Foldable Cover Window Adhesion Zoning for Rework and Folding
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Solution Overview
Problem
Existing foldable display devices face challenges in maintaining folding characteristics while facilitating rework of the cover window due to issues with adhesive strength and peeling during repetitive folding.
Innovation Solution
A cover window design featuring a protective film with symmetrical protrusions and varying adhesive strengths across different areas to enhance folding characteristics and enable easy rework, using a substrate layer, hard-coating layer, and adhesive layers with tailored adhesion properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If adhesive strength is increased to prevent peeling during folding, then folding characteristics are improved, but rework becomes difficult
Solution Approach 1:
The adhesive layer is divided into multiple regions with different adhesive strengths: a first adhesive region with stronger adhesion for peeling resistance during folding, and a second adhesive region with weaker adhesion for easy rework. This segmentation allows the same adhesive layer to satisfy both contradictory requirements of reliability and ease of repair in different spatial zones.
Solution Approach 2:
Different portions of the adhesive layer are assigned different adhesive strength properties. The first adhesive region (closer to the center) has higher adhesive strength to prevent peeling during folding operations, while the second adhesive region (closer to the edges) has lower adhesive strength to facilitate easy removal and rework. This local differentiation resolves the contradiction between maintaining folding reliability and enabling ease of repair.
2Ease of manufacture
If uniform adhesive strength is used across the protective film, then manufacturing is simplified, but peeling occurs during repetitive folding
Solution Approach 1:
The adhesive layer transitions from uniform to non-uniform with locally differentiated adhesive strengths. The first adhesive region has higher adhesive strength positioned centrally to prevent peeling during folding, while the second adhesive region has lower adhesive strength at the edges. This local quality differentiation maintains manufacturing feasibility while significantly improving peeling resistance during repetitive folding operations.
3Ease of repair
If adhesive strength is decreased to facilitate rework, then ease of repair is improved, but folding characteristics deteriorate due to peeling
Solution Approach 1:
The adhesive layer is segmented into a first adhesive region with stronger adhesion for maintaining folding characteristics and a second adhesive region with weaker adhesion for facilitating rework. By spatially separating these conflicting functional requirements into different regions, the design achieves both reliable folding performance and ease of repair without compromise.
Solution Approach 2:
The adhesive strength parameter is varied across different regions of the adhesive layer. The first adhesive region maintains higher adhesive strength parameters to prevent peeling during folding, while the second adhesive region uses lower adhesive strength parameters to enable easy removal. This parameter differentiation allows simultaneous satisfaction of both folding reliability and repair ease requirements.
Data Source
AI summary
Provided is a cover window. The cover window includes a substrate layer. The cover window further includes a hard-coating layer on the substrate layer. The cover window further includes a protective film disposed on the hard-coating layer and including a base film and a plurality of protrusions protruding from the base film. The cover window further includes an adhesive layer disposed on surfaces of the plurality of protrusions and bonding the hard-coating layer and the protective film. The protective film includes a first area and second areas disposed on both sides of the first area. The plurality of protrusions are disposed in the first area. The plurality of protrusions have a shape in which the protrusions disposed on one side and the protrusions disposed on the other side are symmetrical to each other with respect to a central line of the first area.