Polyimide Precursor Solution for High-Solid, Low-Viscosity Coating

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Solution Overview

Problem

Existing polyimide precursor solutions suffer from poor storage stability, high viscosity, and limited solubility, which affects their use in high-temperature processes and transparency, making it difficult to produce flexible devices with desired mechanical, thermal, and optical properties.

Innovation Solution

A polyimide precursor solution is formulated using an amide-based organic solvent with a positive distribution coefficient (Log P) and density of 1 g/cm³ or less, such as diethylpropionamide (DEPA), maintaining a high solid content of 12% and low viscosity of 7000 mPa*s or less, to reduce interaction and phase separation, thereby improving processability and transparency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If polyimide precursor solution is used with high solid content, then heat resistance and mechanical properties are improved, but viscosity increases making coating difficult

Engineering Contradiction:

Improveheat resistanceVSAvoidcoating processability

Core Design Contradiction:

TemperatureVSEase of operation

Solution Approach 1:

The patent changes the chemical composition parameters of the solvent system by selecting specific amide-based solvents with particular molecular structures and properties. This allows achieving low viscosity at high solid content (10-20 wt%) by optimizing the solvent's interaction with polyamic acid, resolving the contradiction between heat resistance and coating processability

Inventive Principle:

Principle #35Parameter changes

2Reliability

If polyimide precursor solution storage stability is improved, then application and curing processes become stable, but this requires avoiding hydrolysis which limits solvent choices

Engineering Contradiction:

Improvestorage stabilityVSAvoidsolvent selection flexibility

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent applies local quality by selecting solvents with specific local molecular characteristics - amide-based solvents with particular structural features that provide both hydrolysis resistance and compatibility with polyamic acid. This targeted selection achieves storage stability while maintaining processability

Inventive Principle:

Principle #3Local quality

3Ease of operation

If imidized polyimide resin solubility is improved, then coating application becomes easier, but heat resistance is reduced

Engineering Contradiction:

Improvecoating applicationVSAvoidheat resistance

Core Design Contradiction:

Ease of operationVSTemperature

Solution Approach 1:

The patent applies preliminary action by using amide-based solvents that maintain polyamic acid in a stable, soluble state before imidization. The solvent's molecular structure is selected to ensure good dissolution and coating application, and only after coating is complete does the imidization process occur, at which point heat resistance is achieved

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentEP3578590B1Polyimide precursor solution and polyimide film produced using same

Publication Date: 2025.11.05 LG CHEM LTD

Figure 1~2

AI summary

The present invention relates to the production of a polyimide precursor, whereby, by using an amide-based organic solvent having a positive-number partition coefficient (LogP) and a density of at most 1 g/cm3, an interaction between the organic solvent and polyamic acid, which is a polyimide precursor, may be mitigated, thereby enabling the decrease of the viscosity of a polyimide precursor solution, and thus enabling a polyimide precursor solution having high solid content and low viscosity to be obtained.