Embossing Crosslinked Pressure Sensitive Adhesive for Optical Clarity
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Solution Overview
Problem
Microstructured adhesive articles face defects due to stresses introduced during lamination, which affect their optical properties as they try to return to their initial microstructured state from a planar final state.
Innovation Solution
Embossing a crosslinked pressure sensitive adhesive layer to create a microstructured surface that remains substantially planar in both states, minimizing stress and using a microstructured release liner or molding tool to achieve this.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a flowable adhesive is coated onto a microstructured release liner or molding tool, then the adhesive surface becomes microstructured to allow air escape during lamination, but stresses are introduced into the adhesive as it relaxes and tries to return to its initial microstructured state, creating defects that adversely affect optical properties
Solution Approach 1:
The patent inverts the conventional approach by embossing the adhesive surface to create microstructured features rather than relying on the adhesive to naturally return to a microstructured state. This inversion resolves the contradiction by eliminating the stress relaxation problem while maintaining the air escape functionality needed for reliable bonding.
Solution Approach 2:
The patent changes the physical state of the adhesive from flowable to crosslinked before embossing. This parameter change allows the adhesive to maintain its microstructured configuration without the stress relaxation that occurs in flowable adhesives, thereby preserving optical properties while ensuring reliable bonding.
2Stability of the object's composition
If the adhesive is crosslinked before embossing, then the microstructured surface remains stable and planar in both initial and final states, minimizing stress formation, but the process requires additional embossing equipment and steps
Solution Approach 1:
The patent applies preliminary crosslinking to the adhesive before embossing. This preliminary action stabilizes the adhesive structure, allowing it to maintain the microconfigured state without stress relaxation, thereby reducing the need for complex equipment to maintain structural integrity during the lamination process.
3Object-generated harmful factors
If microstructured features are created in the adhesive surface, then air can escape from the bonding interface to minimize bubbles and pinholes, but the microstructural features flatten out during lamination and introduce stresses as the adhesive tries to return to its initial state
Solution Approach 1:
The patent changes the adhesive from flowable to crosslinked state before embossing. This parameter change eliminates the stress relaxation that causes harmful internal stresses, while the embossed microstructured features continue to provide air escape pathways to prevent bubble and pinhole formation during lamination.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method reduces stress-related defects and maintains low haze and high luminous transmittance, making the adhesive suitable for optical applications by ensuring the adhesive surface remains stable and effectively bonds with substrates.
Implementation Method 1
embossing the surface of the crosslinked pressure sensitive adhesive layer to form a crosslinked pressure sensitive adhesive layer having a microstructured adhesive surface
Implementation Method 2
the microstructural features created in the adhesive surface allow air to escape from the bonding interface, thereby minimizing or preventing the formation of bubbles and pinholes
Implementation Method 3
the microstructural features flatten out and wet the substrate surface under the influence of applied pressure
Data Source
AI summary
A method of making a microstructured adhesive article that includes (a) providing an article comprising a crosslinked pressure sensitive adhesive layer disposed on a backing; and (b) embossing the surface of the crosslinked pressure sensitive adhesive layer to form a crosslinked pressure sensitive adhesive layer having a microstructured adhesive surface.