SIS Block Copolymer Adhesive Refractive Index Matching
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Solution Overview
Problem
Existing adhesive compositions face challenges in achieving optimal adhesion, cohesive strength, and refractive index matching for applications such as pressure-sensitive adhesives and optical coatings, particularly when applied to transparent substrates or conductive traces, due to limitations in the properties of conventional block copolymers like SIS.
Innovation Solution
The development of compositions comprising at least 20 wt.% block copolymer with polyvinyl aromatic end blocks and a polyisoprene midblock, combined with ethylenically unsaturated monomers like (meth)acryl or vinyl ether, which can be cured to enhance adhesion and refractive index, thereby improving the adhesive's performance on various substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional SIS block copolymer is used as adhesive, then the adhesive composition has good basic adhesion properties, but the refractive index cannot be adequately adjusted and cohesive strength is insufficient
Solution Approach 1:
The patent changes the chemical composition parameters of the adhesive by incorporating ethylenically unsaturated monomers with specific Log P values (at least 2.2) and aromatic content (at least 20 wt.%). This allows adjustment of the refractive index to match transparent substrates while simultaneously improving cohesive strength through the curing reaction of the unsaturated monomers.
Solution Approach 2:
The patent creates a composite adhesive system combining SIS block copolymer (for basic adhesion), ethylenically unsaturated monomers (for refractive index adjustment and curing), and optional aromatic monomers (for enhanced optical properties). This composite approach allows each component to contribute its specific properties, resolving the contradiction between cohesive strength and refractive index adjustability.
2Strength
If the adhesive is cured to enhance adhesion, then bonding strength improves, but the processing flexibility and application window are reduced
Solution Approach 1:
The patent employs a dynamic adhesive system where the ethylenically unsaturated monomers remain uncured during application, allowing the adhesive to be positioned and adjusted. Upon curing (via UV exposure or other activation), the system transitions to a rigid bonded state. This dynamic transition resolves the contradiction between processing flexibility and bonding strength.
Solution Approach 2:
The adhesive composition is prepared with all necessary components (SIS block copolymer, ethylenically unsaturated monomers, initiators) in advance, but the curing reaction is postponed until after application. This preliminary preparation without immediate curing allows for flexible application and positioning, followed by strength enhancement through subsequent curing.
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 described compositions demonstrate improved adhesion, cohesive strength, and refractive index adjustment, enabling better bonding and optical clarity, suitable for applications in electronic devices and optical coatings.
Implementation Method 1
at least one ethylenically unsaturated monomer comprising one or more groups selected from (meth)acryl or vinyl ether... curing the at least one ethylenically unsaturated monomer
Data Source
AI summary
Compositions are described comprising at least 20 wt.% of block copolymer comprising polyvinyl aromatic end blocks and a polyisoprene midblock and at least one ethylenically unsaturated monomer comprising one or more groups selected from (meth)acryl or vinyl ether. In one embodiment, the monomer has a Log P according to Moriguchi's method of at least 2.2. In another embodiment, the monomer is a multifunctional aromatic ethylenically unsaturated monomer. The composition is typically a (e.g. pressure sensitive) adhesive. Also described are methods of making an article, adhesive articles, and methods of bonding.