Foldable Display Layer Structure to Prevent Bending-Area Cracks
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Solution Overview
Problem
Foldable display devices face issues with cracks or damage in the bending protective layer due to slipping of the polarizing layer when pressure is applied during folding, leading to potential structural failure.
Innovation Solution
The implementation of a bending protective layer with a low modulus material, such as urethane acrylate or acrylate, and a specific adhesive layer configuration to prevent the polarizing layer from slipping and applying pressure, thereby reducing the likelihood of cracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a rigid protective layer is used to protect the display device, then structural strength is improved, but cracks occur in the bending protective layer when the polarizing layer slips and pressure is applied during folding
Solution Approach 1:
The patent applies parameter changes by selecting a bending protective layer material with a specific modulus range (0.1 GPa to 10 GPa), which is significantly lower than conventional rigid protective materials. This parameter adjustment allows the layer to deform elastically during folding without cracking, while still providing adequate protection against minor impacts and scratches.
Solution Approach 2:
The patent employs composite materials by combining the bending protective layer made of low-modulus material with other display layers including the polarizing layer, adhesive layers, and rigid protective layers in different regions. This composite structure allows each layer to perform its specific function - the bending protective layer handles flexural stress while other layers provide structural support and protection.
2Adaptability or versatility
If the polarizing layer is allowed to slip during folding, then flexibility is improved, but pressure is applied to the bending protective layer causing cracks
Solution Approach 1:
The patent changes the mechanical parameter of the bending protective layer by using material with low modulus (0.1 GPa to 10 GPa), enabling it to accommodate the pressure generated by polarizing layer slippage during folding without cracking. The low modulus allows elastic deformation that absorbs the stress from polarizing layer movement.
Solution Approach 2:
The bending protective layer acts as an intermediary between the polarizing layer and the rigid protective layer. It mediates the stress transfer by deforming elastically when the polarizing layer slips, preventing direct transmission of concentrated pressure to any single point, thereby avoiding crack formation.
3Reliability
If a low modulus material is used for the bending protective layer, then crack resistance is improved, but structural strength is reduced
Solution Approach 1:
The patent optimizes the modulus parameter to a specific range (0.1 GPa to 10 GPa) that balances crack resistance and structural strength. This parameter selection ensures the material is soft enough to prevent cracks during folding while maintaining sufficient strength to provide protective functionality against minor impacts and environmental factors.
Solution Approach 2:
The patent applies local quality by using the low-modulus bending protective layer specifically in the bending area where flexural stress occurs, while other regions of the display device can use rigid protective layers for maximum protection. This localized application ensures crack resistance where needed without unnecessarily reducing overall structural strength.
Data Source
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AI summary
A foldable display device includes a display panel including a first non-folding area including a bending area and a non-bending area, a folding area connected to the first non-folding area, and a second non-folding area spaced apart from the first non-folding area by the folding area, an adhesive layer disposed on the non-bending area of the display panel and having a first height in a direction perpendicular to a main plane extension direction of the display panel, a polarizing layer disposed on the adhesive layer and a bending protective layer disposed on the bending area of the display panel and having a second height, in the direction, lower than the first height.