Pigment Dispersion Crosslinking for Stable Inkjet Jetting
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Solution Overview
Problem
Existing methods for producing pigment dispersions for inkjet inks do not adequately address the issue of dispersion stability, leading to instability in jetting stability and potential bleeding in image recording.
Innovation Solution
A method involving the production of a polymer dispersant with specific structural units and controlled neutralization and crosslinking steps to achieve a pigment dispersion with enhanced dispersion stability, resulting in improved jetting stability and reduced bleeding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polymer dispersants are used for pigment dispersion, then the pigment can be dispersed in the aqueous medium, but the dispersion stability is insufficient leading to jetting instability and bleeding
Solution Approach 1:
The patent applies parameter changes by carefully controlling the degree of neutralization of the polymer dispersant (maintaining carboxyl groups without complete neutralization) and controlling the acid value within specific ranges. This partial neutralization approach changes the chemical parameters of the dispersant to achieve optimal balance between water solubility and pigment binding, resulting in improved dispersion stability and jetting reliability without complete neutralization
Solution Approach 2:
The patent creates a composite system by combining the polymer dispersant with specific structural units (hydrophilic units from acrylic acid and hydrophobic units from long-chain alkyl esters) in defined ratios. This composite structure of the dispersant molecule, with both polar and non-polar regions, enables simultaneous interaction with aqueous medium and pigment particles, achieving stable dispersion that prevents jetting instability and bleeding
2Ease of operation
If the degree of neutralization is increased to improve water solubility, then the dispersant becomes more water-soluble, but the dispersion stability decreases and bleeding occurs
Solution Approach 1:
The patent applies partial action by deliberately avoiding complete neutralization of the polymer dispersant. Instead of fully converting carboxyl groups to carboxylate salts for maximum water solubility, the patent maintains partial unneutralized carboxyl groups (controlling acid value within specific ranges). This partial neutralization provides just enough water solubility while retaining sufficient pigment binding capability, preventing the dispersion instability and bleeding that would result from complete neutralization
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 method produces a pigment dispersion with excellent dispersion stability, ensuring stable jetting and suppressed bleeding in inkjet inks, thereby enhancing image recording quality.
Implementation Method 1
a crosslinking step of crosslinking the polymer dispersant B in the uncrosslinked dispersion after the acid addition step to obtain a polymer dispersant C
Implementation Method 2
a neutralization step of neutralizing a part of the acid group contained in the polymer dispersant N to obtain a polymer dispersant A having a degree of neutralization of less than 100%
Implementation Method 3
a dispersion step of dispersing a pigment in an aqueous medium by the polymer dispersant A to obtain an uncrosslinked dispersion
Data Source
Figure 1~2
AI summary
Provided are a method for producing a pigment dispersion, which is capable of producing a pigment dispersion having excellent dispersion stability of a pigment, and applications thereof. The method for producing a pigment dispersion that includes neutralizing a part of an acid group in a polymer dispersant which contains a (meth)acrylic acid ester unit containing an alkyl group having 10 or more carbon atoms and contains an acid group, dispersing a pigment with the neutralized polymer dispersant to obtain an uncrosslinked dispersion, adding an acid to the uncrosslinked dispersion, and then crosslinking the uncrosslinked dispersion, in which an acid value AV1 after the neutralization, an acid value AV2 after the crosslinking, a degree of neutralization ND1 after the neutralization, and a degree of neutralization ND2 after the acid addition in the polymer dispersant satisfy inequalities (1) and (2); and applications thereof are provided. 0.60≤AV1ND1−ND2/AV1−AV2≤2.00 0.30≤1−ND1/ND1−ND2≤5.00