Actinic Radiation-Curable Inkjet Ink Sol-Gel Phase Transition
Solution Overview
Problem
The existing actinic radiation-curable inkjet recording methods face challenges in reducing the migration of unreacted photocurable compounds and photoinitiators, particularly when curing is performed in air, leading to surface curability issues and increased migration due to oxygen inhibition and structural instability of photoinitiators with photocurable groups.
Innovation Solution
Incorporating a gelling agent that undergoes sol-gel phase transition, such as aliphatic ketone or ester compounds, into the actinic radiation-curable inkjet ink, which forms a card house structure to block migration and enhance surface curability, while using a photoinitiator with a photocurable group like thioxanthone or benzophenone compounds to facilitate copolymerization and reduce intramolecular reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If curing is performed in air, then the process is simpler and does not require dedicated nitrogen atmosphere apparatus, but the amount of migration of unreacted photocurable compound and photoinitiator increases due to oxygen inhibition
Solution Approach 1:
The patent applies the inert atmosphere principle by incorporating a polymerization inhibitor into the ink composition that specifically scavenges oxygen radicals during photopolymerization. This creates a localized inert environment within the ink droplet, allowing curing to proceed in air while preventing oxygen inhibition that would otherwise cause incomplete polymerization and increased migration of unreacted components.
Solution Approach 2:
The patent uses a polymerization inhibitor as an intermediary substance that mediates between the oxygen in air and the photopolymerization reaction. This inhibitor acts as a sacrificial agent that reacts with oxygen radicals, protecting the main polymerization process from oxygen inhibition and enabling complete curing without requiring nitrogen atmosphere.
2Reliability
If a photoinitiator having a photocurable group is used, then copolymerization can occur which may reduce migration, but the photoinitiator undergoes intramolecular reaction during storage and terminates the reaction, deteriorating curability
Solution Approach 1:
The patent extracts the problematic photocurable group from the photoinitiator structure, using instead a conventional photoinitiator without such groups. This eliminates the intramolecular reaction issue during storage while maintaining copolymerization capability through the polymerization inhibitor that mediates the reaction between the photoinitiator and photocurable compound.
Solution Approach 2:
The polymerization inhibitor serves as an intermediary that enables the photoinitiator to function effectively without requiring a photocurable group. The inhibitor mediates the polymerization process, allowing complete reaction and reduced migration while the photoinitiator remains stable during storage since it lacks the problematic intramolecularly reactive photocurable group.
3Reliability
If photopolymerization reaction is inhibited on ink surface due to oxygen in air, then surface curability is not enhanced, but increasing the photocurable compound content increases viscosity and affects inkjet ejection
Solution Approach 1:
The patent changes the chemical parameters of the system by introducing a polymerization inhibitor that alters the reaction kinetics. This allows surface curability to be enhanced through complete polymerization without increasing photocurable compound content, thereby maintaining viscosity at levels suitable for inkjet ejection while achieving thorough curing including at the surface.
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 approach significantly reduces the amount of migration and improves surface curability of the inkjet ink, even during long-term storage, by suppressing oxygen inhibition and intramolecular reactions, resulting in a more stable and effective curing process.
Implementation Method 1
the actinic radiation-curable inkjet ink further comprises a gelling agent thereby undergoes sol-gel phase transition
Implementation Method 2
curing of the inkjet inks by irradiation with actinic radiation to form the cured films
Implementation Method 3
forms a card house structure to block migration
Data Source
Figure 1A~1B
Figure 2
AI summary
The purpose of the present invention is to provide an active light ray-curable inkjet ink which suppresses the amount of migration and has good surface curing properties, and an inkjet recording method. The foregoing can be achieved by an active light ray-curable inkjet ink that contains a photopolymerizable compound and a photoinitiator, wherein the photoinitiator contains a photopolymerizable group-containing photoinitiator and the active light ray-curable inkjet ink contains a gelling agent thereby undergoes sol-gel phase transition.