Polyamide-imide Film for Foldable Displays

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Solution Overview

Problem

Polyimide-based films deteriorate rapidly in high-temperature or low-temperature environments, leading to compromised mechanical and optical properties, and when used in display devices, they can result in increased haze and decreased adhesion during hard-coating processes, affecting the display's durability and reliability.

Innovation Solution

A polyamide-imide film is developed with a modulus retention value of 75% or more, maintaining mechanical properties at room temperature and elevated temperatures, and a specific thermal treatment process to ensure stability, comprising a polyamide-imide polymer with a modulus of 5 GPa or more and a dMO value of 1% to 8% at -20°C, along with a process involving polymerization of diamine, dianhydride, and dicarbonyl compounds in an organic solvent.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If polyimide-based film is used in high-temperature or low-temperature environment, then the film can provide heat resistance and chemical resistance, but the physical properties are rapidly deteriorated

Engineering Contradiction:

Improveheat resistanceVSAvoidphysical properties

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The patent modifies the chemical composition parameters of the polyimide film by incorporating specific aromatic diamine compounds (40-80 wt%) and aromatic dianhydride compounds (20-60 wt%) to achieve optimal balance between heat resistance and physical property retention at extreme temperatures

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite polyimide film structure combining multiple polymer components with complementary properties, where the aromatic diamine and aromatic dianhydride form a synergistic composite system that maintains mechanical integrity and optical clarity across wide temperature ranges

Inventive Principle:

Principle #40Composite materials

2Temperature

If additives are introduced to improve physical properties at extreme temperatures, then the temperature resistance is enhanced, but the optical properties or compatibility are impaired

Engineering Contradiction:

Improvetemperature resistanceVSAvoidoptical properties

Core Design Contradiction:

TemperatureVSIllumination intensity

Solution Approach 1:

The patent adjusts the compositional parameters to use high-purity aromatic diamine and dianhydride compounds with controlled molecular weights and minimal impurities, achieving temperature resistance without requiring additional additives that would compromise optical clarity

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent ensures homogeneous distribution and reaction of the aromatic diamine and dianhydride components during film formation, creating a uniform polyimide structure that maintains consistent optical properties throughout the material without additive-induced heterogeneity

Inventive Principle:

Principle #33Homogeneity

3Strength

If hard-coating layer is formed on polyimide-based film for display device, then the surface hardness is improved, but the haze increases or adhesion decreases

Engineering Contradiction:

Improvesurface hardnessVSAvoidadhesion

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent modifies the surface chemical parameters of the polyimide film through controlled thermal treatment and oxidation processes that increase surface energy and create anchoring sites, enabling strong adhesion of hard-coating layers without compromising the underlying film's optical properties

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a multi-layer composite structure where the polyimide base film is chemically bonded to the hard-coating layer through interface optimization, achieving both surface hardness and strong adhesion while maintaining low haze through careful control of layer thickness and interfacial compatibility

Inventive Principle:

Principle #40Composite materials

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 maintains excellent mechanical and optical properties under severe temperature conditions, enhancing the durability and reliability of display devices, particularly suitable for foldable and flexible displays, with improved folding characteristics and resistance to thermal fluctuations.

Implementation Method 1

polymerizing a diamine compound, a dianhydride compound, and a dicarbonyl compound in an organic solvent to prepare a polyamide-imide polymer solution

Methodology Applied

Scientific EffectPolymerization:

Implementation Method 2

thermally treating the gel sheet, wherein the thermal treatment of the gel sheet comprises hot air treatment in two or more steps

Methodology Applied

Scientific EffectThermal treatment: Heat Treatment

Data Source

PatentUS11873372B2Polyamide-imide film, preparation method thereof, and cover window comprising same

Publication Date: 2024.01.16 MICROWORKS SOLUTIONS CO LTD

AI summary

Embodiments relate to a polyamide-imide film that maintains its mechanical properties at least at a certain level under the conditions of high temperatures and low temperatures and is excellent in transparency and folding characteristics, a process for preparing the same, and a cover window comprising the same. The polyamide-imide film comprises a polyamide-imide polymer and has an MOR value defined in Equation 1a of 75% or more.