Low-Viscosity Inkjet Varnish for High-Speed Curing
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Solution Overview
Problem
The reduction in viscosity of varnishes for new inkjet printing technologies leads to longer drying or polymerization times, reducing printing rates and requiring heating, which can damage printheads and increase energy consumption.
Innovation Solution
A varnish composition with a specific ratio of hardenable oligomers and monomers, including alkoxylated acrylic monomers and a bis-(2,4,6-trimethylbenzoyl)-phenylphosphine oxide photoinitiator, with a viscosity between 5 mPa.s and 40 mPa.s, that can be rapidly dried and polymerized at low temperatures without heating the substrate, using a process involving mixing, cooling, and filtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the viscosity of the varnish is reduced to adapt to new inkjet printing technologies, then the varnish can be deposited by new print heads, but the drying or polymerization time increases and printing rates are reduced
Solution Approach 1:
The patent changes the chemical composition parameters of the varnish by using a specific ratio of oligomers to monomers (1/6 to 1/25 by weight) and selecting particular photoinitiators, which fundamentally alters the polymerization kinetics to enable fast curing despite low viscosity
Solution Approach 2:
The patent creates a composite varnish system combining oligomers, monomers, and photoinitiators in specific proportions, where the synergistic interaction between components enables both low viscosity for inkjet deposition and rapid polymerization for high productivity
2Adaptability or versatility
If the viscosity of the varnish is reduced to adapt to new inkjet printing technologies, then the varnish can be deposited by new print heads, but heating is required which increases energy consumption and can damage printheads
Solution Approach 1:
The patent replaces the thermal field (heating) with a photonic field (UV or visible light irradiation) to initiate polymerization, eliminating the need for thermal energy input and associated energy consumption and heating risks
Solution Approach 2:
The patent selects photoinitiators with absorption spectra matching UV or visible light sources, changing the activation mechanism from thermal to photonic, which enables energy-efficient curing without heating the substrate or printhead
3Adaptability or versatility
If the viscosity of the varnish is reduced to adapt to new inkjet printing technologies, then the varnish can be deposited by new print heads, but the polymerization time increases which reduces printing rates
Solution Approach 1:
The patent fundamentally changes the polymerization kinetics by selecting photoinitiators with high quantum efficiency and matching absorption spectra, and by using monomers with high reactivity, enabling rapid polymerization within seconds of UV or visible light exposure
Solution Approach 2:
The patent employs intense, short-duration UV or visible light irradiation pulses that deliver sufficient photon flux to initiate and complete polymerization rapidly, reducing the effective polymerization time despite low varnish viscosity
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 varnish allows for high printing rates with low viscosity varnishes, avoiding heating and extending printhead life, while maintaining efficient polymerization and energy efficiency.
Implementation Method 1
a photo-initiator, in that at least one photoinitiator is a bis-(2,4,6-trimethylbenzoyl)-phenylphosphine oxide
Data Source
Figure 1
AI summary
The present invention relates to a varnish which is for covering the surface of a printed substrate and deposited by inkjet, in which the composition of the varnish comprises at least: - at least one curable oligomer, - at least one curable monomer and - at least one photoinitiator.