Foldable Window Layer Stack for Impact-Resistant Flexible Displays
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Solution Overview
Problem
Bendable or foldable electronic apparatuses face a trade-off between improved reliability against bending stress and deteriorated reliability against external impacts.
Innovation Solution
A foldable electronic apparatus design featuring a window member with a first hard film, a soft film, and a second hard film, where the soft film has a lower modulus than the first hard film and a higher recovery rate, and the second hard film has a higher modulus than the soft film, with specific thicknesses and moduli to enhance impact resistance and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the window member uses a single hard film structure, then impact resistance is improved, but flexibility and resistance to bending stress deteriorate
Solution Approach 1:
The window member is segmented into multiple functional layers: a first hard film (75μm) for impact resistance, a soft film (50-150μm) for flexibility and bending stress resistance, and a second hard film (30-75μm) for additional protection. This segmentation allows each layer to perform its specific function optimally, resolving the contradiction between impact resistance and flexibility.
Solution Approach 2:
The window member uses a composite structure combining hard films (resin or glass) and soft films with different moduli. The soft film has a modulus lower than the first hard film and higher than the second hard film, creating a composite material system that simultaneously provides impact resistance, flexibility, and bending stress resistance.
2Reliability
If the window member uses a single soft film structure, then flexibility is improved, but impact resistance deteriorates
Solution Approach 1:
The protective function is segmented between multiple hard films and one soft film. The soft film handles flexibility and bending stress, while the first and second hard films handle impact resistance. This segmentation prevents any single layer from being overloaded with conflicting requirements.
Solution Approach 2:
The composite structure combines the flexibility of the soft film with the impact resistance of the hard films. The specific modulus relationships (soft film modulus < first hard film modulus and soft film modulus > second hard film modulus) create a balanced composite that achieves both flexibility and impact resistance.
3Strength
If the window member thickness is increased, then impact resistance is improved, but folding properties and device complexity deteriorate
Solution Approach 1:
Different regions of the window member have different properties optimized for different functions. The first hard film (75μm) provides impact resistance, the soft film (50-150μm) provides flexibility, and the second hard film (30-75μm) provides additional protection. This local quality differentiation allows the overall structure to be thin enough for folding while providing sufficient impact resistance.
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 design provides improved impact resistance and flexibility, ensuring stable protection of the electronic panel during folding and external impacts, while maintaining optimal folding properties and reducing defects like de-lamination and buckling.
Implementation Method 1
a soft film disposed between the first hard film and the electronic panel and having a modulus lower than a modulus of the first hard film... the soft film has a recovery rate of about 90% or more
Implementation Method 2
the soft film and the second soft film may be bonded with an adhesive layer between the soft film and the second soft film
Data Source
AI summary
Provided is an electronic apparatus including an electronic panel including a light-emitting element and foldable with respect to a folding axis extending along a first direction, and a window member disposed on the electronic panel and foldable with respect to the folding axis. The window member includes a first hard film disposed on an uppermost part, a soft film disposed between the first hard film and the electronic panel and having a modulus lower than a modulus of the first hard film, and a second hard film disposed between the first hard film and the electronic panel and having a modulus higher than a modulus of the soft film. The soft film has a recovery rate of about 90% or more.