Photoactivatable Redox Adhesive Printing for Opaque Substrates
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Solution Overview
Problem
Redox-curing adhesive precursor compositions cure rapidly, limiting their utility in stencil/screen printing applications due to reduced latent time, and photoactivatable adhesives are restricted to transparent materials due to rapid curing upon light exposure.
Innovation Solution
A photoactivatable adhesive precursor composition is used, comprising a photoactivatable reducing agent activated by actinic electromagnetic radiation, allowing for controlled curing and extended latent time, suitable for both transparent and opaque substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If redox-curing adhesive precursor compositions are used, then bonding capability for non-transparent materials is improved, but latent time is reduced leading to rapid cure
Solution Approach 1:
The adhesive precursor composition is prepared in advance with all components (polymerizable compound, transition metal compound, and photoactivatable reducing agent) but remains stable and uncured until the moment of application. The photoactivatable reducing agent is kept in its protected form before exposure to actinic radiation, allowing the adhesive to be stored and handled without premature curing while maintaining the capability to bond non-transparent materials.
Solution Approach 2:
The invention changes the activation parameter from direct redox reaction (which occurs rapidly upon mixing) to photoactivation (which occurs only upon exposure to actinic radiation). This parameter change allows control over when the curing reaction starts, extending the latent time while maintaining the redox-curing mechanism's ability to bond non-transparent materials.
2Loss of time
If photoactivatable adhesive precursor compositions are used, then latent time is extended, but bonding is restricted to transparent materials only
Solution Approach 1:
The invention merges two previously separate adhesive systems: the photoactivatable adhesive system (which provides extended latent time) and the redox-curing adhesive system (which provides bonding capability for non-transparent materials). By combining the polymerizable compound, transition metal compound, and photoactivatable reducing agent in one composition, the adhesive gains both the extended latent time of photoactivation and the versatility to bond transparent and non-transparent materials through redox curing.
Solution Approach 2:
The adhesive precursor composition is a composite system containing multiple functional components: a polymerizable compound for forming the adhesive matrix, a transition metal compound for redox curing, and a photoactivatable reducing agent for controlled initiation. This composite structure enables the adhesive to exhibit both photoactivatable latency and redox-curing versatility for bonding various substrate types including non-transparent materials.
3Adaptability or versatility
If traditional photoinitiators are used, then transparent materials can be bonded, but curing occurs rapidly without open time
Solution Approach 1:
The photoactivatable reducing agent serves as an intermediary between light exposure and the redox curing reaction. Upon exposure to actinic radiation, the photoremovable group is removed to generate the active reducing agent, which then initiates the redox curing process with the transition metal compound. This intermediary mechanism provides a controlled delay, creating open time for handling and positioning while still enabling curing of transparent materials through the photoactivation step.
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 method enables precise adhesive deposition on substrates with controlled curing, providing good shelf stability and allowing handling in ambient light without premature curing, suitable for both transparent and opaque materials.
Implementation Method 1
During activation a photoremovable group is removed from the photoactivatable reducing agent thereby generating the reducing agent which initiates the curing process
Implementation Method 2
at least one free-radically polymerizable compound; exposing the photoactivatable adhesive precursor composition to actinic electromagnetic radiation, thereby providing an adhesive precursor composition that spontaneously cures
Implementation Method 3
a photoactivatable redox initiation system comprising: (i) at least one photoactivatable reducing agent precursor; (ii) at least one transition metal compound comprising at least one metal selected from groups 5 to 11
Data Source
AI summary
A method of disposing an adhesive composition onto a first surface of a first substrate comprises: a) disposing a photoactivatable adhesive precursor composition onto at least a portion of the first surface of the first substrate according to a predetermined pattern, and b) exposing the photoactivatable adhesive precursor composition to actinic electromagnetic radiation, thereby providing an adhesive precursor composition that spontaneously cures to provide the adhesive composition. The photoactivatable adhesive precursor composition comprises: at least one free-radically polymerizable compound and a photoactivatable redox initiation system comprising: (i) at least one photoactivatable reducing agent precursor; (ii) at least one transition metal compound comprising at least one metal selected from groups 5 to 11 in the Periodic Table of the Elements; (iii) optional organic peroxide; and (iv) optional quaternary ammonium halide. An article preparable according to the method is also disclosed.