Polyimide Film Modulus Control for Foldable Display Durability
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Solution Overview
Problem
Polyimide-based films used in foldable and flexible displays suffer from deteriorated mechanical properties upon repeated folding or elongation/shrinkage, leading to deformation and non-uniform screen states when a load is applied, which affects their optical and mechanical performance.
Innovation Solution
A polymer film comprising a polyamide-based or polyimide-based resin with specific modulus retention and thermal treatment conditions to maintain mechanical properties and transparency, characterized by MOR0/9 ≤ 2% and S1, S2, S3 ≤ 40%, 55%, and 80% respectively, ensuring minimal deformation under load and excellent folding characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyimide-based film is used for foldable displays, then heat resistance and chemical resistance are improved, but mechanical properties deteriorate after repeated folding or elongation/shrinkage
Solution Approach 1:
The patent applies parameter changes by controlling the modulus ratio MOR0/9 to 2% or less and the deformation ratios S1, S2, and S3 to specific ranges (40%, 55%, and 80% respectively). These parameter specifications ensure that the polyimide-based film maintains its mechanical properties after repeated folding while preserving its heat and chemical resistance characteristics.
2Adaptability or versatility
If polyimide-based film is applied to foldable displays, then flexibility is improved, but deformation occurs when load is continuously applied
Solution Approach 1:
The patent resolves this contradiction by specifying parameter ranges for deformation control: S1 ≤ 40%, S2 ≤ 55%, and S3 ≤ 80%. These parameters define the acceptable deformation limits under continuous load, allowing the film to remain flexible for folding applications while preventing excessive deformation that would cause screen distortion.
3Reliability
If additives are introduced to improve mechanical properties, then durability after repeated folding is improved, but optical properties or compatibility are impaired
Solution Approach 1:
The patent resolves this contradiction by establishing a durability criterion of MOR0/9 ≤ 2% that can be achieved through compositional adjustments and processing optimization rather than by adding optical interfering substances. This parameter-based approach allows improving durability while preserving optical properties.
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 polymer film maintains excellent mechanical and optical properties, preventing deformation under continuous load and ensuring a uniform screen state, suitable for foldable and flexible displays with improved durability and flexibility.
Implementation Method 1
maintains excellent mechanical properties even after repeated elongation and shrinkage in the elastic region
Implementation Method 2
A polymer film comprising a polyamide-based or polyimide-based resin with specific modulus retention and thermal treatment conditions
Data Source
AI summary
Embodiments relate to a polymer film that is excellent in folding characteristics and transparency and maintains excellent mechanical properties even after repeated elongation and shrinkage in the elastic region, a process for preparing the same, and a front panel and a display device comprising the same. The polymer film comprises a polymer resin selected from the group consisting of a polyamide-based resin and a polyimide-based resin and has an MOR0/9 of Equation A of 2% or less.