Actinic Inkjet Ink Migration Control via Sol-Gel Phase Transition
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Solution Overview
Problem
The actinic radiation-curable inkjet recording method faces challenges in reducing the migration of unreacted photocurable compounds, photoinitiators, and residues in cured films, particularly in food packaging applications, where strict regulations like the Swiss Ordinance require less than 10 ppb migration.
Innovation Solution
An actinic radiation-curable inkjet ink formulation is developed, comprising a polyfunctional photocurable compound, an α-hydroxy ketone compound with a specific molecular weight, and a gelling agent that undergoes sol-gel phase transition, forming a card house structure to act as a filter and enhance viscosity, thereby reducing migration and improving surface curability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional actinic radiation-curable inkjet ink is used, then the ink can be applied on non-absorptive recording media and cured, but unreacted photocurable compounds, photoinitiators, and residues migrate from the cured film
Solution Approach 1:
The patent changes the molecular weight parameter of the photoinitiator to 210-3000 range and uses specific polyfunctional photocurable compounds with controlled functionality (2-6 functional groups). These parameter changes optimize the balance between adhesion performance and migration reduction, achieving compliance with Swiss Ordinance requirements while maintaining reliable adhesion on non-absorptive media.
Solution Approach 2:
The patent creates a composite ink formulation combining multiple components: polyfunctional photocurable compounds (2-6 functional groups), α-hydroxy ketone photoinitiators with specific molecular weights, and other photoinitiators (acylphosphine, α-amino ketone, benzophenone, or thioxanthone compounds). This composite approach synergistically reduces migration of unreacted compounds while maintaining adhesion performance.
2Object-generated harmful factors
If polyfunctional photocurable compounds are used to reduce migration, then crosslinking structure forms to reduce unreacted compound migration, but the formulation complexity increases
Solution Approach 1:
The patent specifies precise parameters for the photocurable compounds: functionality of 2-6 functional groups and molecular weight control. These parameter specifications provide clear formulation guidelines that reduce complexity by eliminating trial-and-error, while achieving effective crosslinking structures that minimize unreacted compound migration.
Solution Approach 2:
The patent applies different functional groups (2-6 of them) at specific locations within the photocurable compound molecules, creating localized crosslinking density variations. This local quality approach optimizes the crosslinking structure to effectively trap unreacted compounds while maintaining overall formulation manageability.
3Object-generated harmful factors
If high molecular weight photoinitiators are used to reduce migration, then migration is reduced, but the inkjet discharge stability deteriorates
Solution Approach 1:
The patent optimizes the molecular weight parameter of the α-hydroxy ketone photoinitiator to the specific range of 210-3000. This parameter optimization achieves the dual benefit of sufficient migration reduction while maintaining inkjet discharge stability, resolving the contradiction between these two requirements.
Solution Approach 2:
The patent uses a composite photoinitiator system combining α-hydroxy ketone compounds (with controlled molecular weight for discharge stability) with other photoinitiators (acylphosphine, α-amino ketone, benzophenone, or thioxanthone compounds). This composite approach allows the α-hydroxy ketone to maintain discharge stability while the overall system achieves migration reduction.
4Object-generated harmful factors
If strict regulatory compliance is achieved for food packaging, then migration is reduced to below 10 ppb, but the formulation requirements become more stringent
Solution Approach 1:
The patent establishes specific parameter ranges that guarantee Swiss Ordinance compliance: photoinitiator molecular weight of 210-3000, photocurable compound functionality of 2-6, and controlled ratios of different photoinitiators. These parameter specifications provide a clear formulation framework that achieves migration reduction to below 10 ppb while simplifying the manufacturing process through standardized requirements.
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 inkjet ink effectively minimizes the migration of unreacted compounds and residues, meeting strict regulatory standards such as the Swiss Ordinance, while maintaining discharge stability and surface curability.
Implementation Method 1
the actinic radiation-curable inkjet ink contains a gelling agent and undergoes sol-gel phase transition
Implementation Method 2
an actinic radiation cure-type inkjet recording method, which performs recording by impacting droplets of an inkjet ink on a recording medium, and then irradiating the inkjet ink with actinic radiation to cure
Implementation Method 3
it is believed that a card house structure (filter) is formed due to crystals produced by the gelling agent upon impact of an actinic radiation-curable inkjet ink on a recording medium
Data Source
Figure 1A~1B
Figure 2
AI summary
The purpose of the present invention is to provide an actinic radiation-curable inkjet ink and inkjet printing method with which the amount of migration is limited and can satisfy even strict regulations such as the Swiss Ordinance. This actinic radiation-curable inkjet ink is an actinic radiation-curable inkjet ink containing a photopolymerizable compound and a photoinitiator, wherein: the photopolymerizable compound is obtained substantially from a multifunctional photopolymerizable compound; the photoinitiator contains an α-hydroxy ketone compound; the molecular weight of said α-hydroxy ketone compound is 210 to 3000; and the actinic radiation-curable inkjet ink contains a gelling agent and undergoes sol-gel phase transitions.