Smear-Resistant Inkjet Inks Using Polyurethane Dispersion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional inkjet inks using self-dispersed pigments suffer from poor fixation and smear resistance when printed on plain paper, leading to issues with color development and ejection stability.
Innovation Solution
Development of aqueous inkjet inks comprising self-dispersed pigments and polyurethane dispersions with specific thermal properties, such as a glass transition temperature between −30° C. and 35° C., loss modulus of 1.7 to 5×10^8 pascals, and peak tan delta of 0.23 to 0.65, which enhance smear-fastness, water-fastness, and optical density while maintaining stability and jetting characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If self-dispersed pigments are used in aqueous inkjet inks, then dispersion stability and viscosity are improved, but fixation and smear resistance deteriorate when printed on plain paper
Solution Approach 1:
A polyol penetrant is introduced as an intermediary substance between the self-dispersed pigment and the plain paper substrate. The penetrant modifies the interaction interface, enabling the pigment to achieve both good dispersion stability in the aqueous medium and adequate fixation on the paper surface without requiring additional heating or UV curing steps
Solution Approach 2:
The chemical composition and physical properties of the ink formulation are modified by adding specific polyol penetrants with controlled molecular weight, hydroxyl value, and polarity. These parameter changes enable the ink to maintain dispersion stability while improving fixation and smear resistance on plain paper
2Illumination intensity
If pigment content is increased to improve color development, then optical density is improved, but viscosity increases and ejection stability deteriorates
Solution Approach 1:
The polyol penetrant acts as a mediator that reduces the interaction between pigment particles, preventing aggregation even at high pigment concentrations. This allows the formulation to achieve high optical density while maintaining low enough viscosity for stable ejection
Solution Approach 2:
The ink formulation is designed as a composite system combining self-dispersed pigment, aqueous medium, and polyol penetrant in specific ratios. This composite approach allows optimization of both color development and flow properties that cannot be achieved with simple pigment-water mixtures
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 inkjet inks demonstrate improved smear resistance, water-fastness, and optical density, maintaining stability and jetting performance, even when subjected to highlighter tests, without requiring additional fixation steps like heat or UV curing.
Implementation Method 1
Polyurethane dispersions having glass transition temperatures (Tg) of greater than −30° C. to less than 35° C. provide good smear resistance.
Implementation Method 2
The self dispersed pigment optionally comprises anionic hydrophilic chemical groups, and optionally, the chemical groups comprise carboxyl groups. These anionic hydrophilic groups may be obtained by oxidatively treating the surface with hypochlorous acid, sulfonic acid, or ozone
Data Source
AI summary
Inkjet inks are provided, relating in particular to smear resistant inkjet inks, and even more particularly to smear resistant pigmented aqueous inkjet inks comprising polyurethane dispersions and self-dispersing pigments. The polyurethane dispersions have a glass transition temperature Tg greater than −30 ° C. to less than about 35 ° C. and have at least one of the following thermal properties: loss modulus E″ of 1.7 to 5×108 pascals, and/or a peak tan delta is 0.23 to 0.65, where the glass transition temperature, peak tan delta and the loss modulus are measured by dynamic mechanical analysis on a film prepared from the polyurethane dispersion.