Oil-Based Inkjet Ink Dispersant for Pigment Aggregation Control

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Solution Overview

Problem

Oil-based inkjet inks tend to form aggregates when exposed to external forces, such as sliding in ink pathways, due to increased cohesive forces around pigments with free acidic groups, leading to instability and printing issues.

Innovation Solution

The use of a dispersant formed with an acidic resin, a low-molecular weight amine compound, and a basic polymer in oil-based inkjet inks, which bonds with the acidic groups to reduce free acidic groups and prevent pigment aggregation, thereby stabilizing the ink.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If pigment with free acidic groups is used in oil-based inkjet ink, then color strength and pigment loading are improved, but aggregate formation increases under external forces

Engineering Contradiction:
Improvepigment loadingVSAvoidink stability
Core Design Contradiction:
Quantity of substanceVSStability of the object's composition

Solution Approach 1:

A dispersant comprising a basic polymer and a low-molecular-weight amine compound is introduced as an intermediary substance between the pigment particles and the ink medium. The basic polymer provides steric stabilization while the low-molecular-weight amine compound neutralizes free acidic groups on pigment surfaces through chemical bonding. This dual-component dispersant system effectively prevents aggregate formation by simultaneously addressing both steric and electrostatic stabilization needs, allowing high pigment loading while maintaining ink stability under external forces such as shear stress in ink pathways.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Stability of the object's composition

If dispersant is added to prevent pigment aggregation, then ink stability is improved, but ink composition complexity increases

Engineering Contradiction:
Improveink stabilityVSAvoidink composition
Core Design Contradiction:
Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The dispersant system merges two functional components into a single coordinated agent: a basic polymer providing steric stabilization and a low-molecular-weight amine compound neutralizing acidic groups. This combined approach achieves effective pigment dispersion and aggregation prevention while maintaining relatively simple ink composition. The synergistic interaction between the two dispersant components allows for effective stabilization without requiring multiple separate additives, thus balancing ink stability improvement with composition simplicity.

Inventive Principle:
Principle #5Merging (Combining)

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 effectively reduces the formation of aggregates in oil-based inkjet inks even under external forces, enhancing jetting stability and storage stability by maintaining pigment dispersion, resulting in improved image quality and print performance.

Implementation Method 1

a dispersant formed with an acidic resin, a low-molecular weight amine compound and a basic polymer

Methodology Applied
Scientific EffectChemical bonding: Chemical Bonding

Implementation Method 2

bonds with the acidic groups to reduce free acidic groups and prevent pigment aggregation

Methodology Applied
Scientific EffectAdsorption: Adsorption

Implementation Method 3

a dispersant formed with an acidic resin, a low-molecular weight amine compound and a basic polymer

Methodology Applied
Scientific EffectSteric stabilization:

Implementation Method 4

removing water from the water-in-oil emulsion to obtain a dispersant dispersion

Methodology Applied
Scientific EffectEvaporation: Evaporation

Data Source

PatentUS11542402B2Oil-based inkjet ink, method for producing oil-based inkjet ink and method for producing dispersant
Publication Date: 2023.01.03 RISO KAGAKU CORP

AI summary

An oil-based inkjet ink is disclosed that contains a pigment, a dispersant formed with an acidic resin, a low-molecular weight amine compound and a basic polymer, and a non-aqueous solvent. A method for producing an oil-based inkjet ink and a method for producing a dispersant is also disclosed.