Sacrificial Coating for Ink Spreading and Transfer
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Solution Overview
Problem
Indirect printing processes face challenges in achieving optimal ink spreading and transfer due to conflicting requirements for high surface energy for wet ink spreading and low surface energy for image transfer, leading to inefficiencies and increased ink waste.
Innovation Solution
A sacrificial coating composition comprising polyvinyl alcohol, waxy starch, a hygroscopic agent, and surfactant, with a specific weight ratio and molecular weight range, is applied to the intermediate transfer member to enhance ink spreading and transfer efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a blanket having a high surface free energy is used, then ink spreading and coalescing is enhanced, but image transfer to the media substrate deteriorates due to strong attraction between ink and blanket
Solution Approach 1:
The patent applies a sacrificial coating to the blanket surface before ink deposition. This coating temporarily modifies the blanket surface properties to enable ink spreading and coalescing during the printing process, then is removed after transfer to restore the original low surface energy state for efficient image transfer.
Solution Approach 2:
The patent changes the surface energy parameter of the blanket dynamically by applying a sacrificial coating that increases surface free energy temporarily during ink deposition, then removes it afterward to restore low surface energy conditions for effective image transfer.
2Productivity
If a blanket having a low surface free energy is used, then image transfer to the media substrate is facilitated, but ink spreading and coalescing deteriorates causing grainy images and deletions
Solution Approach 1:
The sacrificial coating is applied in advance to the blanket surface to create temporary high surface energy conditions that promote ink spreading and coalescing, before the actual printing process occurs.
Solution Approach 2:
The sacrificial coating acts as an intermediary substance between the low surface energy blanket and the aqueous ink, enabling ink spreading by providing a temporary high surface energy interface, while still allowing image transfer to occur.
3Adaptability or versatility
If conventional lithographic systems are used for variable printing, then printing capability is maintained, but transfer efficiency deteriorates with significant ink waste requiring extensive cleaning
Solution Approach 1:
The sacrificial coating modifies the blanket surface parameters to optimize both variable data printing performance and ink transfer efficiency, reducing ink waste and eliminating the need for extensive cleaning between prints.
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 composition improves ink spreading and transfer efficiency, reducing ink waste and maintaining printer run-ability while providing improved image quality and mechanical properties.
Implementation Method 1
A sacrificial coating composition comprising polyvinyl alcohol, waxy starch, a hygroscopic agent, and surfactant
Implementation Method 2
Spreading of aqueous ink may be facilitated by materials having a high surface free energy
Implementation Method 3
A sacrificial coating composition comprising polyvinyl alcohol, waxy starch, a hygroscopic agent, and surfactant
Data Source
AI summary
Disclosed herein are sacrificial coating compositions comprising at least one polyvinyl alcohol; at least one waxy starch; at least one hygroscopic agent; at least one surfactant; and water, wherein the ratio by weight of the at least one waxy starch to the at least one polyvinyl alcohol is at least two to one. In certain embodiments, the at least one polyvinyl alcohol has a degree of hydrolysis of at least about 95%, such as at least about 98%, or at least about 99.3%. In certain embodiments, the viscosity of the at least one polyvinyl alcohol in a deionized water solution at 20° C. ranges from about 30 cps to about 80 cps, wherein the solution contains 4% by weight polyvinyl alcohol relative to the total weight of polyvinyl alcohol and deionized water in the solution. Also disclosed herein are methods of making a sacrificial coating composition.