Shear-Thinning Optical Adhesive for Overflow Control
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Solution Overview
Problem
Current photo-curable optically clear adhesives face challenges such as adhesive overflow, suboptimal application processes, and reduced optical performance due to air gaps or bubbles, particularly in touch displays and other optical bonding applications.
Innovation Solution
A photo-curable liquid optically clear adhesive composition comprising a (meth)acrylic copolymer, non-functional (meth)acrylic monomers, a photo initiator, and functional (meth)acrylic monomers, which can be applied using a slit coater and cured with high efficiency to prevent overflow and maintain optical clarity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a dispensable fluid LOCAs is used for bonding, then the adhesive can be easily applied, but it flows beyond the desired printing area causing overflow
Solution Approach 1:
The patent modifies the rheological parameters of the LOCAs by adding shear-thinning agents, causing the adhesive to exhibit non-Newtonian fluid behavior. The viscosity decreases under shear stress during application (enabling easy coating) and increases at rest (preventing overflow), thus resolving the contradiction between ease of application and edge control.
2Manufacturing precision
If a pre-cured dam material is used to prevent overflow, then adhesive overflow is controlled, but the process becomes complicated and requires two steps
Solution Approach 1:
The patent removes the dam material component from the bonding process entirely. By modifying the LOCAs formulation to exhibit shear-thinning behavior, the adhesive inherently controls its own flow without requiring external containment structures, thus eliminating the complex two-step damming process.
Solution Approach 2:
The LOCAs formulation self-regulates its flow behavior through shear-thinning properties. During application, the adhesive flows easily under shear stress, then automatically increases viscosity at rest to prevent overflow, making the system self-containing without external dams or complex processes.
3Manufacturing precision
If optically clear tapes are used to prevent overflow, then adhesive overflow is controlled, but air gaps or bubbles form reducing optical performance
Solution Approach 1:
The patent replaces the mechanical containment system (optically clear tapes forming physical barriers) with a rheological control system (shear-thinning LOCAs that self-regulate flow). This substitution eliminates air gaps and bubbles associated with tape application while maintaining overflow control through viscosity modulation.
4Ease of operation
If the adhesive has high flowability for easy application, then it can be well applied by slit coaters, but it overflows beyond the bonding area
Solution Approach 1:
The patent introduces dynamic viscosity control to the LOCAs formulation. The adhesive viscosity is not fixed but dynamically adjusts based on shear rate: low viscosity during application (enabling slit coater processing) and high viscosity at rest (ensuring boundary control), thus resolving the static contradiction between flowability and containment.
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 achieves excellent hardness, haze, transmittance, and tackiness, allowing for efficient edge control and bonding without the need for a dam, while maintaining high optical performance and avoiding air gaps or bubbles.
Implementation Method 1
curing the photo-curable liquid optically clear adhesive composition by exposure to electromagnetic radiation having a wavelength ranging from 200 nm to 500 nm
Data Source
AI summary
The present invention relates to a photo-curable liquid optically clear adhesive composition, to a cured adhesive and an article produced therefrom, and to the use thereof.