Cover Window Coating Thickness Distribution for Bend Crack Prevention
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Solution Overview
Problem
Display devices, especially flexible and bendable ones, face challenges in preventing crack initiation in bending areas and maintaining rigidity in flat areas due to restoration forces, which existing cover windows are unable to effectively address.
Innovation Solution
A cover window design with a base layer and a coating layer of varying thicknesses, where the coating layer is thicker on flat portions and thinner on bending portions, and an auxiliary coating layer is applied only on flat portions, enhancing the rigidity of the flat areas and reducing crack initiation by managing restoration forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the coating layer has uniform thickness across the entire cover window, then the manufacturing process is simple, but the flat area lacks sufficient rigidity and the bending area is prone to crack initiation
Solution Approach 1:
The coating layer is designed with different thicknesses in different regions: a first coating portion with greater thickness on the flat area to enhance rigidity, and a second coating portion with lesser thickness on the bending area to reduce restoration forces and prevent crack initiation. This local differentiation resolves the contradiction by providing enhanced rigidity where needed without compromising flexibility in bending regions.
2Reliability
If the coating layer is thicker on the bending portion to prevent cracks, then crack initiation is reduced, but the restoration force increases causing damage to the display module
Solution Approach 1:
The coating layer thickness is locally optimized: the second coating portion on the bending area has lesser thickness compared to a uniform thick coating, which reduces the restoration force exerted on the display module during bending while still providing sufficient protection against crack initiation. This resolves the contradiction between crack prevention and force reduction.
3Reliability
If an auxiliary coating layer is applied on the bending area, then crack prevention is enhanced, but the restoration force and complexity increase
Solution Approach 1:
The auxiliary coating layer is selectively applied only on the flat area (first coating portion) rather than the entire cover window. This extraction approach provides enhanced crack prevention and rigidity where most needed while avoiding unnecessary complexity and restoration forces on the bending area, resolving the contradiction between reliability enhancement and complexity increase.
4Strength
If the coating layer has varying thickness to optimize performance, then rigidity and crack prevention are improved, but the manufacturing precision requirements increase
Solution Approach 1:
The coating layer is designed with two distinct thickness regions (first coating portion with greater thickness and second coating portion with lesser thickness) that can be manufactured using conventional techniques. The clear differentiation between regions allows for controlled manufacturing while achieving optimized structural performance, balancing the contradiction between strength enhancement and manufacturing precision requirements.
Data Source
AI summary
A cover window includes a base layer including a first flat portion and a first bending portion bent from a first end of the first flat portion and a coating layer including a first coating portion disposed on the first flat portion and a second coating portion disposed on the first bending portion and having a thickness less than a thickness of the first coating portion. A first end of the second coating portion has a thickness greater than a thickness of a second end of the second coating portion, and the first end of the second coating portion is closer to the first coating portion than the second end of the second coating portion is.