Ink-Jet Ink Composition for High-Speed Plain Paper Stability

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Solution Overview

Problem

Ink-jet recording methods face challenges with ink ejection stability and dot diameter consistency, particularly when recording on plain paper, leading to insufficient fixability, resolution, and color forming density, especially at high speeds.

Innovation Solution

An ink-jet ink composition comprising a pigment, polymer pigment dispersant, polymer particles, hydrophilic organic solvent, water, and a water-soluble acidic compound or its salt with a molecular weight of 200 or less, formulated to improve ink ejection stability and reduce dot diameter differences between primary and secondary color dots.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If an ink composition containing pigment and polymer particles is used for high speed recording, then recording speed is improved, but ink ejection stability deteriorates

Engineering Contradiction:
Improverecording speedVSAvoidink ejection stability
Core Design Contradiction:
ProductivityVSReliability

Solution Approach 1:

The patent changes the chemical parameters of the ink composition by introducing a water-soluble acidic compound with specific molecular weight (200 or less) and controlling its concentration (50-1000 ppm). This parameter modification stabilizes the ink ejection process at high recording speeds by adjusting the charge characteristics of polymer particles, thereby resolving the contradiction between high productivity and reliability.

Inventive Principle:
Principle #35Parameter changes

2Manufacturing precision

If an ink composition with low molecular weight pigment dispersant is used, then dot diameter consistency is improved, but ink ejection stability deteriorates

Engineering Contradiction:
Improvedot diameter consistencyVSAvoidink ejection stability
Core Design Contradiction:
Manufacturing precisionVSReliability

Solution Approach 1:

The patent creates a composite ink system by combining pigment particles with polymer particles and a water-soluble acidic compound. This composite formulation works synergistically: the polymer particles provide bulk structure and stability, while the low molecular weight acidic compound fine-tunes the surface charge and dot diameter consistency, achieving both precision and reliability simultaneously.

Inventive Principle:
Principle #40Composite materials

3Ease of operation

If recording is performed on plain paper, then ease of operation is improved, but fixability and resolution deteriorate

Engineering Contradiction:
Improverecording medium compatibilityVSAvoidfixability and resolution
Core Design Contradiction:
Ease of operationVSManufacturing precision

Solution Approach 1:

The ink composition is designed to be self-adjusting for different recording conditions. The water-soluble acidic compound automatically modulates the charge state of pigment particles based on the recording medium properties, allowing the same ink formulation to perform optimally on various media including plain paper without requiring medium-specific formulation changes, thus achieving ease of operation with maintained precision.

Inventive Principle:
Principle #25Self-service

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 ink composition enhances ink ejection stability and reduces dot diameter differences, ensuring improved image quality and fixability even at high speeds, with optimal performance achieved within specific concentration ranges of the water-soluble acidic compound.

Implementation Method 1

it has been found that when a water-soluble acidic compound having a molecular weight of 200 or less and a salt of the water-soluble acidic compound are used, ink ejection stability can be improved and the dot diameter difference between a primary color dot and a secondary color dot can be reduced

Methodology Applied
Scientific EffectElectrostatic charge modification: Electrostatics

Implementation Method 2

an ink-jet ink composition comprising: a pigment, a polymer pigment dispersant, polymer particles

Methodology Applied
Scientific EffectElectrostatic repulsion: Electrostatics

Data Source

PatentUS8426496B2Ink-jet ink composition, ink set, and image forming method
Publication Date: 2013.04.23 FUJIFILM CORP

AI summary

An ink-jet ink composition comprising: a pigment, a polymer pigment dispersion, polymer particles, a hydrophilic organic solvent, water, and at least one of a water-soluble acidic compound having a molecular weight of 200 or less or a salt thereof in an amount of from 50 ppm to 1,000 ppm; an ink set that includes the ink-jet ink composition and a treatment liquid that forms an aggregate when contacted with the ink-jet ink composition; and an image forming method using the ink set.