Ink Composition for High Pigment Inkjet Recording
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Solution Overview
Problem
Current inkjet recording methods face challenges in achieving high pigment concentration with excellent discharge, storage, and curing stability while maintaining low running costs and noise levels, particularly in comparison to electrophotographic and thermal transfer systems.
Innovation Solution
An ink composition comprising a pigment, a cationically polymerizable compound, and a photo-acid generator, where the pigment is copper phthalocyanine, azo, or quinacridone, and the cationically polymerizable compound is an oxirane or oxetane compound, optimized for high viscosity and polyfunctional monomers, along with a hindered amine compound for improved stability and curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pigment concentration is increased to reduce running costs and improve image quality, then image quality and cost efficiency are improved, but discharge stability and storage stability deteriorate
Solution Approach 1:
The patent changes the chemical parameters of the ink composition by introducing a specific cationically polymerizable compound with low viscosity (≤12 mPa·s) and high polyfunctionality (60-100 wt% polyfunctional monomers). This parameter change allows the formulation to maintain discharge stability even at high pigment concentrations (3.5-20 wt%) by optimizing the balance between pigment loading and ink fluidity.
Solution Approach 2:
The patent creates a composite ink system combining pigment particles with a specifically designed cationic polymerizable compound matrix. The composite nature of this system, where the low-viscosity compound acts as both solvent and polymer precursor, enables simultaneous achievement of high pigment concentration and stable discharge performance through synergistic interactions between components.
2Loss of substance
If pigment concentration is increased to reduce running costs, then running cost is reduced, but storage stability deteriorates
Solution Approach 1:
The patent modifies the viscosity parameter of the cationic polymerizable compound to be ≤12 mPa·s, which is significantly lower than conventional formulations. This parameter change prevents pigment aggregation and sedimentation during storage, maintaining storage stability even when pigment concentration is increased to reduce the frequency of ink refilling and thus running costs.
3Reliability
If low-viscosity cationically polymerizable compound is used to maintain discharge stability at high pigment concentration, then discharge stability is maintained, but viscosity control becomes more challenging
Solution Approach 1:
The patent employs excessive polyfunctionality in the cationic polymerizable compound (60-100 wt% polyfunctional monomers), which provides multiple polymerization sites per molecule. This partial or excessive action compensates for the low viscosity by creating a highly crosslinked polymer network upon curing, thereby achieving both discharge stability during printing and adequate viscosity control for proper ink handling.
Solution Approach 2:
The patent carefully controls the molecular weight and functional group density parameters of the cationic polymerizable compound to achieve the optimal viscosity range (≤12 mPa·s). By adjusting these parameters, the formulation maintains low viscosity for stable discharge while providing sufficient bulk for proper inkjet handling and deposition.
4Manufacturing precision
If high pigment concentration is used to improve image quality, then image quality is improved, but curability deteriorates
Solution Approach 1:
The patent formulates a composite ink system where the cationic polymerizable compound serves dual functions as both viscosity modifier and polymerization precursor. The specific composition ratio and chemical structure of this composite enable the formulation to maintain curability at high pigment concentrations by ensuring sufficient penetration of UV light and mobility of polymerization species through the pigment-laden medium.
Solution Approach 2:
The patent optimizes the functional monomer content parameter (60-100 wt% polyfunctional monomers) to enhance the polymerization reactivity and network formation efficiency. This parameter change ensures that even with high pigment concentration absorbing UV energy, the remaining light can initiate rapid and complete curing of the low-viscosity cationic polymerizable compound, maintaining both image quality and curability.
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 provides excellent discharge stability, storage stability, and curability at high pigment concentrations, resulting in high-quality images with low noise and low running costs, suitable for inkjet recording.
Implementation Method 1
an ink composition comprising (A) a pigment other than titanium oxide, (B) a cationically polymerizable compound, and (C) a photo-acid generator
Implementation Method 2
the discharging is carried out using an inkjet head that discharges an ink composition by means of deformation of a piezoelectric element
Data Source
AI summary
An ink composition is provided that includes (A) a pigment other than titanium oxide, (B) a cationically polymerizable compound, and (C) a photo-acid generator, the pigment (A) having a content of 3.5 to 20 wt %, the cationically polymerizable compound (B) containing only an oxirane compound and/or an oxetane compound, the oxirane compound and/or the oxetane compound containing a low-viscosity compound having a viscosity at 25°C of no greater than 12 mPa·s, and the low-viscosity compound having a total content of 65 to 100 wt % relative to the total weight of the cationically polymerizable compound (B). There is also provided an ink composition that includes (A') titanium oxide, (B) a cationically polymerizable compound, and (C) a photo-acid generator, the titanium oxide (A') having a content of 35 to 45 wt %, the cationically polymerizable compound (B) containing an oxirane compound, oxetane compound, or vinyl ether compound having a viscosity at 25°C of no greater than 12 mPa·s, and the oxirane compound, oxetane compound, and vinyl ether compound having a viscosity at 25°C of no greater than 12 mPa·s having a total content of 65 to 100 wt % relative to the total weight of the cationically polymerizable compound (B). There is also provided an inkjet recording method that includes (a1) a step of discharging the ink composition above onto a recording medium and (b1) a step of curing the ink composition by irradiating the discharged ink composition with actinic radiation.