Stochastic Pixel Mask for Digital Printing Ink Coalescence
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Solution Overview
Problem
Digital printing techniques face limitations in resolution and image quality due to ink wicking into porous substrates, especially in direct printing, and the use of coated substrates is costly and impractical for commercial applications, while indirect printing faces challenges with ink penetration and duplex printing.
Innovation Solution
A method and system for digital printing that applies a specific N×M pixel-image mask to convert non-binary multi-level digital images into ink images, using stochastic patterns and ink deposition processes to control the formation of pixel-clusters on a target surface, ensuring that neighboring clusters nearly touch without touching, and adjusting the lightness levels to optimize bridge-pixel combinations, thereby improving image quality and preventing ink coalescence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If direct inkjet printing is used on porous substrates, then printing process is simple and cost-effective, but ink wicking occurs causing poor resolution and image quality
Solution Approach 1:
An intermediate transfer member (ITM) is introduced between the inkjet print head and the final substrate. The ITM receives the inkjet image and transfers it to the substrate, preventing direct ink-substrate interaction that causes wicking. This intermediary allows ink to be deposited on a non-porous surface first, then transferred cleanly to the final substrate.
Solution Approach 2:
The printing process is divided into separate stages: ink deposition on the intermediate transfer member, drying on the ITM surface, and subsequent transfer to the final substrate. This segmentation allows each stage to be optimized independently - ink can be deposited without worrying about substrate porosity, then transferred in a controlled manner.
2Manufacturing precision
If coated substrates are used to prevent ink wicking, then image quality improves, but substrate cost increases and additional drying steps are required
Solution Approach 1:
The intermediate transfer member with its specific surface properties (such as hydrophobic treatment) acts as a mediator that prevents ink wicking without requiring the final substrate to be coated. The ITM surface is engineered to control ink behavior, eliminating the need for expensive coated substrates and additional drying steps.
Solution Approach 2:
The intermediate transfer member's surface properties enable self-drying of the ink deposit before transfer. The hydrophobic or specially treated surface allows ink to dry in place without external drying equipment, then the dried image is transferred to the substrate, eliminating additional costly drying steps.
3Extent of automation
If conventional half-toning methods are used, then binary images can be printed, but ink coalescence and graininess occur reducing print quality
Solution Approach 1:
Instead of uniform pixel distribution, the patent applies different spatial distributions to different regions or density levels. By varying the local arrangement and spacing of pixel clusters according to specific patterns (such as stochastic or blue-noise patterns), the method prevents regular coalescence patterns while maintaining overall gray-level accuracy, thereby improving print quality.
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 print quality by minimizing ink coalescence and graininess, maintaining uniformity in gray-level images and improving duplex printing capabilities without the need for costly substrate coatings, while maintaining the ink on the surface for better image fidelity.
Implementation Method 1
the respective chemical and/or physical properties of the ink and of the target surface it may interact with
Implementation Method 2
centroids of clusters of the array being spatially distributed according to a stochastic pattern
Data Source
AI summary
There is provided an ink-deposition device suitable for depositing ink on a target surface and a printing system comprising the same. In operation in a printing system, the ink-deposition device can convert digital images into ink images on the target surface using pixel-masks and methods as disclosed herein. Advantageously, the ink-deposition device, the printing system comprising it and the methods of using the same can reduce or prevent the occurrence of some undesired ink-formations typically governed by the respective physical and/or chemical properties of the surface and ink being used or mitigate their effect on print quality. Application of the pixel-image mask yields a binary image that exhibits pixel-clusters with stochastically distributed centroids.