Thin PSA Sheet With Coating Layer for Air Release
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Solution Overview
Problem
PSA sheets used in mobile electronics face challenges with air bubbles forming between the sheet and the adherend, which degrade adhesive properties and appearance, especially with the thinning of PSA sheets, where air release properties are impaired due to limited groove depth in the PSA layer.
Innovation Solution
A PSA sheet with a substrate film and a PSA layer, where the PSA layer has a thickness of 20 μm or less and a coating layer with a thickness less than 3 μm, providing good air release properties and maintaining adhesive strength, even at early stages of application, by ensuring the coating layer's thickness is suitably proportioned relative to the PSA layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the PSA layer is thinned to reduce size and weight, then the PSA sheet becomes suitable for mobile electronics, but the air release properties are impaired due to limited groove depth
Solution Approach 1:
The invention introduces a coating layer with specific properties (different from the PSA layer) that provides air release functionality. This coating layer is applied locally to the PSA layer surface, creating a specialized region for air elimination without requiring the entire PSA layer to be thick. The coating layer's specific composition and structure enable effective air release even when the overall PSA layer thickness is reduced to 20 μm or less.
2Reliability
If grooves are formed in the PSA layer surface to eliminate air, then air release properties improve, but the grooves fade or are lost due to PSA layer viscoelasticity when thickness is reduced
Solution Approach 1:
The invention separates the air release function from the PSA layer itself by introducing a distinct coating layer. Instead of relying on grooves formed in the PSA layer (which fade due to viscoelasticity), the coating layer is applied as a separate entity that maintains its structural integrity. This segmentation allows the coating layer to provide stable air release channels without being affected by the PSA layer's viscoelastic deformation.
Solution Approach 2:
The invention creates a composite structure consisting of the PSA layer and the coating layer. The coating layer is formulated with different material properties than the PSA layer, specifically designed to maintain stable air release channels. This composite material approach allows the coating layer to resist the viscoelastic effects that cause groove fading in conventional single-layer PSA sheets.
3Reliability
If a coating layer is applied to the PSA layer surface, then air release properties improve, but the smoothness of the adhesive face may be degraded
Solution Approach 1:
The invention carefully controls the thickness parameter of the coating layer to optimize the balance between air release properties and adhesive face smoothness. By limiting the coating layer thickness to a specific range, the invention ensures that the coating provides sufficient air release channels while maintaining enough smoothness for effective adhesion. This parameter optimization resolves the contradiction between needing surface irregularities for air release and surface smoothness for bonding.
Data Source
AI summary
Provided is a PSA sheet capable of bringing about good air release properties in mobile electronic applications. The present invention provides a PSA sheet for mobile electronics. The PSA sheet comprises a substrate film and a PSA layer provided to at least one face of the substrate film. The PSA layer has a thickness of 20 μm or less. The PSA sheet further comprises a coating layer that partially covers the PSA layer surface. The coating layer has a thickness less than 3 μm.