Water-in-oil emulsion ink for high-density printing
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Solution Overview
Problem
Inkjet printing methods face challenges in achieving high printing density on plain paper without causing strike-through and bleeding, particularly with aqueous and oil inks, which result in low resolution and curl issues.
Innovation Solution
The use of a water-in-oil (W/O) emulsion ink system where the first ink contains a coloring material with an acidic group and the second ink contains a polyvalent metal salt, allowing the coloring material to aggregate and stay on the printing medium, preventing permeation and enhancing printing density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If oil inks are used, then high-speed printing and low curl are achieved, but printing density decreases and strike-through/bleeding occurs
Solution Approach 1:
The ink is segmented into distinct oil phase and water phase components. The coloring material is confined to the water phase droplets dispersed in the oil continuous phase, separating the functions of carrier (oil) and colorant (water phase with coloring material), enabling high-speed printing while maintaining density.
Solution Approach 2:
The invention uses composite emulsion ink material combining oil and water phases. The W/O emulsion structure integrates the advantages of both oil-based (high-speed printing, low curl) and water-based (high density, good adhesion) inks, achieving both high-speed printing capability and high printing density without strike-through.
2Manufacturing precision
If aqueous inks are used, then high printing density and resolution are achieved, but prints develop curls and conveyance becomes difficult
Solution Approach 1:
The invention inverts the conventional O/W emulsion structure to use W/O emulsion. Instead of water continuous phase with oil droplets, it uses oil continuous phase with water phase droplets containing coloring material. This inversion enables the ink to dry without curling while maintaining high density, as the oil continuous phase prevents paper curling.
Solution Approach 2:
The W/O emulsion composite material combines the curl-prevention property of oil-based inks with the high-density capability of water-based inks. The coloring material in water phase droplets provides high adhesion and density, while the oil continuous phase prevents print curling.
3Adaptability or versatility
If conventional emulsion ink is used, then intermediate properties between aqueous and oil inks are achieved, but printing density remains similar to oil inks
Solution Approach 1:
The invention applies local quality by concentrating the coloring material specifically in the water phase droplets rather than distributing it throughout the entire emulsion. This localized placement ensures that the coloring material benefits from the high adhesion and density properties of water-based systems while the oil continuous phase provides high-speed printing characteristics.
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
This approach significantly improves printing density while preventing strike-through and bleeding, even on plain paper, by effectively aggregating the coloring material on the surface, thus enhancing the quality and durability of printed images.
Implementation Method 1
the coloring material contained in the water phase of the first ink is caused to be aggregated and stayed on the printing medium
Implementation Method 2
a water-in-oil (W/O) emulsion ink comprising a polyvalent metal salt in a water phase
Data Source
AI summary
In an inkjet printing system using an emulsion ink, it is aimed that printing density is improved particularly for a normal paper. An inkjet printing method is provided, in which printing is performed by ejecting one of first and second inks onto a printing medium, and then successively ejecting the other ink so as to overlay it in the one ink, wherein the first ink is a water-in-oil (W/O) emulsion ink comprising the coloring material which is provided with an acidic group on a surface in the water phase, and the second ink is a water-in-oil (W/O) emulsion ink comprising a polyvalent metal salt in the water phase. Preferable acidic group is carboxylic group, sulfuric acid group and phosphoric group. Preferable polyvalent metal salt is a salt composed of metal ions such as Ca++, Cu++, Ni++, Mg++, Zn++, Ba++, Al+++, Fe+++ and Cr+++.