Photosensitive Side-Chain Polymer for Liquid Crystal Alignment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The photoalignment method for liquid crystal display elements requires high irradiation amounts of ultraviolet light, leading to instability in alignment and thermal stability, and often uses solvents like chloroform, which is impractical for industrial use, resulting in inefficient alignment treatment and potential display defects.
Innovation Solution
A polymer composition comprising a photosensitive side chain polymer with a vertically alignable group, applied to a substrate, irradiated with polarized ultraviolet light, and then heated to achieve efficient alignment control and improved tilt angle characteristics, eliminating the need for rubbing and reducing solvent issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the photoalignment method uses high irradiation amounts of ultraviolet light, then alignment treatment can be performed, but thermal stability and alignment stability deteriorate
Solution Approach 1:
The patent changes the chemical parameters of the polymer by introducing specific functional groups (carboxyl, hydroxyl, or amine groups) that enable effective photoalignment at lower UV irradiation amounts, thereby improving both productivity and reliability simultaneously
Solution Approach 2:
The patent creates a composite polymer structure combining a main chain (polystyrene, polyacrylonitrile, or polyacrylic acid) with vertically alignable groups and liquid crystalline side chains, achieving stable alignment at reduced UV exposure through the synergistic effect of the composite structure
2Ease of manufacture
If the photoalignment method uses solvents like chloroform, then polymer coating can be achieved, but practical industrial use deteriorates due to safety and environmental concerns
Solution Approach 1:
The patent changes the solvent parameter from hazardous chloroform to safe alternatives (alcohols, esters, ethers, or water) by adjusting the polymer composition to ensure proper dissolution and coating formation without requiring hazardous solvents
Solution Approach 2:
The patent replaces expensive and hazardous solvents with cheaper, safer, and environmentally friendly alternatives that can be easily handled in industrial settings, reducing safety concerns and disposal costs
3Reliability
If the rubbing method is used for alignment treatment, then alignment control ability is achieved, but dust generation and static electricity occur
Solution Approach 1:
The patent replaces the mechanical rubbing system with a photoalignment system that uses UV light irradiation to achieve alignment, eliminating contact-based harmful effects while maintaining alignment control ability through the vertically alignable groups in the polymer structure
4Manufacturing precision
If high definition liquid crystal display elements are produced with electrodes and switching active elements, then display performance is improved, but uniform rubbing of the alignment film deteriorates due to surface unevenness
Solution Approach 1:
The patent replaces the mechanical rubbing process with photoalignment that does not require physical contact with the film surface, allowing uniform alignment treatment even on surfaces with electrodes and switching elements that create unevenness
Solution Approach 2:
The patent changes the alignment mechanism from mechanical rubbing to photochemical alignment, enabling the alignment process to proceed uniformly across the entire surface regardless of underlying structural unevenness
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 provides a highly efficient alignment treatment with enhanced tilt angle characteristics, ensuring stable liquid crystal alignment and improved display performance, even under continuous driving, without the drawbacks of high UV exposure or hazardous solvents.
Implementation Method 1
a photosensitive side chain polymer which is a side chain type polymer having a repeating unit containing a vertically alignable group
Implementation Method 2
irradiating the coating film with polarized ultraviolet light
Implementation Method 3
exhibiting liquid crystallinity in a predetermined temperature range
Implementation Method 4
heating the coating film obtained in [II]
Data Source
AI summary
The present invention relates to a polymer composition which contains (A) a photosensitive side-chain polymer that exhibits liquid crystallinity in a predetermined temperature range and has a repeating unit comprising a vertically aligning group, and (B) an organic solvent. The present invention provides: a liquid crystal alignment film which has excellent tilt angle characteristics, while being provided with alignment controllability with high efficiency; a polymer composition which enables the achievement of this liquid crystal alignment film; a twisted nematic liquid crystal display element; and a vertical field switching mode liquid crystal display element.