Variable Hardness Pad for Curved Cover Glass Film Attachment
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Solution Overview
Problem
Attaching a film to a cover glass with multiple curvatures is challenging due to compressive and tensile deformations, leading to bubble defects and adhesive leakage, especially when the cover glass has all four sides curved, making it difficult to apply uniform pressure without damaging the film or leaking adhesive.
Innovation Solution
A pad with a flat portion and corner portions of varying hardness or thickness is used, where the corner portions have higher Shore Hardness (1.1 to 7 times greater) or protrude more than the flat portion, allowing for differential pressure application to securely attach the film to the cover glass without bubbles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If uniform pressure is applied to attach the film to the cover glass, then the film attachment process is simple, but adhesive leakage occurs and the film does not properly attach to curved surfaces
Solution Approach 1:
The pad is designed with different hardness values in different regions: the corner portions have higher hardness (1.1 to 7 times greater) than the flat portion. This local differentiation allows the pad to apply higher pressure to the corners of the cover glass where curvature creates attachment difficulties, while applying lower pressure to the flat central area to prevent adhesive leakage. This resolves the contradiction by making the pressure distribution non-uniform in a controlled manner that improves film attachment quality without complicating the overall attachment process.
2Reliability
If higher pressure is applied to corner portions to ensure proper film attachment, then bubble defects are prevented, but adhesive leakage occurs
Solution Approach 1:
The pad implements local quality differentiation by assigning higher hardness to corner portions and lower hardness to the flat portion. This allows the system to apply higher pressure locally at the corners to prevent bubble defects and ensure reliable film attachment, while simultaneously applying lower pressure to the central flat area to prevent adhesive leakage. The local quality approach resolves the contradiction by spatially separating the pressure requirements of different regions.
3Device complexity
If the pad has uniform hardness, then the pad structure is simple, but the film cannot be properly attached to cover glass with multiple curvatures
Solution Approach 1:
The pad structure incorporates local quality by varying the hardness of different portions: corner portions have higher hardness while the flat portion has lower hardness. This differentiation enables the pad to adapt to cover glass with multiple curvatures by applying appropriate pressure to each region, achieving precise film attachment. While this increases pad structure complexity compared to a uniform hardness design, it is the necessary compromise to achieve the required manufacturing precision for curved surfaces.
Solution Approach 2:
The pad design employs asymmetry by positioning harder material specifically at the corner portions rather than distributing it uniformly or symmetrically across the entire pad. This asymmetric hardness distribution matches the asymmetric pressure requirements of attaching film to curved cover glass surfaces, where corners require higher pressure than flat areas. The asymmetric design resolves the contradiction between structural simplicity and attachment precision.
Data Source
AI summary
An exemplary embodiment of the present inventive concept provides a pad including: a flat portion; and corner portions, wherein the corner portions may be positioned at four corners of the pad, and hardness of the corner portions may be greater than that of the flat portion.