Segmented Barrier Adhesive for Foldable Display Stress Control
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Solution Overview
Problem
Existing flexible electronic devices face challenges in maintaining product reliability and structural integrity, particularly in foldable areas, due to issues with stress concentration and material fatigue during folding and unfolding.
Innovation Solution
A display device design incorporating a support layer with barrier and cushion layers, where the cushion layer has a lower elastic modulus than the support layer, and a barrier adhesive layer with specific spacing and thickness configurations, to distribute stress and enhance structural stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a continuous barrier adhesive layer is used across the support layer, then adhesion strength is improved, but stress concentration increases at the folding area
Solution Approach 1:
The barrier adhesive layer is divided into multiple discrete adhesive portions (first adhesive portion, second adhesive portion, third adhesive portion) positioned at specific locations on the support layer. This segmentation allows the adhesive to maintain bonding strength at non-folding areas while avoiding continuous adhesion across the folding area, thereby reducing stress concentration during bending operations.
Solution Approach 2:
Different regions of the support layer have different adhesive characteristics: the barrier adhesive layer provides strong adhesion at non-folding areas (first, second, and third adhesive portions) while being absent or reduced at the folding area. This local differentiation optimizes both adhesion strength where needed and stress distribution during folding.
2Strength
If the barrier adhesive layer has large thickness, then bonding strength is improved, but flexibility and stress distribution are reduced
Solution Approach 1:
The thickness of the barrier adhesive layer is precisely controlled within the range of 1 μm to 10 μm. This parameter optimization ensures sufficient bonding strength while maintaining adequate flexibility for the folding operation. The thin-film characteristic allows the adhesive to conform to curvature changes without generating excessive stress.
3Reliability
If the cushion layer extends to the folding area, then protection is improved, but stress concentration increases
Solution Approach 1:
The cushion layer is segmented into a first cushion layer and a second cushion layer separated by a gap that corresponds to the folding area. This segmentation allows the cushioning material to protect the support layer at non-folding areas while the gap prevents stress concentration at the folding area where bending occurs.
Solution Approach 2:
The cushion layer is extracted or removed from the folding area, creating a gap between the first and second cushion layers. This extraction eliminates the source of stress concentration while maintaining cushioning protection at the non-folding areas where mechanical impact needs to be absorbed.
4Stability of the object's composition
If the support layer has high elastic modulus, then structural stability is improved, but flexibility and stress distribution are reduced
Solution Approach 1:
The support layer exhibits different mechanical properties in different regions: the non-folding areas maintain high elastic modulus for structural stability and rigidity, while the folding area has reduced elastic modulus to enable flexibility and stress distribution during bending. This local quality differentiation resolves the contradiction between overall stability and local flexibility.
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 improves product reliability by reducing stress concentration and material fatigue, ensuring consistent performance and longevity of foldable electronic devices.
Implementation Method 1
the cushion layer has a lower elastic modulus than the support layer
Implementation Method 2
distribute stress and enhance structural stability
Implementation Method 3
a barrier adhesive layer between the barrier layer and the support layer
Data Source
AI summary
A display device including a display panel including a folding area and a non-folding area adjacent along a first direction, a support layer facing the display panel with a barrier layer therebetween, openings defined in the support layer and corresponding to the folding area, a cushion layer facing the display panel with the support layer therebetween, and a barrier adhesive layer between the barrier layer and the support layer, the barrier adhesive layer including a first barrier portion and a second barrier portion spaced apart from each other along the first direction with the plurality of openings of the support layer therebetween.