Inkjet Ink Thixotropy Control for Image Quality and Ejection
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Solution Overview
Problem
Inkjet inks face challenges in maintaining good ejection performance and forming high-quality images, particularly on non-absorbent substrates, due to issues like thread-like defects and color bleeding, which existing methods struggle to address effectively.
Innovation Solution
The development of an inkjet ink with a thixotropy-imparting agent that maintains a viscosity of 15 mPa·s or less at high shear rates and 150 mPa·s or more at low shear rates, along with specific rheological properties, ensures smooth circulation and high viscosity upon landing, preventing defects and improving image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the platen is heated to high temperature to instantly dry and thicken the solvent, then image quality is improved by preventing bleeding, but ink adhesion around the head occurs resulting in poor ejection performance
Solution Approach 1:
The invention changes the rheological parameters of the ink by adding a thixotropy-imparting agent, transforming the ink's viscosity characteristics from temperature-dependent to shear-rate-dependent. This allows the ink to maintain low viscosity during ejection (high shear) and high viscosity during deposition (low shear), eliminating the need for high-temperature platen heating and thus preventing ink adhesion to the head while maintaining image quality.
Solution Approach 2:
The invention replaces the thermal field (heating system) with a rheological field (thixotropy control). Instead of using heat to control ink viscosity and prevent bleeding, the invention uses thixotropic agents to create shear-dependent viscosity, where the ink naturally transitions from low viscosity during circulation/ejection to high viscosity upon deposition, achieving the same image quality improvement without the harmful thermal effects.
2Manufacturing precision
If thixotropy is added to the ink to increase viscosity at low shear, then image quality is improved by preventing absorption, but ejection performance deteriorates due to high viscosity in the circulation system
Solution Approach 1:
The invention modifies the ink's viscosity parameters by introducing thixotropy, creating a non-Newtonian fluid whose viscosity dynamically changes with shear rate. The ink is formulated to have viscosity of 150 mPa·s or more at low shear rates (during deposition) for high-quality image formation, while maintaining viscosity of 15 mPa·s or less at high shear rates (during ejection) for reliable performance.
3Manufacturing precision
If ink viscosity is increased to prevent absorption by substrate, then image quality is improved, but ejection performance deteriorates due to high viscosity
Solution Approach 1:
The invention makes the ink's viscosity dynamic rather than static by incorporating thixotropic agents. The viscosity automatically adjusts based on the operational state: low viscosity (15 mPa·s or less) during high-shear ejection for reliable performance, and high viscosity (150 mPa·s or more) at low shear during deposition for high-quality image formation without excessive absorption.
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 approach enables the inkjet ink to maintain good ejection performance and form high-quality images by controlling viscosity and preventing ink adhesion, reducing ejection defects and enhancing image quality on non-absorbent substrates.
Implementation Method 1
a thixotropy-imparting agent, having a viscosity at 25° C. at a shear rate of 1000 (1/s) of 15 mPa·s or less, and a viscosity at 25° C. at a shear rate of 1 (1/s) of 150 mPa·s or more in a state where the aqueous solvent is removed from the inkjet ink so that a mass is 80% of an initial mass of the inkjet ink
Data Source
AI summary
An inkjet ink contains an aqueous solvent, a pigment, and thixotropy-imparting agent, having a viscosity at 25° C. at a shear rate of 1000 (1/s) of 15 mPa·s or less, and a viscosity at 25° C. at a shear rate of 1 (1/s) of 150 mPa·s or more in a state where the aqueous solvent is removed from the inkjet ink so that a mass is 80% of an initial mass of the inkjet ink.