Water-Based Ink Sedimentation Control via Pigment Size Ratio
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Solution Overview
Problem
Water-based inks for ink-jet recording using self-dispersible pigments face issues with sedimentation, leading to increased viscosity and unsatisfactory jetting due to pigment settling, particularly with black pigments.
Innovation Solution
A water-based ink formulation incorporating a self-dispersible black pigment and resin-dispersed chromatic pigments, such as magenta and cyan, with a specific mass ratio and particle size differential to suppress sedimentation, maintaining a liquid color similar to inks containing only self-dispersible black pigment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If self-dispersible black pigment is used in water-based ink, then the ink can be formulated without additional dispersants, but the pigment particles sediment over time causing increased viscosity and unsatisfactory jetting
Solution Approach 1:
The patent introduces resin-dispersed chromatic pigments as intermediary substances that interact with the self-dispersible black pigment. These chromatic pigments with smaller particle diameters act as mediators that prevent the aggregation and sedimentation of black pigment particles, thereby maintaining stable jetting performance while keeping the formulation relatively simple.
Solution Approach 2:
The patent controls the particle diameter parameter of chromatic pigments to be smaller than that of black pigment (specifically, the ratio of mean particle diameter of chromatic pigment to black pigment is 0.05 to 0.5). This parameter change in particle size distribution prevents sedimentation by creating a more uniform dispersion where smaller chromatic particles fill spaces between larger black particles, reducing overall settling tendency.
2Reliability
If chromatic pigments are added to suppress black pigment sedimentation, then jetting stability improves, but the liquid color may deviate from the desired profile
Solution Approach 1:
The patent precisely controls the particle diameter ratio parameter between chromatic and black pigments (0.05 to 0.5) and the mass ratio parameter (0.01 to 0.5) to achieve the desired balance. By optimizing these parameters, the chromatic pigments suppress sedimentation effectively while their minimal quantity and small size ensure they do not significantly alter the liquid color, which remains dominated by the black pigment.
Solution Approach 2:
The patent applies local quality by using chromatic pigments with specific functional properties (small particle size, resin dispersion) only where needed for sedimentation control, rather than uniformly throughout the formulation. The chromatic pigments are dispersed at low concentrations specifically to address the sedimentation issue without broadly affecting the overall color profile.
3Manufacturing precision
If chromatic pigments are used to maintain liquid color, then color accuracy improves, but sedimentation of black pigment increases due to inappropriate particle size ratio
Solution Approach 1:
The patent identifies and controls the critical parameter of particle diameter ratio between chromatic and black pigments (0.05 to 0.5). This parameter change is essential because smaller chromatic particles create a more stable dispersion structure that prevents black pigment sedimentation. The optimized particle size distribution ensures both color accuracy and compositional stability.
Solution Approach 2:
The patent creates a composite pigment system combining self-dispersible black pigment with resin-dispersed chromatic pigments. This composite approach leverages the complementary properties of different pigment types and sizes to achieve both color accuracy and enhanced dispersion stability, where the chromatic pigment component actively contributes to preventing black pigment aggregation.
4Reliability
If the mass ratio of chromatic to black pigment is increased to suppress sedimentation, then jetting stability improves, but the liquid color deviates more from the desired profile
Solution Approach 1:
The patent optimizes the mass ratio parameter of chromatic to black pigment (0.01 to 0.5) to find the optimal balance point. Within this range, sufficient chromatic pigment is present to suppress sedimentation through steric hindrance and dispersion stabilization, while the quantity remains low enough to preserve the dominant black color profile and achieve accurate liquid color.
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 sedimentation of self-dispersible black pigment, ensuring stable ink flow and maintaining a color profile close to that of inks with only self-dispersible black pigment, while preventing excessive viscosity that could hinder jetting.
Implementation Method 1
a resin-dispersed chromatic pigment including a resin-dispersed magenta pigment and a resin-dispersed cyan pigment
Implementation Method 2
self-dispersible black pigment
Data Source
AI summary
There is provided a water-based ink for ink-jet recording including: a self-dispersible black pigment; a resin-dispersed chromatic pigment including a resin-dispersed magenta pigment and a resin-dispersed cyan pigment; and water. A ratio (Col/Bk) of a solid content mass (Col) of the resin-dispersed chromatic pigment to a solid content mass (Bk) of the self-dispersible black pigment is in a range of 0.24 to 0.73 and a mean particle diameter of the self-dispersible black pigment is greater than a mean particle diameter of the resin-dispersed chromatic pigment.