Optically Clear Adhesive Copolymer for Plastic Bonding
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Solution Overview
Problem
Optically clear adhesives (OCAs) used in optical laminates face challenges in maintaining transparency and preventing bubbling, peeling, clouding, or white opacity under high temperature and high humidity conditions, especially when used with plastic panels like PMMA or polycarbonates, and can cause corrosion in electrically conductive layers.
Innovation Solution
An optically clear adhesive comprising a copolymer with 25 to 80 parts by mass of alkyl (meth)acrylate, 15 to 50 parts by mass of hydroxyl group-containing monomer, and 5 to 25 parts by mass of a macromer with a glass transition temperature of 50° C. or higher, which contains substantially no acidic groups, ensuring excellent heat resistance and resistance to moist heat while preventing corrosion of conductive layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional OCAs are used to bond plastic panels, then bonding is achieved, but bubbling and peeling occur under high temperature conditions due to outgas from plastic materials
Solution Approach 1:
The patent changes the chemical composition parameters of the OCA by incorporating specific functional monomers (hydroxyl group-containing monomers and carboxyl group-containing monomers) in controlled amounts. This compositional modification enables the adhesive to resist outgas from plastic panels under high temperature, preventing bubbling and peeling while maintaining bonding durability.
Solution Approach 2:
The patent creates a composite adhesive system by combining multiple monomer types (alkyl (meth)acrylate, hydroxyl group-containing monomer, carboxyl group-containing monomer) in specific ratios. This composite composition provides synergistic effects that enhance resistance to both outgas and moisture vapor, solving the bubbling and peeling problem.
2Reliability
If OCAs are used in touch panels with electrically conductive layers, then bonding is achieved, but corrosion of conductive layers occurs due to acidic components in the adhesive
Solution Approach 1:
The patent carefully controls the pH and acidic component content by selecting specific carboxyl group-containing monomers and limiting their concentration (0.1-10 parts by mass). This parameter control reduces acidity to levels that prevent corrosion of electrically conductive layers while maintaining adequate bonding performance.
Solution Approach 2:
The patent uses hydroxyl group-containing monomers as intermediary components that can neutralize or buffer the acidic effects of carboxyl group-containing monomers. This intermediary action protects the conductive layers from corrosion while the carboxyl groups provide necessary adhesion to the plastic panels.
3Ease of manufacture
If OCAs are used to bond cover lenses to touch panel modules, then assembly is achieved, but clouding or white opacity occurs under moist heat conditions
Solution Approach 1:
The patent modifies the adhesive composition by incorporating hydroxyl group-containing monomers (15-50 parts by mass) that provide resistance to moisture vapor. This compositional change prevents clouding and white opacity under moist heat conditions while maintaining the assembly capability of the touch panel module.
Solution Approach 2:
The patent uses a relatively simple monomer composition that can be easily applied and cured, providing a cost-effective solution that prevents optical degradation without requiring complex multi-layer adhesive systems.
4Weight of moving object
If plastic panels are used for touch panel modules, then lightweight and flexible properties are achieved, but both the panels and cover lenses generate outgas under high temperature
Solution Approach 1:
The patent uses the OCA as an intermediary material between the plastic panel and cover lens that can withstand outgas from both components. The adhesive's specific composition (hydroxyl and carboxyl group-containing monomers) provides resistance to outgas, preventing bubbling and peeling while allowing the use of lightweight plastic materials.
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 provides excellent heat resistance and resistance to moist heat, preventing bubbling, peeling, and clouding, while maintaining optical transparency and avoiding corrosion of electrically conductive layers, suitable for harsh environments such as automotive touch panels and optical displays.
Implementation Method 1
a copolymer of a monomer mixture containing approximately 25 to approximately 80 parts by mass of an alkyl (meth)acrylate, approximately 15 to approximately 50 parts by mass of a hydroxyl group-containing monomer, and approximately 5 to approximately 25 parts by mass of a macromer
Implementation Method 2
approximately 15 to approximately 50 parts by mass of a hydroxyl group-containing monomer
Data Source
AI summary
The present invention is a copolymer of a monomer mixture including about 25 to about 80 parts by mass of an alkyl (meth)acrylate, approximately 15 to approximately 50 parts by mass of a hydroxyl group-containing monomer, and approximately 5 to approximately 25 parts by mass of a macromer having a glass transition temperature (Tg) of approximately 50° C. or higher. The copolymer contains substantially no acidic groups.