Photoalignment Composition Stabilizing Pre-Tilt Angle Against Ionic Contamination

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Current photoalignment compositions for liquid crystal displays face challenges in maintaining stable pre-tilt angles and resisting ionic contamination, which can lead to display defects such as luminescence non-uniformity, and there is a need for more economical and effective compositions that do not compromise electrical characteristics.

Innovation Solution

The development of photoalignment compositions comprising polymers from the class of polyimide and/or polyamic acid with specific repeating structural units, combined with photoalignment materials, which provide excellent liquid crystal alignment properties and stability even in the presence of ionic contamination.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional photoalignment compositions are used, then liquid crystal alignment is achieved, but pre-tilt angle stability deteriorates due to ionic contamination

Engineering Contradiction:

Improvepre-tilt angle stabilityVSAvoidionic contamination sensitivity

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies silane coupling agents that react with ionic contaminants to convert the harmful ionic contamination into beneficial crosslinked structures. The silane groups form covalent bonds with ionic impurities, transforming them from destabilizing agents into structural components that enhance pre-tilt angle stability and resistance to further contamination.

Inventive Principle:

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

Solution Approach 2:

The invention creates a composite alignment layer combining polyimide or polyamic acid polymers with silane coupling agents. This composite structure provides both the liquid crystal alignment functionality of the polymer and the contamination-resistant properties of the silane crosslinked network, achieving synergistic effects that stabilize pre-tilt angle despite ionic contamination.

Inventive Principle:

Principle #40Composite materials

2Reliability

If photoalignment compositions with high resistance to ionic contamination are developed, then pre-tilt angle stability improves, but composition complexity increases

Engineering Contradiction:

Improvepre-tilt angle stabilityVSAvoidcomposition complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent modifies the chemical composition parameters by incorporating specific silane coupling agents with controlled silane group content (typically 1-10 wt% of total composition). By adjusting these parameters within optimized ranges, the composition achieves enhanced contamination resistance without requiring fundamental structural changes or excessive complexity.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If conventional alignment materials are used, then liquid crystal alignment is achieved, but voltage holding ratio decreases due to ionic contamination

Engineering Contradiction:

Improvevoltage holding ratioVSAvoidionic contamination

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The silane coupling agents react with ionic contaminants to form covalent crosslinked structures, converting the harmful ionic charges that cause voltage leakage into neutral crosslinked networks. This transformation maintains electrical insulation properties and preserves voltage holding ratio even in the presence of contamination.

Inventive Principle:

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

Solution Approach 2:

The silane coupling agents act as intermediary substances between the alignment layer and ionic contaminants. They provide a chemical bridge that captures ionic impurities before they can reach and destabilize the liquid crystal layer, thereby protecting the electrical characteristics of the display device.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

These compositions effectively stabilize the pre-tilt angle of liquid crystals and maintain high voltage holding ratios, reducing display defects and ensuring uniform performance despite ionic contamination.

Implementation Method 1

The polymers in the layer are thereby oriented into one direction and this orientation information is then induced on the adjacent liquid crystal layer... irradiated with polarized light

Methodology Applied

Scientific EffectAbsorption (EM radiation): Absorption (EM radiation)

Implementation Method 2

These materials are known for their outstanding physical properties, such as heat resistance, affinity to the liquid crystal materials and mechanical strength. Such polymers are said to be photoreactive, if they react upon irradiation with polarized or unpolarized light by orienting themselves into one direction

Methodology Applied

Scientific EffectPhotopolymerisation: Photopolymerisation

Data Source

PatentUS11561440B2Photoalignment composition for the stabilization of the pre-tilt angle in liquid crystal layers

Publication Date: 2023.01.24 ROLIC TECHNOLOGIES AG

AI summary

The present invention relates to a photoalignment composition for the alignment of liquid crystals and the stabilization of the pre-tilt angle in liquid crystal layers. Further the present invention relates to the liquid crystal alignment film and coating layer prepared from the said composition and the use to fabricate optical and electrooptical elements and devices.