Biphenyl-Modified Pressure-Sensitive Adhesives for Optical Clarity
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Solution Overview
Problem
Typical pressure-sensitive and heat-activated adhesives have refractive indices of about 1.47 or less, which can lead to glare and reflectance issues in optical applications where substrates have higher refractive indices, necessitating adhesives with higher refractive indices to match the substrate and enhance optical properties.
Innovation Solution
Development of pressure-sensitive and heat-activated adhesives with a refractive index of at least 1.50, comprising monomers with substituted or unsubstituted biphenyl groups, (meth)acrylic acid esters, acid functional monomers, and optional polar monomers, which are interpolymerized to achieve high refractive indices while maintaining adhesion, cohesion, stretchiness, and elasticity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If typical PSAs with refractive index of about 1.47 or less are used, then adhesive properties are maintained, but glare and reflectance occur in optical applications
Solution Approach 1:
The patent changes the refractive index parameter of the PSA from typical values of 1.47 or less to at least 1.50 by incorporating specific monomers (biphenyl group-containing monomers, styrene, and their copolymers) into the adhesive formulation. This parameter change allows the adhesive to match the refractive index of optical substrates, thereby reducing glare and reflectance while maintaining adhesive performance.
Solution Approach 2:
The patent creates a composite adhesive system by combining multiple components: (a) a polymer component, (b) a biphenyl group-containing monomer component, (c) a styrene component, and (d) optionally a copolymer component. This composite formulation achieves the target refractive index of at least 1.50 while maintaining the necessary adhesive properties through the synergistic combination of these materials.
2Quantity of substance
If monomers with biphenyl groups are incorporated to increase refractive index, then optical properties improve, but adhesive properties may be compromised
Solution Approach 1:
The patent carefully controls the composition parameters to achieve the desired refractive index while maintaining adhesive reliability. Specifically, it requires the biphenyl group-containing monomer to be present at 5-95 parts by weight per 100 parts by weight of total monomers, with styrene at 5-95 parts by weight per 100 parts by weight of total monomers. These controlled compositions ensure the adhesive maintains its balance of adhesion, cohesion, stretchiness, and elasticity while achieving the target optical properties.
Data Source
AI summary
The present invention provides pressure-sensitive adhesives having a refractive index of at least 1.50. The pressure-sensitive adhesives comprise at least one monomer containing a substituted or an unsubstituted biphenyl group.