Polyimide Liquid Crystal Aligning Agent Adhesion
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Solution Overview
Problem
Liquid crystal display devices face challenges with residual image formation due to alternating-current drive and high temperature exposure, requiring improved liquid crystal alignment films with enhanced adhesion to sealing agents and substrates without compromising liquid crystal alignment properties.
Innovation Solution
A liquid crystal aligning agent containing specific polyimide precursors and imidized polymers with structural units that form amino groups upon heating, enhancing adhesion through interaction with sealing agents and maintaining excellent liquid crystal alignment properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polyimide liquid crystal alignment film is used to control liquid crystal alignment, then liquid crystal alignment property is improved, but adhesion to sealing agents and substrates deteriorates
Solution Approach 1:
The invention introduces amino groups specifically at the molecular ends of the polyimide chain through polyamic acid ester units, creating local polar regions that enhance adhesion without altering the overall polyimide structure and liquid crystal alignment properties. This localized functional group placement resolves the contradiction by providing adhesion enhancement only where needed at the substrate interface.
Solution Approach 2:
The invention creates a composite molecular structure combining regular polyimide units with polyamic acid ester units containing amino groups. This composite approach integrates the liquid crystal alignment capability of polyimide with the adhesion enhancement of amino-containing polyamic acid ester, achieving both improved alignment property and enhanced adhesion simultaneously.
2Strength
If a polyamic acid ester is used in the liquid crystal aligning agent, then adhesion to sealing agents is improved, but electrical resistivity decreases and residual charge increases
Solution Approach 1:
The invention carefully controls the proportion of polyamic acid ester units within 1-50 mol% of the total polymer units. This parameter optimization ensures sufficient adhesion enhancement from the amino groups while limiting the negative electrical effects to acceptable levels, achieving a balance between adhesion and electrical properties.
Solution Approach 2:
The polyamic acid ester units with amino groups are distributed as specific structural components within the polyimide chain, creating localized adhesion-enhancing regions without uniformly degrading the electrical properties throughout the entire film. The amino groups provide adhesion benefit locally while the bulk polyimide structure maintains electrical performance.
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 provides a liquid crystal alignment film with improved adhesion and resistance to long-term use in severe environments, ensuring high reliability and display quality by stabilizing the liquid crystal alignment and enhancing the bonding between substrates.
Implementation Method 1
a liquid crystal aligning agent containing a polyimide precursor having a protecting group to be replaced with a hydrogen atom by heat
Implementation Method 2
a polyimide precursor having a protecting group to be replaced with a hydrogen atom by heat (hereinafter sometimes referred to as a thermally-leaving group)
Data Source
AI summary
To provide a liquid crystal aligning agent to obtain a liquid crystal alignment film which is excellent in the adhesion to a sealing agent and in the liquid crystal alignment property.A liquid crystal aligning agent containing at least one polymer selected from the group consisting of a polyimide precursor having structural units represented by the formula (1) and structural units represented by the formula (3) and an imidized polymer of the polyimide precursor:wherein X1 and X4 are a tetravalent organic group, Y1 is a bivalent organic group having a thermally-leaving group, Y2 is a bivalent organic group, R1 and R2 are a hydrogen atom or a C1-5 alkyl group, and Z1 and Z2 are a hydrogen atom, or a C1-10 alkyl group, C2-10 alkenyl group or C2-10 alkynyl group which may have a substituent.