Aqueous Ink Transfer in Digital Printing With Hydrophilic ITM Films
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Solution Overview
Problem
Existing digital printing processes face challenges in achieving efficient transfer and adhesion of aqueous ink images onto printing substrates using intermediate transfer members (ITMs), particularly due to hydrophobic surfaces and inadequate treatment formulations.
Innovation Solution
The use of a silicone-based release layer with specific hydrophilic properties and an aqueous treatment formulation containing quaternary ammonium salts, water-soluble polymers, and a carrier liquid, applied to form a thin, cohesive dried treatment film on the ITM, followed by ink deposition and transfer to the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional hydrophobic ITM surface is used, then the release properties are good, but the adhesion of aqueous ink is poor
Solution Approach 1:
The ITM surface is pre-treated with a hydrophilic treatment formulation containing quaternary ammonium salts and water-soluble polymers before ink deposition. This preliminary action modifies the surface properties to be hydrophilic, enabling better adhesion of aqueous ink while maintaining the underlying silicone-based release layer structure.
Solution Approach 2:
The surface energy parameters of the ITM are changed by applying a treatment formulation that reduces surface tension and increases hydrophilicity. The treatment creates a surface with specific contact angle properties (receding contact angle ≤60°, 10-second dynamic contact angle ≤108°) that are optimal for aqueous ink adhesion while preserving release functionality.
2Productivity
If the ITM surface is made hydrophilic to improve ink adhesion, then the ink transfer efficiency improves, but the release layer functionality may be compromised
Solution Approach 1:
The treatment formulation creates a localized hydrophilic surface layer on the ITM without altering the bulk properties of the silicone-based release layer. The hydrophilic treatment is confined to the surface region, providing localized ink adhesion enhancement while the underlying release layer maintains its original release properties.
Solution Approach 2:
The ITM structure becomes a composite system combining the silicone-based release layer with a hydrophilic treatment layer containing quaternary ammonium salts and water-soluble polymers. This composite structure integrates the release properties of silicone with the adhesion properties of the hydrophilic treatment, achieving both functions simultaneously.
3Reliability
If a thick treatment layer is applied to ensure complete coverage, then the adhesion improves, but the drying time and process complexity increase
Solution Approach 1:
Instead of applying a thick treatment layer, the formulation is designed to achieve effective coverage at thin application thickness. The quaternary ammonium salt and water-soluble polymer combination provides sufficient adhesion promotion even when applied as a thin layer, reducing drying time while maintaining complete surface coverage and ink adhesion.
Solution Approach 2:
The treatment formulation creates a thin surface layer that copies or mimics the ideal surface properties needed for ink adhesion. Rather than building up thick layers to achieve coverage, the formulation itself is designed to spread uniformly and form an adequate thin film that provides the necessary adhesion function.
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 enhances the transfer and adhesion of aqueous ink images, ensuring smooth, uniform deposition and efficient transfer onto printing substrates, with improved ink dot formation and reduced surface tension-driven beading.
Implementation Method 1
The aqueous treatment formulation has a static surface tension within a range of 20 and 40 dynes/cm at 25° C.
Implementation Method 2
subjecting the wet treatment layer to a drying process to form a dried treatment film, from the wet treatment layer, on the silicone-based release layer surface
Implementation Method 3
providing an intermediate transfer member (ITM) comprising a silicone-based release layer surface that is sufficiently hydrophilic to satisfy at least one of the following properties: (i) a receding contact angle of a drop of distilled water deposited on the silicone-based release layer surface is at most 60°
Data Source
AI summary
Embodiments of the invention relate to a method of indirect printing with an aqueous ink. Related apparatus, systems and treatment formulations are disclosed herein. Some embodiments relate to an aqueous treatment formulation for use with an intermediate transfer member of a printing system. In some embodiments, the system comprises a treatment station disposed downstream of the impression station and upstream of the image forming station for forming a uniform thin layer of a liquid treatment formulation onto a surface of an intermediate transfer member (ITM) at a lower run thereof.