Water-Based UV Inkjet Ink Curing with Tertiary Amine

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Solution Overview

Problem

Current water-based UV curable inkjet inks face challenges with high film thickness leading to substrate distortion and limited substrate choices due to thermal load, and there is a lack of suitable photoinitiators for UV LED curing in water-based systems.

Innovation Solution

The development of a water-based inkjet ink composition that includes a tertiary amine and an acid functional photoinitiator, such as 2-carboxymethoxy thioxanthone, allowing for rapid low-dosage UV curing using UV LED light sources, with a high ratio of amine synergists to photoinitiator for effective curing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If water-based UV curable ink is used to deposit film thickness of 10-12 microns, then resistance properties are improved, but substrate distortion and roll distortion increase

Engineering Contradiction:

Improveresistance propertiesVSAvoidsubstrate distortion

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The ink is applied with water that will be removed before UV curing, allowing the initial film thickness to be high (10-12 microns) for good resistance properties, but the water removal step reduces the film thickness to a few microns before curing, thereby preventing substrate distortion during the curing process

Inventive Principle:

Principle #10Preliminary action

2Manufacturing precision

If water is removed from printed ink before UV curing, then substrate distortion is reduced, but thermal load on substrate increases

Engineering Contradiction:

Improvesubstrate distortionVSAvoidthermal load

Core Design Contradiction:

Manufacturing precisionVSTemperature

Solution Approach 1:

The process combines water removal and UV curing in a continuous operation where the UV LED lamp performs both functions simultaneously - removing water through low-level heating and curing the ink through UV radiation, eliminating the need for separate high-heat drying step

Inventive Principle:

Principle #20Continuity of useful action

Solution Approach 2:

The patent replaces conventional medium pressure mercury arc lamps with UV LED lamps that emit at 395nm, substituting a high-thermal-load curing system with a low-thermal-load system that uses photopolymerization initiated by specific wavelength light absorption

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Adaptability or versatility

If UV LED lamp is used to reduce thermal load, then substrate choices are expanded, but suitable photoinitiators are limited

Engineering Contradiction:

Improvesubstrate choicesVSAvoidphotoinitiator selection

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent changes the photoinitiator selection criterion from conventional UV wavelengths (300-365nm) to match the UV LED emission wavelength of 395nm, selecting thioxanthone derivatives which have absorption maxima at 395nm, thereby enabling effective curing with UV LED lamps

Inventive Principle:

Principle #35Parameter changes

4Productivity

If thioxanthone photoinitiator is used for UV LED curing, then curing efficiency is improved, but water solubility decreases

Engineering Contradiction:

Improvecuring efficiencyVSAvoidwater solubility

Core Design Contradiction:

ProductivityVSStability of the object's composition

Solution Approach 1:

The patent uses a co-solvent system where a water-miscible organic solvent (such as ethylene glycol monomethyl ether acetate or propylene glycol monomethyl ether acetate) acts as an intermediary to dissolve the thioxanthone photoinitiator and other hydrophobic components, enabling their incorporation into the water-based ink formulation

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The ink formulation is a composite system combining water, co-solvents, polymers, photoinitiators, and pigments, where each component contributes specific properties and the synergistic interaction enables both water solubility and effective UV LED curing

Inventive Principle:

Principle #40Composite materials

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

This solution enables efficient curing of water-based UV formulations with UV LED light, reducing substrate distortion and expanding substrate choices while maintaining resistance properties, with improved performance at higher amine levels than conventional ratios.

Implementation Method 1

a photoinitiator of Formula I... allowing the rapid low dosage UV curing of the water-based UV formulation using a UV LED light source

Methodology Applied

Scientific EffectPhotopolymerisation: Photopolymerisation

Implementation Method 2

UV LED light source... UV LED lamps emit light

Methodology Applied

Scientific EffectLight Emitting Diode: Light Emitting Diode

Data Source

PatentEP3148980B1Water-based UV inkjet ink

Publication Date: 2020.12.09 SUN CHEMICAL CORP

Figure 1

AI summary

The invention describes the use of a water-based UV curable inkjet printing ink wherein the ink is basic due to the presence of a tertiary amine, allowing the complete dissolution of an acid functional photoinitiator of Formula I or Formula IA (wherein R1, R2, R3, n, q, and y are as defined herein). This combination of photoinitiator and tertiary amine allows the rapid low dosage UV curing of a water-based UV formulation using a UV LED light source.