Liquid Optical Adhesive Composition for Haze-Free Bonding
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Solution Overview
Problem
Optically clear adhesives used in optical displays, such as LCDs, face issues like bubbling and delamination under high temperature and humidity conditions due to poor compatibility with moisture, leading to haze and optical clarity loss.
Innovation Solution
A curable composition comprising a solute (meth)acryloyl oligomer with pendent ethylenically unsaturated functional groups and hydroxyl groups, a solvent monomer component, a chain transfer agent, and a photoinitiator, which forms a non-yellowing, low-shrinkage adhesive with low birefringence and high moisture-vapor transmission rate, ensuring optical clarity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional adhesives are used in optical displays, then bonding function is achieved, but bubbling and delamination occur under high temperature and humidity conditions
Solution Approach 1:
The patent modifies the chemical composition parameters of the adhesive by incorporating hydrophilic moieties and specific oligomer structures with controlled molecular weights (5k-30k) and glass transition temperatures (Tgg 50-150°C). These parameter changes enable the adhesive to maintain bond stability while resisting bubbling and delamination under high temperature and humidity conditions.
Solution Approach 2:
The adhesive composition is formulated as a composite system containing multiple functional components: (meth)acryloyl oligomers with hydroxyl groups, photoinitiators, and hydrophilic additives. This composite structure combines the bonding capabilities of acrylate polymers with the moisture compatibility of hydrophilic materials, resolving the contradiction between adhesion strength and humidity resistance.
2Strength
If adhesive is used to bond optical components, then structural integrity is achieved, but optical clarity is lost due to haze and yellowing
Solution Approach 1:
The patent carefully controls the molecular weight (5k-30k) and glass transition temperature (Tgg 50-150°C) parameters of the oligomer to achieve an optimal balance between bond strength and optical clarity. The low molecular weight ensures good flow and wetting for strong bonding, while the controlled Tgg prevents excessive crosslinking that would cause yellowing and haze.
Solution Approach 2:
The adhesive formulation specifically addresses color stability by selecting oligomer structures and additives that resist yellowing under UV exposure and thermal stress. The composition maintains high light transmission and low yellowing index, ensuring optical clarity is preserved while achieving adequate bond strength for optical components.
3Strength
If adhesive with high crosslink density is used, then bond strength is improved, but moisture compatibility deteriorates leading to clouding
Solution Approach 1:
The patent creates a composite adhesive system that combines crosslinkable acrylate oligomers with hydrophilic moieties. The hydrophilic components act as compatibility agents that prevent phase separation and clouding caused by moisture, while the acrylate groups provide crosslinking capability for strong bonding. This composite approach resolves the contradiction between crosslink density and moisture compatibility.
Solution Approach 2:
The adhesive formulation incorporates hydrophilic moieties at specific concentrations (0.1-10 wt%) to create localized regions of improved moisture compatibility within the adhesive matrix. These localized hydrophilic domains prevent water accumulation and phase separation without significantly compromising the overall crosslink density and bond strength of the adhesive system.
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 haze-free, cloud point-resistant optical clarity even after accelerated aging tests, maintaining high light transmission and bond strength across varying temperature and humidity environments.
Implementation Method 1
a curable composition comprising a) a solute (meth)acryloyl oligomer having a plurality of pendent, ethylenically unsaturated, free-radically polymerizable functional groups
Implementation Method 2
c) a chain transfer agent
Data Source
AI summary
The disclosure describes a curable composition comprising a) a solute (meth)acryloyl oligomer having a plurality of pendent, ethylenically unsaturated, free-radically polymerizable functional groups and nucleophilic, hydrophilic groups, a Mw of 5 k to 30 k, a Tg<20° C.; b) a solvent monomer component; a chain transfer agent, and a photoinitiator. The curable composition may be used as an adhesive in optical applications.