Colored Particle Dispersion for Ink-Jet Ejection Stability
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Solution Overview
Problem
Ink-jet printing on low-water absorbing printing media faces issues with prolonged drying times, deterioration in rub fastness, and pigment deposition, leading to insufficient ejection stability and alcohol resistance in existing water-based inks.
Innovation Solution
A colored fine particle dispersion is produced by subjecting a monomer mixture containing an acid group-containing polymerizable monomer to emulsion polymerization in the presence of a pigment, with a neutralizing agent containing a water-soluble amine compound, resulting in a pH value of 6 to 11, which enhances ejection stability and alcohol resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If water-based ink is used for ink-jet printing on low-water absorbing printing media, then ease of operation and environmental friendliness are improved, but drying time is prolonged and rub fastness deteriorates
Solution Approach 1:
The invention changes the chemical parameters of the ink composition by incorporating specific resin particles with controlled particle size distribution (average 0.1-10 μm, with 80% or more being 0.1-1 μm) and chemical composition (carboxyl group-containing polymer). These parameter changes enable the ink to maintain water-based formulation while achieving rapid drying and good rub fastness on low-water absorbing media.
Solution Approach 2:
The invention uses a composite ink formulation combining water, specific resin particles (carboxyl group-containing polymer), and pigment particles. This composite material approach allows the ink to exhibit both the environmental benefits of water-based ink and the performance characteristics of solvent-based inks, including rapid drying and excellent rub fastness on challenging substrates.
2Reliability
If pigment is used as colorant to improve weathering and water resistance, then durability is improved, but pigment deposition on non-liquid absorbing media increases causing rub fastness deterioration
Solution Approach 1:
The invention introduces resin particles as an intermediary between the pigment and the printing medium. These resin particles (with carboxyl groups and specific size distribution) act as binding agents that hold pigment particles together, preventing direct pigment deposition on the non-liquid absorbing media. This intermediary layer maintains weathering resistance while eliminating the harmful pigment deposition effect.
3Strength
If resin particles with film-forming capability are incorporated to improve rub fastness, then adhesion is improved, but storage stability deteriorates due to particle aggregation
Solution Approach 1:
The invention precisely controls the particle size parameters of the resin particles, specifying that 80% or more of particles should be in the 0.1-1 μm range. This parameter control prevents excessive aggregation while maintaining film-forming capability. The carboxyl group content is also controlled (0.1-10 mmol/g) to balance adhesion and storage stability.
Solution Approach 2:
The invention creates local quality differences in the resin particle structure by controlling the distribution of carboxyl groups and the particle size distribution. The small particle size (0.1-1 μm) provides good dispersion and storage stability, while the carboxyl groups provide local adhesion sites for pigment binding and substrate attachment, achieving both rub fastness and storage stability.
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 provides a water-based ink with improved ejection stability and alcohol resistance when printed on low-water absorbing media, maintaining storage stability and preventing viscosity increase during evaporation.
Implementation Method 1
the colored fine particles are produced by subjecting a monomer mixture containing an acid group-containing polymerizable monomer to emulsion polymerization in the presence of a pigment
Implementation Method 2
the neutralizing agent contains a water-soluble amine compound, and the colored fine particle dispersion has a pH value of not less than 6 and not more than 11
Data Source
AI summary
The present invention relates to [1] a colored fine particle dispersion containing colored fine particles and a neutralizing agent, in which the colored fine particles are produced by subjecting a monomer mixture containing an acid group-containing polymerizable monomer to emulsion polymerization in the presence of a pigment; the neutralizing agent contains a water-soluble amine compound; and the colored fine particle dispersion has a pH value of from 6 to 11, and [2] a process for producing a colored fine particle dispersion containing colored fine particles and a neutralizing agent, said process including the step 1 of subjecting a monomer mixture containing an acid group-containing polymerizable monomer to emulsion polymerization in the presence of a pigment to obtain a colored fine particle dispersion (p); and the step 2 of mixing the colored fine particle dispersion (p) and the neutralizing agent containing a water-soluble amine compound to obtain the colored fine particle dispersion having a pH value of from 6 to 11. The colored fine particle dispersion of the present invention is used in a water-based ink so that the resulting water-based ink is excellent in ejection stability upon evaporation of water from the ink system while maintaining excellent storage stability thereof, and it is possible to obtain printed materials that are excellent in alcohol resistance even when printed on a low-water absorbing printing medium.