Thermally Stable Ink Layers for Flexible Packaging
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Solution Overview
Problem
Flexible packaging substrates printed with conventional inks suffer from limited thermal stability, leading to color changes and design deformations during heat sealing due to ink softening and flowing under pressure, especially in direct contact sealing applications where temperature ranges are between 120 and 200°C.
Innovation Solution
The use of digitally-printed electron beam crosslinked ink layers with carbon-carbon crosslinks, characterized by tertiary or quaternary carbon atoms, and low concentrations of ethylenically unsaturated groups and alicyclic epoxides, which are subjected to electron beam irradiation in an oxygen-poor environment, providing thermal stability without the need for additional protective layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional inks are used for printing flexible packaging substrates, then the printing process is simple and cost-effective, but the thermal stability is limited causing color changes and design deformations during heat sealing
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition of the ink, specifically incorporating polymers with glass transition temperatures above the heat sealing temperature range (120-200°C). This changes the thermal behavior parameter of the ink from softening at sealing temperatures to remaining stable, thereby resolving the contradiction between thermal stability and printing process simplicity.
Solution Approach 2:
The patent uses composite materials by combining conventional ink formulations with thermally stable polymer resins that have glass transition temperatures above the heat sealing range. This creates a composite ink system that maintains the ease of conventional printing while adding thermal stability, resolving the contradiction between reliability and device complexity.
2Reliability
If additional protective layers are applied to improve thermal stability, then thermal stability is enhanced, but the device complexity and production steps increase
Solution Approach 1:
The patent merges the protective function with the ink layer itself by incorporating thermally stable polymers directly into the ink formulation. This eliminates the need for separate protective layers while achieving the same thermal stability function, thereby resolving the contradiction between reliability and ease of manufacture.
Solution Approach 2:
The patent makes the ink layer multi-functional by giving it both the printing function and the thermal protection function through the incorporation of heat-stable polymers. This eliminates the need for additional specialized protective layers, resolving the contradiction between enhanced thermal stability and production simplicity.
3Reliability
If heat sealing is performed at high temperatures (120-200°C), then sealing effectiveness is achieved, but ink softening and flowing occur causing defects
Solution Approach 1:
The patent changes the thermal parameter of the ink by selecting polymers with glass transition temperatures above the heat sealing range. This allows the ink to withstand high sealing temperatures without softening, thereby resolving the contradiction between sealing effectiveness and print quality.
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 electron beam crosslinked ink layers exhibit enhanced thermal stability, allowing for heat sealing without defects such as ink removal or gloss changes, even at high temperatures, and maintain high optical quality without the need for additional protective coatings.
Implementation Method 1
wherein the one or more crosslinked ink layers are obtained from a digital print, subjected to an electron beam irradiation
Implementation Method 2
the crosslinks comprise carbon-carbon bonds, wherein each of the carbons independently is a tertiary or quaternary carbon
Data Source
AI summary
The present invention is related to a flexible packaging substrate comprising one or more crosslinked ink layers and to a method for the production of said printed substrate.