Polyimide Film Composition for Flat Flexible Display Substrates

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing polyimide materials used in flexible display devices suffer from reduced emission efficiency and optical properties due to differences in refractive indices and deterioration at high temperatures, leading to potential damage and loss of flatness.

Innovation Solution

A polyimide-based resin film with a specific structure, containing a polyimide repeating unit and a tetravalent functional group derived from tetracarboxylic dianhydride and an aromatic diamine with electron-withdrawing groups, which ensures high heat resistance and maintains flatness during high-temperature curing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If conventional polyimide materials are used in flexible display devices, then the device can be manufactured with flexible substrates, but the emission efficiency is reduced due to refractive index differences between the polyimide layer and multilayer inorganic film

Engineering Contradiction:

Improveemission efficiencyVSAvoidrefractive index mismatch

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent modifies the chemical structure of polyimide by introducing specific aromatic diamine components with electron-donating groups and controlling the molecular weight distribution. This changes the refractive index parameter of the polyimide material to better match the multilayer inorganic film, thereby reducing light reflection and improving emission efficiency without adding complex device structures

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite polyimide system by combining different aromatic diamine monomers (such as m-phenylenediamine and p-phenylenediamine) with specific ratios, and controlling the polymerization process to achieve optimal refractive index matching. This composite approach allows tuning of optical properties while maintaining the flexibility and heat resistance required for display applications

Inventive Principle:

Principle #40Composite materials

2Temperature

If polyimide is cured at high temperature of 400°C or more, then heat resistance is improved, but optical properties deteriorate due to polyimide degradation

Engineering Contradiction:

Improveheat resistanceVSAvoidoptical properties

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The patent optimizes the curing temperature parameter and time parameters based on the specific polyimide composition. By controlling the curing process parameters (temperature profile, atmosphere, duration) and adjusting the polyimide molecular structure (molecular weight, aromatic content), the material achieves sufficient heat resistance at lower curing temperatures, preventing optical degradation while maintaining thermal stability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent ensures continuous stabilization of optical properties through controlled polymerization and curing processes. The gradual cross-linking and imidization reactions are managed to proceed continuously without sudden structural changes that would cause degradation, maintaining optical clarity while achieving the required heat resistance

Inventive Principle:

Principle #20Continuity of useful action

3Temperature

If high temperature heat treatment is applied to polyimide, then heat resistance is improved, but flatness deteriorates due to bowing and warping

Engineering Contradiction:

Improveheat resistanceVSAvoidflatness

Core Design Contradiction:

TemperatureVSShape

Solution Approach 1:

The patent adjusts the polyimide molecular weight parameters and compositional parameters (aromatic diamine content, cross-linking density) to reduce thermal expansion anisotropy. By optimizing these material parameters, the film exhibits more uniform thermal expansion behavior during high-temperature treatment, minimizing bowing and warping while achieving the required heat resistance

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces localized cross-linking structures and aromatic rigid segments at specific positions in the polyimide chain to reinforce areas prone to deformation. This creates local structural reinforcement that resists thermal warping while maintaining overall film flexibility and heat resistance

Inventive Principle:

Principle #3Local quality

4Ease of manufacture

If conventional polyimide is used as substrate, then manufacturing is simplified, but metal layers are damaged during high temperature curing

Engineering Contradiction:

Improvesubstrate processingVSAvoidmetal layer damage

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The patent lowers the curing temperature parameter from conventional high temperatures (400°C or more) to an optimized range (200-350°C) by modifying the polyimide composition with specific aromatic diamines and controlling molecular weight. This temperature reduction eliminates thermal damage to metal layers while maintaining substrate processing simplicity and final material performance

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS12552900B2Polyimide-based polymer film, substrate for display device, and optical device using the same

Publication Date: 2026.02.17 LG CHEM LTD

AI summary

The present disclosure relates to a polyimide-based resin film which is synthesized by the reaction of an acid anhydride compound and a diamine compound having a specific structure, thereby capable of ensuring excellent flatness even under high temperature heat treatment conditions, and stably maintaining flatness even during further heat treatment, a substrate for display device, and an optical device using the same.