Ink Composition Microcapsule Shell Cross-Linking Stability
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Solution Overview
Problem
The existing ink jet ink compositions suffer from low dispersion stability of pigments due to the presence of a large amount of low-molecular-weight compounds with dispersing groups, leading to degradation of ejectability and temporal stability during image recording.
Innovation Solution
An ink composition is developed with microcapsules having a three-dimensional cross-linked shell and a core, incorporating a colorant with an ionic group or a dispersant, and a controlled content ratio of acidic group-containing compounds with a molecular weight of 2000 or less, which enhances dispersion stability and ejectability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a large amount of low-molecular-weight compound with carboxy group is introduced into microcapsules by mixing at ordinary temperature, then the dispersing group is introduced into microcapsules, but the dispersibility of colorant such as pigment is degraded due to presence of free low-molecular-weight compound
Solution Approach 1:
The patent applies parameter changes by controlling the content ratio of acidic group-containing compounds to be 0.2 mass% or more and 0.45 mass% or less, and by conducting the mixing process at 50°C or higher (preferably 60°C or higher) rather than ordinary temperature. This temperature parameter change improves the efficiency of introducing dispersing groups into microcapsules while reducing the amount of free low-molecular-weight compounds, thereby resolving the contradiction between introducing sufficient dispersing groups and maintaining colorant dispersibility.
2Ease of operation
If low-molecular-weight compound with dispersing group is present in the ink, then dispersing effect is provided, but temporal stability of ink jet ink is degraded
Solution Approach 1:
The patent resolves this contradiction by changing the temperature parameter during the mixing process (50°C or higher, preferably 60°C or higher) and by precisely controlling the content ratio of acidic group-containing compounds (0.2-0.45 mass%). These parameter changes ensure adequate dispersing effect while minimizing the presence of free low-molecular-weight compounds that would otherwise degrade temporal stability.
3Ease of operation
If low-molecular-weight compound with carboxy group is present in the ink, then dispersing function is provided, but ejectability during recording is degraded
Solution Approach 1:
The patent applies parameter changes by conducting mixing at elevated temperatures (50°C or higher, preferably 60°C or higher) and by controlling the content ratio of acidic group-containing compounds within 0.2-0.45 mass%. This ensures the dispersing function is maintained through efficient incorporation of dispersing groups into microcapsules, while the reduced amount of free low-molecular-weight compounds prevents degradation of ejectability.
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 achieves high dispersion stability and improved temporal stability, maintaining the integrity of the ink during ejection and recording processes.
Implementation Method 1
a shell having a three-dimensional cross-linked structure comprising at least one of a urethane bond or a urea bond
Implementation Method 2
a colorant selected from the group consisting of a colorant having an ionic group and a colorant at least a part of a surface of which being covered with a dispersant having an ionic group
Data Source
Figure 1
Figure 2~3
AI summary
An ink composition including: a microcapsule having: a shell having a three-dimensional cross-linked structure including at least one of a urethane bond or a urea bond; and a core encapsulated by the shell; a colorant selected from the group consisting of a colorant having an ionic group and a colorant at least a part of a surface of which being covered with a dispersant having an ionic group; and water, a content ratio of an acidic group-containing compound having at least an acidic group, an acid dissociation constant of 5 or less, and a molecular weight of 2000 or less, relative to a total mass of the ink composition, is 0.5 mass% or less; an ink set, a method for producing an ink composition, and an image recording method.