Ink Composition Viscosity Stability via Divalent Metal Ion Control
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Solution Overview
Problem
Inkjet recording technologies face challenges with ink compositions that experience viscosity decrease over time, leading to reduced jetting stability and accuracy due to the separation of non-cross-linked polymers, which affects the ejection of ink droplets and their landing precision on recording media.
Innovation Solution
An ink composition is developed that includes a cross-linked polymer-coated pigment with a specific amount of divalent metal ions (30-200 ppm) and a free polymer with anionic groups, which helps maintain viscosity stability by inhibiting the transformation of free polymers, ensuring consistent jetting performance and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the viscosity of ink is decreased to reduce nozzle clogging, then the ease of operation is improved, but the jetting stability deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the concentration of divalent metal ions (30-200 ppm) and the acid value of the free polymer (95 mgKOH/g or more) to achieve the optimal balance between low viscosity for nozzle flow and sufficient stability for jetting performance. This quantitative parameter control resolves the contradiction between ease of operation and jetting stability.
2Duration of action of stationary object
If the ink composition is stored for long term, then the duration of action is improved, but the viscosity decreases due to polymer separation, worsening the jetting stability
Solution Approach 1:
The patent applies preliminary anti-action by pre-addling divalent metal ions to the ink composition before storage. These metal ions proactively inhibit the separation and precipitation of the free polymer during storage, preventing the viscosity decrease that would otherwise occur over time. This preemptive measure maintains jetting stability throughout the storage period.
Solution Approach 2:
The divalent metal ions act as an intermediary substance that mediates between the free polymer and the aqueous medium. The metal ions interact with the anionic groups of the polymer, forming a stable complex that prevents polymer aggregation and precipitation during storage, thereby maintaining consistent viscosity and jetting stability over time.
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 excellent jetting stability and reliability by preventing viscosity decrease, allowing for precise control of ink droplet amount and accurate landing on the recording medium, even after long-term storage, thereby enhancing image quality and reducing dot loss during high-speed image formation.
Implementation Method 1
the ink composition includes at least one divalent metal ion in an amount of from 30 ppm to 200 ppm with respect to the total mass of the ink composition and wherein the free polymer comprises an anionic group
Data Source
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AI summary
The present invention provides an ink composition having excellent jetting stability, which contains water, a cross-linked polymer-coated pigment in which at least a portion of a surface of the pigment is covered with a cross-linked polymer, a free polymer that is not bound to the cross-linked polymer-coated pigment, and at least one divalent metal ion in an amount of from 30 ppm to 200 ppm with respect to the total mass of the ink composition, and an ink set and an image forming method using the same, which are excellent in jetting stability.