Liquid Crystal Aligning Agent Low-Temperature Baking

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Solution Overview

Problem

Current liquid crystal display elements require high-temperature baking to remove solvents like N-methyl-2-pyrrolidone, which is energy-intensive, and existing methods for achieving low-temperature baking in vertical alignment systems are inefficient, leading to instability in pretilt angles and potential display burn-in.

Innovation Solution

A liquid crystal aligning agent with a polymer containing isocyanate or blocked isocyanate groups and photoreactive side chains, which allows for low-temperature crosslinking and alignment regulation under polarized ultraviolet irradiation, maintaining stable pretilt angles even under external stress.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If high-temperature baking is used to remove NMP solvent, then solvent removal is complete, but energy consumption increases and plastic substrates may be damaged

Engineering Contradiction:

Improveenergy consumptionVSAvoidpretilt angle stability

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent changes the chemical parameters of the aligning agent by introducing isocyanate groups that react with hydroxyl or amino groups to form crosslinked structures. This chemical modification enables the film to achieve stable pretilt angles at lower baking temperatures (80-150°C), reducing energy consumption while maintaining reliability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite crosslinked structure by combining the aligning agent polymer with crosslinking agents containing hydroxyl or amino groups. This composite material system provides both the alignment function and thermal stability at reduced temperatures, resolving the contradiction between energy efficiency and performance reliability

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If polyimide liquid crystal alignment films are used, then alignment function is achieved, but high-temperature baking is required due to low solvent solubility

Engineering Contradiction:

Improvemanufacturing process simplicityVSAvoidbaking temperature

Core Design Contradiction:

Ease of manufactureVSTemperature

Solution Approach 1:

The patent modifies the molecular structure parameters of the alignment film by incorporating isocyanate groups that undergo crosslinking reactions. This structural change allows the use of lower boiling point solvents and reduces the baking temperature from 200°C to 80-150°C, making the manufacturing process easier while maintaining film quality

Inventive Principle:

Principle #35Parameter changes

3Reliability

If conventional alignment methods are used, then liquid crystal alignment is achieved, but pretilt angles become unstable under external stress

Engineering Contradiction:

Improvepretilt angle stabilityVSAvoidenergy cost

Core Design Contradiction:

ReliabilityVSUse of energy by stationary object

Solution Approach 1:

The patent applies preliminary crosslinking action during the baking process, where isocyanate groups react with hydroxyl or amino groups to form stable crosslinked networks before the liquid crystal is assembled. This preliminary structural stabilization ensures pretilt angle stability under external stress without requiring additional energy-intensive processes later

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces mechanical rubbing methods with photoalignment and chemical crosslinking mechanisms. The isocyanate-based crosslinking provides stable pretilt angles through chemical bonding rather than mechanical alignment, reducing energy consumption while improving reliability

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

Enables low-temperature baking of liquid crystal alignment films with improved stability of pretilt angles, reducing energy consumption and preventing display burn-in during long-term use.

Implementation Method 1

a site having a photoreactive group having photoalignment

Methodology Applied

Scientific EffectPhotochemical reaction: Photopolymerisation

Implementation Method 2

a site having an isocyanate group and/or a blocked isocyanate group; and (b) a site having at least one functional group selected from an amino group and a hydroxyl group

Methodology Applied

Scientific EffectChemical bonding: Chemical Bonding

Data Source

PatentUS10921650B2Liquid crystal aligning agent, liquid crystal alignment film and liquid crystal display element

Publication Date: 2021.02.16 NISSAN CHEM CORP

AI summary

The present invention relates to a liquid crystal aligning agent which contains a polymer that has a site having an isocyanate group and/or a blocked isocyanate group, a site having a photoreactive group having photoalignment, and a site having at least one functional group selected from an amino group and a hydroxyl group in each molecule. The present invention provides a liquid crystal display element which enables baking at low temperatures during the formation of a liquid crystal alignment film by a photoalignment method, the liquid crystal alignment film being able to be imparted with alignment regulating property and pretilt angle developing property.