Water-Based Ink Formulation for High Optical Density and Uniform Image Quality
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Solution Overview
Problem
Water-based inks for ink-jet recording face challenges in achieving high optical density and quick drying performance without compromising redispersibility and causing white stripe-shaped unevenness (banding) when the blending amount of self-dispersible pigment is increased or discharge amount is decreased.
Innovation Solution
A water-based ink formulation incorporating a self-dispersible pigment modified with a carboxylic acid group, di-2-ethylhexyl sulfosuccinic acid or its salt, and a compound represented by a specific general formula, which enhances optical density and suppresses white stripe-shaped unevenness while maintaining redispersibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the blending amount of self-dispersible pigment is increased to improve optical density, then the optical density increases, but the redispersibility of the water-based ink is lowered
Solution Approach 1:
The patent introduces a specific dispersant (di-2-ethylhexyl sulfosuccinic acid or its salt) as an intermediary substance that mediates between the self-dispersible pigment particles and the water-based ink medium. This dispersant acts as a bridge that maintains pigment dispersion stability even at high pigment concentrations, preventing aggregation while preserving redispersibility after drying. The dispersant molecules adsorb onto pigment surfaces and provide steric and electrostatic stabilization, enabling high optical density without sacrificing redispersibility.
Solution Approach 2:
The patent optimizes the concentration ratio between the dispersant (di-2-ethylhexyl sulfosuccinic acid or its salt) and the self-dispersible pigment within specific ranges (0.1-5 wt% dispersant relative to pigment, with optimal ratios of 0.2-2 wt%). By precisely controlling these compositional parameters, the ink formulation achieves a balance where sufficient pigment is present for high optical density while adequate dispersant is maintained to preserve redispersibility and prevent aggregation.
2Speed
If the discharge amount of water-based ink is decreased to achieve quick drying performance, then the drying speed increases, but white stripe-shaped unevenness (banding) appears on the recorded image
Solution Approach 1:
The patent optimizes multiple parameters simultaneously: the dispersant-to-pigment ratio (0.1-5 wt%, optimally 0.2-2 wt%), pigment particle size distribution (D50: 0.01-0.1 μm, D90: 0.05-0.2 μm), and ink composition ratios. These parameter optimizations ensure uniform ink discharge characteristics and consistent pigment distribution on the recording medium, preventing banding even when discharge amounts are reduced for quick drying performance.
Solution Approach 2:
The patent creates a composite ink formulation that combines self-dispersible pigment, water, di-2-ethylhexyl sulfosuccinic acid or its salt, and a specific compound (formula 1) in optimized proportions. This composite formulation ensures uniform flow and discharge characteristics while maintaining quick drying performance, as the synergistic interaction between components provides both rapid evaporation and uniform pigment deposition without banding.
3Illumination intensity
If the blending amount of self-dispersible pigment is increased to improve optical density, then the optical density increases, but white stripe-shaped unevenness (banding) appears when discharge amount is decreased
Solution Approach 1:
The dispersant (di-2-ethylhexyl sulfosuccinic acid or its salt) acts as an intermediary that enables high pigment loading while maintaining uniform discharge characteristics. The dispersant prevents pigment aggregation and ensures homogeneous distribution throughout the ink, allowing high optical density to be achieved without the banding that would normally result from decreased discharge amounts.
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 formulation allows for increased optical density and suppressed white stripe-shaped unevenness, even with higher self-dispersible pigment levels, without lowering redispersibility, and ensures stable ink discharge and image quality.
Implementation Method 1
a self-dispersible pigment modified with carboxylic acid group; water
Implementation Method 2
di-2-ethylhexyl sulfosuccinic acid or salt thereof
Data Source
AI summary
A water-based ink for ink-jet recording includes a self-dispersible pigment modified with carboxylic acid group; water; di-2-ethylhexyl sulfosuccinic acid or salt thereof; and a compound represented by the following general formula (1):