Recirculating Inkjet Fluid Stability via Polyurethane Binder
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Solution Overview
Problem
Pigment-based inks for inkjet printing face challenges such as instability, filter plugging, and poor durability due to large pigment particle sizes, incomplete polymer binder film formation, and high water content, which affect abrasion resistance and jetting performance in continuous inkjet systems.
Innovation Solution
Aqueous polyurethane binder with a specific molecular structure is used in the printing fluid, providing improved abrasion resistance and stability, allowing for extended recirculation without fluid destabilization or filter clogging, and enabling high-frequency jetting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pigment particles are reduced to sub-micron size for improved optical density and gloss, then manufacturing complexity increases due to lengthy milling operations, but image quality improves
Solution Approach 1:
The patent changes the particle size parameter of pigment to sub-micron range (specifically 0.1-1.0 micrometers) to achieve optimal optical density and gloss while maintaining colloidal stability in the ink formulation
Solution Approach 2:
The patent performs preliminary milling operations to reduce pigment particles to the required sub-micron size before ink formulation, ensuring proper particle size distribution is achieved in advance to prevent later manufacturing issues
2Strength
If pigmented ink is formulated with polymers and dispersants to improve abrasion resistance, then image durability improves, but fluid stability deteriorates during recirculation
Solution Approach 1:
The patent optimizes the molecular weight of polyurethane polymer to 6,000-50,000 and controls pigment particle size at 0.1-1.0 micrometers, creating a balance where the polymer provides sufficient abrasion resistance while maintaining fluid stability during recirculation
Solution Approach 2:
The patent creates a composite ink formulation combining pigment particles, polyurethane polymer, and dispersants in specific proportions, where each component works synergistically to provide both durability and stability
3Productivity
If high water content is used in ink formulation for optimal firing performance, then jetting performance improves, but image durability worsens due to incomplete binder film formation
Solution Approach 1:
The patent optimizes water content and humectant levels to achieve optimal firing performance while controlling the evaporation rate to allow complete binder film formation, balancing jetting performance with image durability
4Productivity
If recirculation system is implemented to improve productivity, then printing efficiency improves, but filter plugging occurs due to pigment aggregation
Solution Approach 1:
The patent uses dispersants as intermediary substances that prevent pigment particle aggregation during recirculation, keeping particles suspended and preventing filter plugging while maintaining printing efficiency
Solution Approach 2:
The patent controls pigment particle size at 0.1-1.0 micrometers and optimizes polymer concentration to prevent aggregation during recirculation, ensuring reliable filter operation while maintaining high printing efficiency
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 solution enhances the durability and stability of printed images, reduces filter plugging, and maintains fluid stability during recirculation, supporting continuous inkjet printing operations with improved image quality and system reliability.
Implementation Method 1
As the ink contacts the receiver, some of the components penetrate into the receiver and the droplets can simultaneously spread laterally on the receiver surface. Carrier fluids such as water and humectants are drawn into the receiver by capillary forces and the polymer binders begin to film form.
Implementation Method 2
Carrier fluids such as water and humectants are drawn into the receiver by capillary forces and the polymer binders begin to film form.
Implementation Method 3
Humectants can have the effect of plasticizing the polymer binder and making the surface of the image tacky or softer than if no humectant was present.
Data Source
AI summary
A printing system for applying a printing fluid to a substrate, comprising a printing fluid applicator and a recirculating printing fluid supply supplying printing fluid to the applicator, wherein the printing fluid comprising water and a water dispersible polyurethane additive of the general formula of (I)wherein Z is the central portion of a monomer unit that is the polymerization product of a diisocyanate; X1—Y1—X1 represents one or more soft segments wherein Y1 represents the central portion of a unit that is the polymerization product of a diamine or diol prepolymer having a molecular weight of greater than 300 Daltons; W is the central portion of one or more units containing an acid group; X2—Y2—X2 represents one or more hard segments wherein Y2 represents the central portion of a unit that is the polymerization product of a C2-C8 diol or diamine having a molecular weight of less than 250 Daltons; and X1, V and X2 can be the same or different and are an —O— or —N— atom; and further wherein the polyurethane additive has a weight average molecular weight of at least 6,000 Daltons and a sufficient number of acid groups to provide an acid number greater than 35, and the one or more X2—Y2—X2 hard segments are present at from 1 wt % to less than 13 wt % of the polyurethane additive.