Inkjet Printing with Upstream Wetting Correction for Nozzle Defects
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Solution Overview
Problem
Inkjet printing apparatuses using UV ink face issues with nozzle variations and defects leading to uneven density and color in printed images, particularly in high-density regions, which conventional correction methods fail to adequately address.
Innovation Solution
The apparatus employs a three-head system where a third inkjet head ejects a correction ink upstream to enhance the wetting spread range, allowing for effective correction of defective nozzles and overlapping regions, with determination criteria for when to apply this correction based on ink coverage and nozzle defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional density uniformity correction and nozzle-defect correction are performed, then individual variations among nozzles are suppressed, but defective nozzles still cause dot missing and insufficient dot size in high-density regions
Solution Approach 1:
The correction ink is ejected in advance into the correction region before the main inks are ejected. This preliminary action creates a wetting layer that ensures subsequent ink droplets from potentially defective nozzles will still achieve adequate spread and coverage, preventing dot missing and insufficient dot size even when nozzle ejection is unreliable
Solution Approach 2:
The correction ink acts as an intermediary substance between the printing medium and the main inks. By establishing this intermediate wetting layer, the correction ink mediates the interaction between defective ink droplets and the substrate, ensuring proper ink spread and dot formation despite nozzle variations and defects
2Manufacturing precision
If a third inkjet head is added for correction ink ejection, then dot size and ink coverage are improved, but device complexity increases
Solution Approach 1:
The printing system is segmented into functional groups: main inkjet heads for primary ink ejection and a separate correction inkjet head for wetting layer formation. This segmentation allows each head to be optimized for its specific function while working together to achieve overall printing improvement
Solution Approach 2:
The correction inkjet head uses the same ink type (UV ink) as the main inkjet heads, allowing it to serve multiple purposes: creating wetting layers for defect correction, contributing to overall ink coverage, and maintaining consistency in curing characteristics across all ink ejection points
3Manufacturing precision
If correction ink is ejected into high-density regions, then dot size is increased, but ink solidification may cause additional dot missing
Solution Approach 1:
The correction ink is ejected as a thin wetting layer before the main inks, creating a preparatory surface that promotes ink spread. This preliminary action occurs in a controlled manner that avoids excessive ink accumulation, thereby preventing solidification issues while still achieving adequate dot size
Solution Approach 2:
The ink ejection parameters for the correction head are optimized to eject smaller volumes at lower frequencies compared to main inkjet heads. This parameter adjustment ensures the correction ink forms a wetting layer without creating excessive ink pools that would be prone to solidification and dot missing
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 significantly improves print quality by ensuring adequate ink coverage and dot size, effectively suppressing defects caused by defective nozzles and head module overlaps.
Implementation Method 1
the first ink has a larger wetting spread range on the printing medium when the first ink is ejected onto the third ink on the printing medium than when the first ink is ejected directly onto the printing medium
Data Source
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AI summary
To suppress the occurrence of image defects caused by a defective nozzle and other factors in a printed image to be formed on a base material by an inkjet printing apparatus, a region to be corrected in the image is determined. When the region to be corrected is a single-color high-density region to be formed by ejecting a single-color ink, or when the region is a mixed-color high-density region to be formed using two or more color inks, and the amount of ink in the color from the defective nozzle has a high total area coverage percentage, printing data is corrected such that the color ink ejection to the region is performed after white ink (when the base material is white) or transparent ink (when the base material is not white) is ejected. Based on the corrected printing data, the printed image is formed on the base material, thereby suppressing the occurrence of image defects caused by the defective nozzle and other factors.