vertical and polar functional groups, where the vertical functional group is predominantly at the upper part and the polar group at the lower part, along with a polyimide main chain, to vertically align liquid crystal molecules and facilitate charge transfer, thereby improving alignment stability and reducing afterimages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional alignment layers are used to align liquid crystal molecules with positive dielectric anisotropy, then the alignment function is provided, but optimal black level expression and afterimage reduction are not achieved under high voltage conditions
Solution Approach 1:
The alignment layer is designed with different functional groups at different locations: vertical functional groups (such as cyano groups) are positioned at the upper part to provide strong vertical alignment force, while polar functional groups are positioned at the lower part to facilitate charge transfer. This spatial differentiation of functional properties resolves the contradiction by providing location-specific functions that simultaneously achieve stable alignment and afterimage reduction.
Solution Approach 2:
The alignment layer is constructed as a composite material containing multiple types of functional groups (vertical functional groups and polar functional groups) within a single layer structure. This composite approach allows the layer to simultaneously exhibit both strong vertical alignment capability and effective charge transfer properties, thereby resolving the contradiction between alignment stability and afterimage reduction.
2Speed
If high voltage is applied to improve response speed, then the response performance is enhanced, but afterimages are intensified
Solution Approach 1:
The polar functional groups in the alignment layer act as an intermediary mechanism that facilitates charge transfer between the liquid crystal molecules and the alignment layer. This intermediary charge transfer pathway provides an alternative discharge route for accumulated charges, thereby reducing afterimages even when high voltage is applied for fast response.
3Ease of manufacture
If the alignment layer structure is simplified, then the manufacturing process is easier, but the ability to reduce afterimages and improve black level expression is compromised
Solution Approach 1:
Rather than changing the fundamental single-layer structure of the alignment layer, the invention optimizes the chemical composition parameters by incorporating specific ratios of vertical functional groups and polar functional groups. This parameter optimization achieves afterimage reduction functionality while maintaining the simplicity of the single-layer manufacturing process.
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 configuration enhances the vertical alignment of liquid crystal molecules, reduces afterimages by more than 40 grays, and improves the intensity of surface afterimages by over 10 times, while maintaining processability and reliability.
Implementation Method 1
the vertical functional group may be disposed at an upper part of the alignment layer... The liquid crystal molecules may be aligned in a vertical direction with respect to the first substrate or the second substrate
Implementation Method 2
the polar group may be disposed at a lower part of the alignment layer... facilitates charge transfer, thereby improving alignment stability and reducing afterimages
Implementation Method 3
The liquid crystal display generates an electric field in a liquid crystal layer by applying a voltage to the field generating electrodes, which determines a direction of liquid crystal molecules of the liquid crystal layer to display an image by controlling polarization of incident light
Data Source
AI summary
A liquid crystal display includes: a first substrate and a second substrate facing each other; a pair of field generating electrodes disposed on the first substrate; a liquid crystal layer disposed between the first substrate and the second substrate and including liquid crystal molecules having positive dielectric anisotropy; and at least one alignment layer disposed between the first substrate and the second substrate, wherein the alignment layer includes a main chain and at least one side chain connected to the main chain, and the side chain includes a vertical functional group or a polar group.