Polyimide Window Cover Film for Foldable Displays
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Solution Overview
Problem
Current window cover films for flexible displays face challenges in maintaining mechanical strength, optical properties, and preventing fine cracks during repeated folding, which affects their durability and longevity.
Innovation Solution
A polyimide-based film with a hard coating layer is developed, featuring a micro flexural modulus of 15 to 40 GPa and micro flexural strength of 200 MPa or more, designed to withstand repeated bending without creasing or cracking, even after 200,000 cycles, ensuring excellent mechanical and optical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a glass film is used as window cover, then mechanical strength and optical properties are improved, but flexibility and ability to be folded are worsened
Solution Approach 1:
The patent replaces rigid glass films with flexible plastic films (polyimide, PET, PEN, PC) that can be folded and bent while maintaining protective functions. This enables the window cover to adapt to flexible and foldable display devices while preserving mechanical strength through careful material selection and thickness optimization.
Solution Approach 2:
The patent employs composite material structures combining multiple polymer layers with different properties to achieve both flexibility and mechanical strength. By selecting appropriate base materials and coating materials with complementary characteristics, the window cover film attains both foldability and durability required for flexible displays.
2Adaptability or versatility
If plastic film is used as window cover to provide flexibility, then adaptability is improved, but mechanical strength and resistance to fine cracks are worsened
Solution Approach 1:
The patent optimizes critical parameters including film thickness (5-50 μm), micro flexural modulus (15-40 GPa), and micro flexural strength (200 MPa or more) to achieve the desired balance between flexibility and mechanical strength. By carefully controlling these parameters, the plastic film maintains sufficient strength while remaining flexible enough for foldable applications.
Solution Approach 2:
The patent applies different material properties to different layers of the window cover structure. The base film provides flexibility while coating layers enhance surface hardness and crack resistance. This local differentiation of material qualities allows the overall structure to achieve both flexibility and mechanical strength.
3Adaptability or versatility
If plastic film is used as window cover to enable folding, then flexibility is improved, but durability under repeated bending is worsened
Solution Approach 1:
The patent specifies critical parameter ranges including micro flexural modulus of 15-40 GPa and micro flexural strength of 200 MPa or more to ensure the film can withstand repeated bending cycles without failure. These parameter optimizations directly address durability requirements for flexible displays undergoing frequent folding operations.
Solution Approach 2:
The patent uses composite structures with base films and coating layers where each component contributes specific properties. The multi-layer composite design enhances overall durability by distributing stress during bending and preventing crack propagation, thereby improving reliability under repeated mechanical cycling.
4Reliability
If high micro flexural modulus and strength are achieved to prevent cracks, then reliability is improved, but flexibility and pliability are worsened
Solution Approach 1:
The patent defines an optimal parameter window where micro flexural modulus is maintained between 15-40 GPa and micro flexural strength at 200 MPa or more. This parameter optimization ensures the film achieves sufficient crack resistance while maintaining the flexibility needed for foldable display applications, resolving the trade-off between reliability and adaptability.
Data Source
AI summary
Provided are a window cover film and a flexible display panel including the same. More preferably, a window cover film including a transparent film and a hard coating layer and a flexible display panel including the same are provided.