Acrylic Adhesive Composition for Touch Panel ITO Pattern Hiding
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Solution Overview
Problem
Adhesives used in touch panels fail to maintain adhesion under high-temperature and high-humidity conditions, causing separation from the conductive layer and revealing the ITO pattern due to heat-induced separation and subsequent water condensation.
Innovation Solution
An adhesive composition comprising a partially polymerized acrylic resin with a weight average molecular weight of 1,000,000 or higher, a multifunctional crosslinking agent, and urethane acrylate, which provides a shear strength of 20 kg/in² or higher at 100°C, ensuring durability and maintaining adhesion to the conductive layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional adhesive is used to attach transparent conductive film to conductive layer, then initial adhesion and surface leveling are achieved, but adhesion deteriorates under high-temperature and high-humidity conditions causing separation and ITO pattern visibility
Solution Approach 1:
The patent changes the chemical composition parameters of the adhesive by incorporating silane crosslinking agents and specific monomer ratios (alkyl (meth)acrylate 70-99.9 parts, crosslinkable functional group monomer 0.1-30 parts) to create a adhesive that maintains its bonding properties at elevated temperatures up to 100°C, preventing separation under high-temperature and high-humidity conditions
Solution Approach 2:
The patent creates a composite adhesive system combining multiple components: silane crosslinking agent, alkyl (meth)acrylate monomer, and crosslinkable functional group monomer. This composite formulation provides both initial adhesion and long-term durability under severe environmental conditions through synergistic effects of the different materials
2Manufacturing precision
If adhesive completely fills etched uneven surface of ITO immediately after attachment, then ITO pattern is hidden, but adhesive separates from ITO under high-temperature conditions creating space for vapor condensation
Solution Approach 1:
The patent performs preliminary filling of the etched uneven surface of ITO with the adhesive composition, which then cures to form a stable bonded layer. This preliminary action ensures the ITO pattern is hidden while the crosslinked adhesive structure maintains stable bonding under high-temperature conditions, preventing subsequent separation that would create vapor condensation spaces
3Strength
If adhesive is used to attach transparent conductive film, then surface leveling and initial bonding are achieved, but adhesive sticks out or is squeezed when cut
Solution Approach 1:
The patent adjusts the viscosity and curing characteristics parameters of the adhesive by controlling the monomer composition and silane crosslinking agent amount, enabling the adhesive to maintain strong bonding while allowing clean cutting without sticking out or squeezing during assembly operations
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 effectively hides the ITO pattern even under high-temperature and high-humidity conditions by maintaining strong adhesion and preventing yellowing or whitening, ensuring reliable performance in touch panels.
Implementation Method 1
a partially polymerized acrylic resin; a multifunctional crosslinking agent; and urethane acrylate
Implementation Method 2
a multifunctional crosslinking agent, and urethane acrylate... the multifunctional crosslinking agent comprises multifunctional (meth)acrylates
Implementation Method 3
a cured product of the adhesive composition... measured at 100°C that is a cured product of the adhesive composition
Data Source
Figure 1~3
Figure 4
AI summary
The present invention relates to an adhesive composition for a touch panel, an adhesive film, and a touch panel. The adhesive composition for the touch panel of the present invention is applied to the touch panel, for example, to an electrostatic capacitance-type touch panel, for hiding the pattern of a conductive layer even when being coupled to the conductive layer formed with the pattern. Also, the adhesive composition of the present invention can prevent yellowing and whitening.