Polyamide-imide film transparency via cyclo-olefin and fluorine

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Solution Overview

Problem

Polyimides used in display applications face challenges with yellow discoloration due to charge transfer complexes, which affect their transparency and suitability as high-temperature, transparent materials.

Innovation Solution

A polyamide-imide film is developed with specific repeating structures and terminal groups that reduce charge transfer between polymer chains, incorporating a polyamide group to enhance mechanical and thermal properties while maintaining transparency, using chemical structures like Chemical Formula 1a-1c and terminal groups like Chemical Formula 1d, and manufacturing methods involving diamine, tetracarboxylic dianhydride, and isocyanate reactions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If aromatic polyimide is used to achieve high mechanical strength and thermal stability, then mechanical properties and thermal resistance are improved, but the material exhibits dark brown color and yellow discoloration due to charge transfer complexes, reducing transparency

Engineering Contradiction:

Improvemechanical strengthVSAvoidyellow discoloration

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The patent modifies the chemical structure parameters of polyimide by replacing aromatic rings with cyclo-olefin structures and introducing fluorinated groups. This changes the electronic properties to reduce charge transfer complexes while maintaining mechanical strength and thermal stability, thereby eliminating yellow discoloration and improving transparency

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite molecular structure combining cyclo-olefin rings, fluorinated groups, and imide linkages within the polymer chain. This composite structure achieves both high mechanical strength through rigid backbone and transparency through reduced electron delocalization, resolving the contradiction between strength and discoloration

Inventive Principle:

Principle #40Composite materials

2Temperature

If polyimide is used for high thermal stability, then thermal resistance is improved, but the thermal expansion coefficient is too high for display applications

Engineering Contradiction:

Improvethermal stabilityVSAvoidthermal expansion coefficient

Core Design Contradiction:

TemperatureVSStability of the object's composition

Solution Approach 1:

The patent introduces fluorinated groups and cyclo-olefin structures that alter the thermal expansion characteristics of the polymer. These structural modifications reduce the thermal expansion coefficient to match display substrate requirements while preserving the high thermal stability needed for processing and application

Inventive Principle:

Principle #35Parameter changes

3Reliability

If polyimide structure is used to achieve excellent chemical resistance, then chemical stability is improved, but solubility in organic solvents is insufficient for solution casting applications

Engineering Contradiction:

Improvechemical resistanceVSAvoidsolubility

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent introduces fluorinated side groups and modifies local molecular structure to enhance solubility without compromising the backbone rigidity that provides chemical resistance. The localized structural changes allow solution processing while maintaining overall chemical stability

Inventive Principle:

Principle #3Local quality

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 polyamide-imide film achieves high mechanical strength, heat resistance, chemical resistance, and transparency, suitable for applications like display substrates and optical films, with improved optical properties and reduced yellowness, enabling its use in flexible displays and electronic components.

Implementation Method 1

it can be explained by the theory of charge transfer complex (hereinafter, called CT-complex) induced by π electrons of benzene within a main chain of the polyimide

Methodology Applied

Scientific EffectCharge transfer complex (CT-complex):

Data Source

PatentEP3366726B1High-strength transparent polyamidimide and method for preparing same

Publication Date: 2019.07.03 LG CHEM LTD

AI summary

The present invention provides a polyamide-imide film which maintains transparency and has highly enhanced mechanical properties and heat resistance. The polyamide-imide shows excellent transparency, heat resistance, mechanical strength and flexibility and thus can be used in various fields such as substrates for devices, cover substrates for displays, optical films, integrated circuit (IC) packages, adhesive films, multi-layer flexible printed circuits (FPC), tapes, touch panels and protective films for optical disks.