Photocurable Adhesive Sheet Layered Structure for Step Conformability
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Solution Overview
Problem
Adhesive sheets for image display devices face challenges in providing both step conformability and shape stability, especially when used with plastic protection panels under high-temperature and high-humidity conditions, where they can experience bubble formation, outgassing, and delamination.
Innovation Solution
A photocurable adhesive sheet with a layered structure comprising a first adhesive layer, a second adhesive layer, and an intermediate layer formed from a (meth)acrylic copolymer resin with a crosslinked structure, allowing for photocuring and maintaining shape stability and conformability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the flowability of the adhesive sheet is increased to improve step conformability, then the adhesive sheet can better conform to printed portions and steps, but the adhesive sheet becomes prone to glue overflow from the end of the adhesive sheet wound body or cut chip-processed article
Solution Approach 1:
The adhesive sheet is divided into multiple layers: a first adhesive layer, a second adhesive layer, and an intermediate layer. This segmentation allows each layer to have different properties - the outer adhesive layers provide flowability for step conformability, while the intermediate layer with crosslinked structure provides shape stability to prevent glue overflow.
Solution Approach 2:
Different regions of the adhesive sheet have different properties. The intermediate layer has a crosslinked structure that provides local rigidity and shape stability, while the outer adhesive layers maintain higher flowability for conforming to steps. This local differentiation resolves the contradiction between overall flowability and localized shape control.
2Manufacturing precision
If the adhesive sheet has high flowability to ensure complete filling of spaces, then the adhesive sheet can entirely fill the space conforming to printed portions, but the adhesive sheet may deform or lose shape stability
Solution Approach 1:
The adhesive sheet uses a composite structure with multiple layers having different material properties. The intermediate layer contains a crosslinked polymer structure that provides shape stability, while the outer adhesive layers contain uncured or partially cured adhesive material that provides flowability for complete space filling. This composite approach allows both high flowability and shape stability.
3Weight of moving object
If the adhesive sheet is used with plastic protection panels under high-temperature and high-humidity conditions, then the device can be lightweight and flexible, but bubbles may form near steps, outgas may be generated, and delamination may occur
Solution Approach 1:
The intermediate layer is pre-formed with a crosslinked structure before the adhesive layers are applied. This preliminary crosslinking creates a stable barrier layer that prevents outgassing and bubble formation under high-temperature and high-humidity conditions, ensuring reliability before the adhesive sheet is subjected to harsh environmental conditions.
Solution Approach 2:
The intermediate layer acts as an intermediary between the outer adhesive layers and the plastic protection panel. This intermediate layer with crosslinked structure mediates the interaction by providing a stable interface that prevents delamination and blocks outgas pathways, thereby improving reliability under harsh conditions while maintaining the lightweight plastic panel structure.
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 sheet achieves enhanced durability and cohesion through photocuring, while maintaining flexibility and conformability, preventing issues like glue overflow and delamination, and ensuring stability under varying conditions.
Implementation Method 1
a photocurable resin layer which is formed from a photocurable resin composition
Implementation Method 2
high flowability is required
Implementation Method 3
the intermediate layer is a layer that is formed from a resin composition containing a (meth)acrylic copolymer as a main component resin and has a crosslinked structure
Implementation Method 4
excellent in durability after attachment to an adherend member
Data Source
AI summary
A photocurable adhesive sheet may have both step conformability and shape stability and excellent in durability after attachment to an adhering member. Such a photocurable adhesive sheet may include a first adhesive layer, a second adhesive layer, and an intermediate layer interposed between the first and second adhesive layer. The intermediate layer may be a layer that is formed from a resin composition containing a (meth)acrylic copolymer as a main component resin and has a crosslinked structure. The first and/or second adhesive layer may be photocurable resin layers formed from a photocurable resin composition. The fall time in the measurement of holding force at 40° C. under a load of 1 N/cm2 may be 60 minutes or more, while the fall time in the measurement of holding force at 60° C. under a load of 1 N/cm2 may be less than 60 minutes.