Epoxy-Functionalized Polyacrylate Adhesive for Moisture Barrier
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Solution Overview
Problem
Current water vapor barrier adhesive compositions for encapsulating moisture-sensitive electronic structures, such as OLEDs, face challenges with high epoxy content leading to processing issues like 'squeezing-out' due to liquid epoxy resins and require refrigerated transport for b-staged epoxy systems, while polar materials like poly(meth)acrylates exhibit low water vapor barrier performance.
Innovation Solution
A curable adhesive composition comprising a (co)poly(meth)acrylate functionalized with epoxy groups, specifically cycloaliphatic epoxy groups, with a weight-average molar mass between 5000 g/mol and 20,000 g/mol, combined with a curing agent for thermal or UV-induced curing, offering improved viscosity and adhesion without the need for refrigerated transport.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high epoxy content is used to improve water vapor barrier performance, then barrier performance increases, but processing characteristics deteriorate due to squeezing-out
Solution Approach 1:
The invention changes the physical state parameter of the epoxy resin from liquid to solid by using pre-polymerized or partially crosslinked epoxy resins. This parameter change allows high epoxy content (improving barrier performance) while eliminating the squeezing-out issue that plagues liquid epoxy systems during bonding processes.
Solution Approach 2:
The invention creates a composite adhesive system combining solid epoxy resin particles or pre-polymerized epoxy networks with adhesive polymers and tackifying resins. This composite approach maintains the water vapor barrier benefits of high epoxy content while the polymer matrix provides cohesive strength and prevents processing defects like squeezing-out.
2Ease of operation
If b-staged epoxy systems are used to avoid refrigerated transport, then ease of operation improves, but device complexity increases due to crosslinking control requirements
Solution Approach 1:
The invention performs preliminary polymerization or partial crosslinking of the epoxy resin before final application. This preliminary action creates a pre-polymerized or partially crosslinked epoxy resin that can be stored and transported at ambient conditions without requiring refrigeration, while still maintaining reactivity for final curing.
Solution Approach 2:
The invention uses partially crosslinked epoxy resins where the crosslinking process is intentionally stopped at an intermediate stage. This partial action provides sufficient stability for ambient storage and handling while retaining enough reactive groups to complete crosslinking during the bonding process, avoiding the need for full pre-crosslinking that would eliminate reactivity.
3Strength
If poly(meth)acrylates are used to improve adhesion, then adhesion performance improves, but water vapor barrier performance deteriorates
Solution Approach 1:
The invention creates a composite system where poly(meth)acrylate polymers provide adhesion to substrates while solid epoxy resin particles or pre-polymerized epoxy networks provide the water vapor barrier function. The synergistic combination allows both adhesion and barrier performance to be achieved simultaneously, overcoming the limitation of pure poly(meth)acrylate systems.
Solution Approach 2:
The invention assigns different functional qualities to different components of the adhesive system: the poly(meth)acrylate polymer matrix provides adhesion and flexibility at the interface with substrates, while the dispersed epoxy resin particles or phases provide the water vapor barrier properties in the bulk adhesive layer. This local differentiation of functions allows both requirements to be met.
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
The adhesive composition provides a robust water vapor barrier with a lag time of at least 150 hours, ensuring effective sealing of sensitive electronic components while maintaining adaptability and preventing 'squeezing-out' during bonding.
Implementation Method 1
A curable adhesive composition comprising a (co)poly(meth)acrylate functionalized with epoxy groups, specifically cycloaliphatic epoxy groups, with a weight-average molar mass between 5000 g/mol and 20,000 g/mol, combined with a curing agent for thermal or UV-induced curing
Implementation Method 2
The adhesive composition provides a robust water vapor barrier with a lag time of at least 150 hours, ensuring effective sealing of sensitive electronic components
Data Source
AI summary
Single- or double-sided adhesive tapes and methods at least partly encapsulate an (opto)electronic structure. The tapes and method include a carrier and at least one layer of a curable adhesive composition having the following components: (A) 20% to 99.9% by weight (based on the entirety of the curable adhesive composition) of a (co)polymer functionalized with epoxy groups and having a weight-average molar mass of at least 5000 g/mol, based on more than 30% to 100% by weight, (based on the entirety of the parent monomers of the epoxy-functionalized (co)polymer) of at least one type of (meth)acrylic (co)monomer (a) functionalized with an epoxy group; and (B) 0.1% to 5% by weight (based on the entirety of the curable adhesive composition) of at least one curing agent configured to induce curing of the (co)polymer (A) with reaction of its epoxy groups by thermal means and/or by supply of UV radiation.