Modified Pigment Inkjet Ink Conductivity Control
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Solution Overview
Problem
Existing inkjet ink compositions, particularly those for piezo printers using shear mode printheads, face challenges with high conductivity issues that affect performance, necessitating the development of modified pigments with improved properties to maintain low conductivity levels over time.
Innovation Solution
The use of modified pigments with attached geminal bisphosphonic acid groups or their partial esters, featuring a quaternary ammonium counterion, in combination with a cosolvent, to form inkjet ink compositions that exhibit reduced conductivity increases, even after thermal aging, by ion exchanging the counterion and optionally heat aging the dispersion to remove desorbed ions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional modified pigments are used in inkjet ink compositions, then good overall performance properties are achieved, but conductivity increases over time which affects performance in piezo printers
Solution Approach 1:
The patent changes the chemical parameter of the counterion attached to the geminal bisphosphonic acid groups on the pigment surface. Specifically, it uses quaternary ammonium counterions with different alkyl chain lengths (C1-C6) to modify the conductivity behavior. This parameter change results in ink compositions that maintain low conductivity levels over time while preserving good performance properties
Solution Approach 2:
The patent creates a composite structure by attaching geminal bisphosphonic acid groups with quaternary ammonium counterions to the pigment surface. This composite modification combines the pigment core with functional organic groups that have specific conductivity-control properties, resulting in a material that maintains low conductivity while providing good inkjet performance
2Reliability
If pigments with attached functional groups are used to improve performance, then ink composition performance is enhanced, but conductivity remains too high for piezo printer requirements
Solution Approach 1:
The patent specifically changes the counterion parameter from conventional options to quaternary ammonium ions with alkyl chains of C1-C6 length. This parameter modification is critical as it enables the pigment to maintain low conductivity levels (below 1000 microsiemens/cm) while still providing the performance benefits of functional group attachment
Solution Approach 2:
The patent uses short-chain quaternary ammonium counterions (C1-C6) that provide sufficient functionality without causing excessive conductivity. These short-chain counterions effectively provide the necessary performance enhancement while minimizing the harmful conductivity effect, acting as an efficient but limited-duration solution
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 resulting inkjet ink compositions demonstrate stable low conductivity, with values below 1000 microsiemens/cm at 10-15% modified pigment content, remaining consistent after 4 weeks at 60°C, effectively addressing the conductivity challenges faced by piezo inkjet printing.
Implementation Method 1
ion exchanging the counterion of the modified pigment to form an aqueous dispersion of a modified pigment comprising a pigment having attached at least one salt of a geminal bisphosphonic acid group or partial esters thereof having a corresponding quaternary ammonium counterion
Data Source
AI summary
The present invention relates to a modified pigment comprising a pigment having attached at least one salt of a geminal bisphosphonic acid group or partial esters thereof, as well as to dispersions and inkjet ink compositions comprising such modified pigments. Preferably the salt comprises a quaternary ammonium counterion.