LED Crosslinked Pressure-Sensitive Adhesive Coating
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Solution Overview
Problem
Hot-melt coating of pressure-sensitive adhesives requires sequential coating and crosslinking due to competing requirements for smooth application and high shear performance, which can lead to undesirable crosslink density gradients and reduced tack.
Innovation Solution
Exposing a radiation crosslinkable pressure-sensitive adhesive composition to radiation from a light-emitting diode (LED) for crosslinking, which improves high temperature shear performance while maintaining tack and adhesion, and reduces local heating and surface crosslinking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If hot-melt coating is performed prior to crosslinking, then smooth coating is achieved, but crosslink density gradients and reduced tack occur
Solution Approach 1:
The patent combines coating and crosslinking operations into a single sequential process where the adhesive is coated and then immediately crosslinked in-situ. This merging eliminates the time gap between coating and crosslinking that causes crosslink density gradients, while the controlled crosslinking parameters ensure uniform crosslinking throughout the adhesive layer.
Solution Approach 2:
The patent applies preliminary crosslinking action during the coating process itself by incorporating photoinitiators and crosslinking agents into the adhesive composition before coating. The adhesive is then crosslinked immediately upon coating using UV or other radiation sources, preventing the development of crosslink density gradients that would occur with delayed crosslinking.
2Strength
If high crosslinking is achieved, then high shear performance is improved, but tack is reduced
Solution Approach 1:
The patent applies local quality by using different types of crosslinking agents with different reactivities and by controlling the spatial distribution of photoinitiators within the adhesive layer. This allows regions with different crosslink densities to coexist, providing high shear strength in the bulk while maintaining adequate tack at the adhesive-substrate interface.
Solution Approach 2:
The patent changes crosslinking parameters including radiation wavelength, intensity, and exposure time to control the degree and rate of crosslinking. By adjusting these parameters, the patent achieves optimal balance between shear performance and tack, preventing excessive crosslinking that would harm adhesive properties.
3Productivity
If traditional UV sources are used for crosslinking, then crosslinking efficiency is achieved, but energy consumption and heat emission increase
Solution Approach 1:
The patent replaces traditional high-power UV lamp systems with LED-based radiation sources. LEDs consume significantly less electrical energy to produce the required UV or visible radiation for crosslinking, while emitting far less heat. This substitution maintains crosslinking efficiency while dramatically reducing energy consumption and heat generation.
Solution Approach 2:
The patent changes the spectral parameters of the radiation source by using LEDs that emit at specific wavelengths optimized for the photoinitiators in the adhesive. This targeted wavelength approach improves crosslinking efficiency per unit energy input compared to broad-spectrum UV lamps, further reducing overall energy consumption.
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 enhances the high temperature shear performance of pressure-sensitive adhesives by achieving consistent crosslinking without compromising tack, and reduces energy consumption and heat emission compared to traditional UV sources.
Implementation Method 1
exposing at least one radiation crosslinkable pressure-sensitive adhesive composition to radiation from at least one light-emitting diode to crosslink the radiation crosslinkable pressure-sensitive adhesive composition
Implementation Method 2
exposing at least one radiation crosslinkable pressure-sensitive adhesive composition to radiation from at least one light-emitting diode to crosslink the radiation crosslinkable pressure-sensitive adhesive composition
Data Source
AI summary
A method of preparing a crosslinked pressure-sensitive adhesive is provided, including exposing at least one radiation crosslinkable pressure-sensitive adhesive composition to radiation from at least one light-emitting diode to crosslink the radiation crosslinkable pressure-sensitive adhesive composition. The crosslinked pressure-sensitive adhesive is optionally a hot melt processable pressure-sensitive adhesive. A radiation crosslinked pressure-sensitive adhesive is provided, prepared by the method. Also, an adhesive article is provided including a flexible backing layer and the radiation crosslinked pressure-sensitive adhesive prepared by the method. The crosslinked pressure-sensitive adhesive tends to exhibit high shear without sacrificing peel force or tack.