Gradient Elastic Modulus Window Coating for Flexible Display Delamination
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Solution Overview
Problem
Flexible display devices face challenges with delamination issues during bending due to differences in elastic modulus between the display panel and the window coating layer, leading to reduced durability and portability.
Innovation Solution
A window coating layer with a non-vanishing elastic modulus gradient, comprising multiple regions with varying elastic moduli, is applied directly onto the display panel, ensuring high flexibility and durability by preventing interlayer delamination and surface deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a window coating layer with uniform elastic modulus is applied on the display panel, then the manufacturing process is simple, but delamination occurs during bending due to elastic modulus mismatch
Solution Approach 1:
The window coating layer is designed with a non-uniform elastic modulus distribution, where the elastic modulus increases from the lower surface (in contact with display panel) to the upper surface. This gradient structure allows the lower region to maintain better adhesion to the display panel while the upper region provides sufficient mechanical strength, thereby preventing delamination during bending without complicating the manufacturing process.
Solution Approach 2:
The elastic modulus parameter of the window coating layer is changed continuously from the lower surface to the upper surface, creating a gradient material property. This parameter change enables the coating layer to adapt to different mechanical requirements at different depths, resolving the contradiction between adhesion and structural integrity during bending operations.
2Strength
If the window coating layer has high elastic modulus throughout, then durability is improved, but delamination occurs during bending due to stress concentration
Solution Approach 1:
Different regions of the window coating layer are assigned different elastic modulus values to fulfill different functions. The lower region has lower elastic modulus to maintain flexibility and adhesion to the display panel, while the upper region has higher elastic modulus to provide durability and resistance to external impacts, thus avoiding stress concentration and delamination during bending.
Solution Approach 2:
The window coating layer is designed as a composite structure with varying material composition to achieve a gradient elastic modulus. This composite approach allows combining materials with different mechanical properties in a controlled manner, providing both adhesion to the display panel and sufficient durability against external forces without causing delamination.
3Reliability
If a multi-layer window coating structure is used to prevent delamination, then adhesion is improved, but device complexity increases
Solution Approach 1:
Instead of using multiple discrete layers with different materials, the invention achieves the effect of a multi-layer structure by continuously changing the elastic modulus parameter within a single coating layer. This gradient approach maintains the adhesion benefits of multi-layer structures while avoiding the complexity of manufacturing and aligning multiple distinct layers.
Data Source
AI summary
A display device includes a display panel and a window coating layer disposed directly on an upper surface of the display panel. The window coating layer includes a first region which has an increasing elastic modulus in a direction from the display panel toward the window coating layer.