Sacrificial Coating for Indirect Inkjet Printers
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Solution Overview
Problem
Indirect inkjet printers face challenges in achieving both good wet image quality and image transfer with aqueous inks, as high surface energy materials promote spreading but low surface energy materials cause 'beading', and existing solutions struggle to balance these requirements while maintaining water fastness.
Innovation Solution
A sacrificial coating composition comprising waxy starch, cross-linkers, hygroscopic materials, and surfactants is applied to the intermediate transfer member, providing a hydrophilic surface for ink spreading and improved transfer characteristics, along with enhanced water fastness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a high surface energy blanket material is used, then wet image quality is improved through better ink spreading and coalescing, but image transfer performance deteriorates due to increased ink attraction to the blanket
Solution Approach 1:
The invention divides the blanket surface into two distinct layers: a base layer made of low surface energy material (silicone, fluorosilicone, fluoropolymer, or hybrid) for good image transfer, and a sacrificial coating layer made of hydrophilic materials (starch, polyvinyl alcohol, gelatin, or carboxymethyl cellulose) for good wet image quality. This segmentation allows each layer to perform its specific function without compromise.
Solution Approach 2:
The invention changes the surface energy parameter of the blanket by applying a sacrificial coating that temporarily modifies the surface properties during printing. The coating provides high surface energy for ink spreading, then is removed after use, restoring the original low surface energy for image transfer. This dynamic parameter change resolves the contradiction between wet image quality and image transfer.
2Reliability
If a low surface energy blanket material is used, then image transfer is improved with minimal ink attraction, but wet image quality deteriorates due to ink beading and poor spreading
Solution Approach 1:
The invention divides the blanket surface into two distinct layers: a base layer made of low surface energy material (silicone, fluorosilicone, fluoropolymer, or hybrid) for good image transfer, and a sacrificial coating layer made of hydrophilic materials (starch, polyvinyl alcohol, gelatin, or carboxymethyl cellulose) for good wet image quality. This segmentation allows each layer to perform its specific function without compromise.
Solution Approach 2:
The invention applies the sacrificial coating layer beforehand on the blanket surface before printing operations. This preliminary action prepares the surface with high energy properties for optimal ink spreading and wet image quality, while the underlying low energy base layer remains ready to facilitate image transfer after the coating is removed.
3Manufacturing precision
If hydrophilic coating materials are used to improve ink spreading, then wet image quality is improved, but water fastness deteriorates due to increased ink solubility and smudging
Solution Approach 1:
The invention uses a sacrificial coating that is intentionally designed to be removed after serving its purpose. The hydrophilic coating improves wet image quality during printing, then is completely removed after the print cycle using water or steam. This discarding approach eliminates water fastness issues because the coating that could cause smudging is no longer present on the final printed product.
Solution Approach 2:
The invention extracts the problematic hydrophilic coating material from the final printed product by removing it after printing. The coating is applied to the blanket, serves its function during printing, then is extracted through water or steam removal processes. This extraction eliminates the source of water fastness problems while preserving the benefits during the printing process.
Data Source
AI summary
An embodiment of the present disclosure is directed to a wet sacrificial coating composition. The coating composition is made from ingredients including: a waxy starch; at least one cross-linker; at least one hygroscopic material; at least one surfactant; and a liquid carrier.