UV Curable Inkjet Compositions with Cationic Photoinitiators
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Solution Overview
Problem
Current UV-curable inkjet systems face limitations in achieving high gloss and fast cure speeds due to high viscosity and solubility issues with photoinitiators, and previous hybrid formulations of vinyl ether and acrylate functionalities have not been effectively cured using a cationic mechanism, especially with the latest inkjet printhead technology requiring lower viscosities.
Innovation Solution
A UV-curable ink or coating composition comprising a blend of vinyl ether and acrylate monomers/oligomers with a cationic photoinitiator, such as iodonium salts, and a thioxanthone or anthracene sensitizer, which allows for low viscosity and fast curing at line speeds exceeding 75 m/min, achieving high gloss levels and suitable for inkjet printers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cationic curable formulations use cycloaliphatic epoxides and vinyl ether compounds, then cationic curing is achieved, but formulation viscosity becomes too high for latest inkjet printhead technology
Solution Approach 1:
The patent changes the chemical composition parameters by replacing traditional cycloaliphatic epoxides with acrylate monomers and oligomers in the formulation. This parameter change maintains cationic curing effectiveness through the use of cationic photoinitiators while dramatically reducing formulation viscosity to levels suitable for latest inkjet printhead technology (viscosities below 10 cP at 25°C).
Solution Approach 2:
The patent creates a composite curable formulation that combines acrylate monomers, acrylate oligomers, and cationic photoinitiators. This composite material approach integrates multiple functional components: acrylates provide low viscosity and polymerizable functionality, while cationic photoinitiators enable effective curing. The composite formulation achieves both low viscosity and reliable curing that neither component could achieve alone.
2Weight of moving object
If acrylate compounds are used in high levels in cationic photoinitiator systems, then viscosity is reduced, but cure speed and mechanical properties deteriorate
Solution Approach 1:
The patent introduces cationic photoinitiators as intermediary agents that mediate between the acrylate compounds and the curing process. These photoinitiators generate cationic species that initiate and propagate polymerization of acrylate groups, enabling cure speeds and mechanical properties comparable to traditional vinyl ether systems while maintaining the low viscosity benefits of high acrylate content formulations.
3Productivity
If photoinitiator concentration is increased to achieve fast curing, then cure speed improves, but solubility issues and formulation stability worsen
Solution Approach 1:
The patent optimizes the concentration parameter of cationic photoinitiators to achieve an optimal balance point. By carefully controlling photoinitiator levels and selecting specific cationic photoinitiator compounds with appropriate solubility characteristics, the formulation achieves fast curing speeds while maintaining excellent formulation stability and avoiding solubility issues that plague traditional formulations.
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 composition enables exceptionally fast curing and good mechanical properties at very low viscosities, suitable for the latest inkjet printheads, with high gloss levels and resistance properties, even at low UV cure doses, making it suitable for various printing and coating applications, including printed electronics.
Implementation Method 1
UV curable compositions comprising a vinyl ether containing monomer (and/or oligomer), an acrylate monomer (and/or oligomer) and a cationic photoinitiator
Data Source
AI summary
UV curable compositions comprising vinyl ether and acrylate compounds and a cationic photo initiator system. The compositions of the invention are particularly useful for the preparation of highly reactive and very low viscosity systems that may be applied via any printing or coating method, although inkjet printing is the preferred method. The inventive compositions can be cured with doses of 100 mJ/cm2 or less and deliver highly resistant surfaces.