Aqueous Ink Dispersion with Gel Particles for Film Hardness
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Solution Overview
Problem
Existing aqueous photocurable compositions for ink jet image forming methods suffer from insufficient hardness and surface conditions of cured films, along with poor storage stability and difficulty in preparing aqueous dispersions due to components that are not easily dissolved or dispersed in water.
Innovation Solution
An aqueous dispersion comprising a resin with polymerizable groups, gel particles with a three-dimensional cross-linked structure containing urethane or urea bonds and a photopolymerization initiator, and water, where the gel particles have a hydrophilic group and contain a polymerizable monomer or sensitizer, is developed. This dispersion is manufactured through an emulsification step involving a photopolymerization initiator, isocyanate compounds, and polymerizable monomers, and applied onto a recording medium followed by active energy ray irradiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional aqueous photocurable compositions are used, then the composition can be applied to ink jet image forming, but the hardness and surface conditions of the cured film are insufficient
Solution Approach 1:
The invention uses a composite resin system combining (meth)acrylic acid-modified polyester resin and polyurethane resin, where the polyester resin provides hardness and the polyurethane resin improves surface conditions and adhesiveness. This composite approach allows both hardness and surface quality to be achieved simultaneously without compromise.
2Strength
If components with high light sensitivity are used to improve curing, then the hardness increases, but the storage stability deteriorates
Solution Approach 1:
The invention carefully controls the concentration of the photopolymerization initiator within 0.01-5 wt% and adjusts the functional group ratios (acrylic functional groups 0.1-5 mol%, carboxyl groups 0.1-5 mol%) to achieve optimal balance between light sensitivity for hardness and stability during storage. This parameter optimization prevents premature curing while ensuring adequate curing performance.
3Strength
If resin components are used that provide good film properties, then the hardness improves, but the ease of manufacture decreases due to difficulty in dissolving or dispersing in water
Solution Approach 1:
The invention introduces hydrophilic groups (carboxyl groups) at specific locations on the resin molecules to enable water dispersibility. The polyester resin contains carboxyl groups that provide local hydrophilicity, allowing the otherwise hydrophobic resin to form stable aqueous dispersions without requiring complex manufacturing processes.
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 enables the formation of films with enhanced hardness and surface conditions, improved storage stability, and excellent adhesiveness to substrates, while allowing for easy redispersibility and jetting properties, overcoming the limitations of previous compositions.
Implementation Method 1
an ink jet ink is known which contains at least one irradiation curable-type monomer, at least one inert thermoplastic resin, at least one radical photoinitiator, and at least one colorant
Data Source
AI summary
Provided is an aqueous dispersion including: a resin having a polymerizable resin; a gel particle which has a polymerizable group, has a three-dimensional cross-linked structure containing at least one kind of bond selected from a urethane bond and a urea bond, and contains a photopolymerization initiator in the interior of the gel particle; and water, in which a total amount of a solid content of the gel particle with respect to a total amount of the resin having a polymerizable group is 0.1% by mass to 100% by mass. Also provided are a method for manufacturing the aqueous dispersion and an image forming method using the aqueous dispersion.