Amphoteric Block Copolymer Dispersant for Inkjet Pigment Stability
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Solution Overview
Problem
Current inkjet inks and printing methods face challenges in achieving optimal print quality and jetting reliability, particularly in maintaining dispersion stability of carbon black pigments, which is crucial for high optical density and color accuracy.
Innovation Solution
The development of an aqueous inkjet ink using an amphoteric polymeric dispersant as a block copolymer, comprising an A block of amine monomers and a B block of acidic and hydrophobic monomers, which is neutralized and optimized for pH sensitivity to enhance pigment dispersion stability and interaction with reactive inks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional dispersants are used to stabilize carbon black pigment, then dispersion stability is improved, but print quality and jetting reliability cannot be optimized simultaneously
Solution Approach 1:
The patent applies parameter changes by developing a block copolymer dispersant with specific molecular weight (Mn 2000-16000) and controlled amine-to-acid ratio (0.5-3.0), where the amine block contains 2-16 units and acid block contains 4+ units. This precise parameter control enables the dispersant to maintain pigment stability while ensuring optimal jetting performance through balanced electrostatic and steric stabilization mechanisms.
Solution Approach 2:
The invention uses a composite block copolymer structure combining amine-containing blocks (2-16 units) and acid-containing blocks (4+ units) with hydrophobic monomers. This composite structure provides dual functionality: the amine blocks stabilize basic pigments through electrostatic repulsion while the acid blocks provide steric stabilization and control intercolor bleed, achieving both dispersion stability and jetting reliability simultaneously.
2Stability of the object's composition
If pigment dispersion stability is enhanced for high optical density, then color accuracy is improved, but intercolor bleed control deteriorates
Solution Approach 1:
The patent applies local quality by creating distinct functional blocks within the dispersant molecule: the amine-containing blocks (2-16 units) provide localized electrostatic stabilization for high optical density, while the separate acid-containing blocks (4+ units) provide localized steric stabilization for intercolor bleed control. This spatial separation of functions within the single dispersant molecule resolves the contradiction between these two requirements.
Solution Approach 2:
The invention controls the amine-to-acid ratio parameter (0.5-3.0) to balance two opposing functions: higher amine content enhances pigment stabilization for optical density, while sufficient acid content maintains steric barriers against intercolor bleed. This parameter optimization allows simultaneous achievement of both goals.
3Stability of the object's composition
If block copolymer dispersants with amine and acidic monomers are used, then dispersion stability is improved, but structural complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the dispersant into distinct functional blocks: amine-containing blocks (2-16 units) and acid-containing blocks (4+ units) with specific hydrophobic monomers. This segmented architecture provides clear functional separation while maintaining a relatively simple overall structure that is easier to synthesize and characterize compared to random copolymers with the same functionality.
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
This solution improves print quality by maintaining stable pigment dispersion, reducing intercolor bleed, and achieving better optical density and chroma, while ensuring reliable jetting performance.
Implementation Method 1
amphoteric polymeric dispersant which is a block copolymer comprising an A block and a B block wherein the A block is a segment consisting essentially of an amine monomer... and the B block is a segment comprising an acidic monomer
Implementation Method 2
block copolymer dispersants which are described, for example, in U.S. Pat. Nos. 5,085,698, 5,519,085, 5,272,201, and 5,648,405
Implementation Method 3
wherein the dispersant is neutralized, and the B block is free of an amine monomer
Data Source
AI summary
The present disclosure provides a ink-jet ink, having a pH greater than 7, comprising a first aqueous vehicle, a colorant, more typically a carbon black pigment, and an amphoteric polymeric dispersant, wherein the amphoteric polymeric dispersant is a block copolymer comprising an A block and a B block, wherein the A block is a segment consisting essentially of an amine monomer; and the B block is a segment comprising an acidic monomer and at least one hydrophobic monomer; wherein the dispersant is neutralized, and the B block is free of an amine monomer. The disclosure further pertains to an ink set comprising this ink jet ink and at least a second ink which contains a reactive species with appropriate cationic agent, salt, or pH modifying agent capable of destabilizing the colorant containing dispersion of the first ink. Still further, the disclosure pertains to a method of printing wherein the first ink and second ink of the ink set are printed in an adjacent relationship, thereby minimizing penetration, feathering and/or bleed of the colorant and improving print quality.