Radiation Curable Inkjet Ink Without Photoinitiator

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Solution Overview

Problem

Thermal inkjet printing faces issues with nozzle plate wetting, poor decap behavior, and nozzle clogging, leading to unreliable jetting and image quality degradation, while current inks with aqueous solvents or humectants suffer from long dry times and contamination concerns due to low molecular weight monomers and photoinitiator migration.

Innovation Solution

Development of radiation curable inkjet ink compositions comprising a mono-ethylenically unsaturated oligomer, a mono-ethylenically unsaturated monomer, and a solvent, without a photoinitiator, where the oligomer weight is less than or equal to the monomer weight, and the solvent weight ranges from 30 to 65%, providing a stable and non-migratory cured ink.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If aqueous solvents or humectants are used to reduce nozzle drying, then nozzle clogging is reduced, but ink dry time increases and adhesion to substrates deteriorates

Engineering Contradiction:

Improvenozzle jetting reliabilityVSAvoidink dry time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent changes the chemical composition parameters of the ink by using radiation-curable monomers and oligomers with specific functional groups instead of traditional aqueous solvents. This parameter change allows the ink to maintain proper flow characteristics during jetting while enabling rapid curing and adhesion through radiation exposure, thus resolving the contradiction between preventing nozzle clogging and reducing dry time.

Inventive Principle:

Principle #35Parameter changes

2Ease of operation

If low molecular weight monomers and additives are used to lower ink viscosity for proper jetting, then jetting performance improves, but contamination of packaged products increases due to migration

Engineering Contradiction:

Improvejetting performanceVSAvoidproduct contamination

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The patent employs composite material composition by combining radiation-curable monomers, oligomers, and photoinitiators in specific ratios. This composite formulation achieves the dual benefit of maintaining low enough viscosity for proper jetting performance while ensuring complete curing to prevent migration and contamination of packaged products, thus resolving the contradiction between jetting ease and product safety.

Inventive Principle:

Principle #40Composite materials

3Device complexity

If thermal inkjet printing uses traditional inks, then printing process is simple, but nozzle plate wetting and kogation occur leading to poor reliability

Engineering Contradiction:

Improveprinting process complexityVSAvoidprinthead reliability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent replaces the traditional thermal evaporation mechanism with a radiation-curing mechanism. Instead of relying on thermal vaporization that causes nozzle plate wetting and kogation, the ink is formulated to cure through radiation exposure, substituting the curing mechanism while maintaining the thermal jetting delivery system. This resolves the contradiction between process simplicity and printhead reliability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 solution minimizes nozzle plate wetting, improves decap behavior, and reduces migration, resulting in reliable jetting, enhanced image quality, and extended printhead longevity with improved adhesion and resistance properties.

Implementation Method 1

the print cartridges contain a series of tiny chambers, each containing a heater, which produce ink droplets from thermal vaporization of an ink solvent

Methodology Applied

Scientific EffectThermal vaporization: Evaporation

Implementation Method 2

a resistor is heated rapidly to produce a vapor bubble (hence the phrase 'bubble jet')

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 3

radiation curable inkjet ink compositions... exposing to electron beam radiation

Methodology Applied

Scientific EffectPhotopolymerization: Photopolymerisation

Data Source

PatentUS11479684B2Radiation curable inkjet ink compositions, printed articles, and thermal inkjet methods of using the same

Publication Date: 2022.10.25 KAO CORP

AI summary

A radiation curable inkjet ink composition that includes (A) a mono-ethylenically unsaturated oligomer, (B) a mono-ethylenically unsaturated monomer, and (C) a solvent, wherein the radiation curable inkjet ink composition is substantially free of a photoinitiator and wherein a total weight of the mono-ethylenically unsaturated oligomer (A) is less than or equal to the total weight of the mono-ethylenically unsaturated monomer (B). A printed article including the radiation curable inkjet ink composition in cured form, and a method of forming an image with a thermal inkjet printhead are also provided.