Starch-Based Coating for Aqueous Inkjet Transfer
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Solution Overview
Problem
Aqueous indirect inkjet printing faces challenges in achieving optimal wet image quality, image transfer, and print-head management due to competing requirements for ink spread and adhesion, with existing solutions often compromising image quality for efficient transfer.
Innovation Solution
An improved coating for the image receiving member, comprising a hydrophilic starch composition with a surfactant, applied to the blanket surface to enhance ink spread and cohesion, while minimizing adhesion to the blanket, ensuring complete ink transfer and maintaining print-head functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a low surface energy blanket material is used to facilitate ink transfer, then image transfer efficiency is improved, but ink spread and wet image quality deteriorate
Solution Approach 1:
The blanket surface is pre-treated with a hydrophilic coating composition containing starch and surfactant before ink application. This preliminary action modifies the surface properties to temporarily increase surface energy and hydrophilicity, enabling proper ink spread and wet image quality during the printing process, while the underlying low surface energy blanket material remains intact for subsequent ink transfer.
Solution Approach 2:
The surface energy and hydrophilicity parameters of the blanket are dynamically changed through coating application. The hydrophilic coating composition alters the surface characteristics during the printing process to improve ink spread, while the low surface energy blanket material restores its original properties after printing to facilitate ink transfer. This parameter change approach resolves the contradiction by having different surface properties at different process stages.
2Manufacturing precision
If the ink surface tension is reduced to improve spread, then ink distribution is improved, but adhesion to the blanket deteriorates
Solution Approach 1:
The hydrophilic coating composition acts as an intermediary layer between the ink and the low surface energy blanket. This intermediary coating provides a surface that promotes both ink spread and adhesion simultaneously, resolving the contradiction by mediating the interaction between ink and blanket without requiring extreme changes in ink surface tension.
3Manufacturing precision
If a high surface energy blanket is used to promote ink spread, then wet image quality is improved, but ink transfer to media deteriorates
Solution Approach 1:
The blanket surface is pre-coated with hydrophilic material before printing to achieve high surface energy for ink spread. After the printing process, the coating is removed or degraded, restoring the blanket's original low surface energy properties for efficient ink transfer. This temporal separation of surface energy requirements resolves the contradiction.
Solution Approach 2:
The blanket surface energy parameter is changed during the printing process by applying hydrophilic coating, then restored afterward. This dynamic parameter change allows the system to have high surface energy when needed for ink spread, and low surface energy when needed for ink transfer, eliminating the need to permanently compromise either property.
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 starch-based coating promotes high-quality ink spread, complete image transfer, and efficient cleaning of the print-head, maintaining image quality and transfer efficiency without compromising the print-head's operation, even at varying temperatures.
Implementation Method 1
The starch-based coating promotes high-quality ink spread, complete image transfer
Implementation Method 2
Spreading of aqueous ink is facilitated by materials having a high energy surface. In order to facilitate transfer of the ink image from the blanket to the media substrate, however, a blanket having a surface with a relatively low surface energy is preferred.
Implementation Method 3
The improved starch-based coating composition is applied to the surface of the blanket and at least partially dried before the aqueous ink is applied
Data Source
AI summary
An aqueous ink transfer process includes coating the surface of an image transfer member (ITM) with a coating composition to a first thickness, the coating composition including a hydrophilic composition and a surfactant, partially drying the coating composition to reduce its thickness and then applying aqueous ink onto the coating composition. The coating composition in the vicinity of the applied ink swells by absorbing water from the ink, and can further exhibit reduced adherence to the ITM. The ink is partially dried and then transferred onto a substrate.