Liquid Crystal Aligning Agent Imidization Rate and Residual Image Reduction

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Solution Overview

Problem

Conventional liquid crystal display technologies face limitations in maintaining high liquid crystal alignment performance and imidization rate under AC and DC driving conditions, particularly due to residual images caused by additives used in the photo-crosslinking materials and lower imidization rates in polyamic acid ester-based polyimides.

Innovation Solution

A liquid crystal aligning agent comprising a polyimide precursor and polyimide with specific terminal groups, which undergo a [2+2] cycloaddition reaction upon polarized ultraviolet light irradiation, enhancing imidization rates without the need for additives and minimizing residual images.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If polyamic acid ester-based polyimide precursors are used as photo-crosslinking materials, then liquid crystal alignment performance is improved, but imidization rate decreases

Engineering Contradiction:

Improveliquid crystal alignment performanceVSAvoidimidization rate

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent modifies the chemical structure parameters of the polyimide precursor by introducing specific terminal groups (carboxyl, hydroxyl, or amino groups) to enhance the imidization rate while preserving the alignment performance provided by the polyamic acid ester-based structure

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention creates a composite molecular structure combining polyamic acid ester backbone with functional terminal groups, achieving both high alignment performance and high imidization rate through the synergistic effect of different functional groups within the same molecule

Inventive Principle:

Principle #40Composite materials

2Productivity

If additives such as base catalysts and amino acids are used to improve imidization rate, then imidization rate increases, but liquid crystal alignment properties are reduced due to residual additives

Engineering Contradiction:

Improveimidization rateVSAvoidliquid crystal alignment properties

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent extracts the imidization-promoting function from external additives and incorporates it directly into the polyimide precursor molecule through functional terminal groups, eliminating the need for separate additive substances that would leave harmful residues

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The polyimide precursor with functional terminal groups performs self-catalysis during the imidization process, eliminating the need for external base catalysts and amino acids, thereby preventing residual image formation while maintaining high imidization rate

Inventive Principle:

Principle #25Self-service

3Reliability

If conventional photo-crosslinking materials are used, then alignment performance is maintained, but residual images occur under AC driving conditions

Engineering Contradiction:

Improvealignment performanceVSAvoidresidual images

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent converts the potential harm of incomplete imidization (which causes residual images) into a benefit by using functional terminal groups that promote complete imidization, thereby eliminating residual images while maintaining the alignment performance of photo-crosslinking materials

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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

The solution maintains consistent liquid crystal alignment performance under AC driving and reduces residual images by increasing imidization rates, thereby improving the overall performance of the liquid crystal alignment layer.

Implementation Method 1

A liquid crystal aligning agent comprising a polyimide precursor and polyimide having a specific terminal group, and capable of increasing an imidization rate upon polarized ultraviolet light irradiation by a [2+2] cycloaddition reaction

Methodology Applied

Scientific Effect[2+2] cycloaddition reaction: Photopolymerisation

Implementation Method 2

The photochemical classification of photochemical materials can be divided into groups as follows. The first group consists of materials containing photosensitive species that undergo a trans-cis photoisomerization reaction... The third group, which is mainly studied, includes materials undergoing photo-cross-linking in the form of a cycloaddition

Methodology Applied

Scientific EffectPhotochemical reaction: Photopolymerisation

Implementation Method 3

among the photo-crosslinking materials, polyamic acid ester-based polyimide precursors show a slightly lower degree of imidization in the curing process for preparing a liquid crystal alignment layer

Methodology Applied

Scientific EffectImidization reaction:

Data Source

PatentUS10526540B2Liquid crystal aligning agent, liquid crystal alignment layer comprising the same and method for preparing liquid crystal alignment layer

Publication Date: 2020.01.07 LG CHEM LTD

AI summary

The present invention relates to a liquid crystal aligning agent for use as an alignment layer for liquid crystal display. More specifically, the present invention relates to a liquid crystal aligning agent capable of improving an imidization rate and thus exhibiting an excellent alignment state, a liquid crystal alignment layer comprising the same, a preparation method thereof and a liquid crystal display comprising the liquid crystal alignment layer.