UV Inkjet Printing Pass Control for Stronger Ink Adhesion
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Solution Overview
Problem
Existing methods for applying UV curable ink on image receiving media face challenges with ink adhesion, particularly with certain inks on PVC-free media, as the ink layer close to the medium may not fully cure in a single step.
Innovation Solution
A method that includes adjusting the print mode to enhance adhesion by lowering the carriage speed in the main scanning direction, extending the pass time, and increasing the UV dose per unit area, allowing for longer interaction time between ink and medium, and curing the ink in the same pass or subsequent passes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the carriage speed is maintained at the first speed for efficient printing, then productivity is improved, but ink adhesion deteriorates because the ink layer does not have sufficient time to interact with the medium before curing
Solution Approach 1:
The carriage speed is dynamically adjusted based on the selected print mode. In enhanced adhesion mode, the speed is reduced from the first speed to a second speed during the pass, allowing sufficient interaction time between ink and medium. The system transitions between different speed states depending on operational requirements, making the speed parameter dynamic rather than fixed.
Solution Approach 2:
The invention changes the speed parameter from a constant first speed to a variable speed that can be set to a second speed (lower than the first) when enhanced adhesion is required. This parameter change allows the system to optimize between productivity and adhesion by selecting appropriate speed values based on the print mode.
2Reliability
If the carriage speed is lowered to enhance adhesion, then ink adhesion is improved, but productivity deteriorates due to extended printing time
Solution Approach 1:
The system dynamically adjusts carriage speed based on the print mode selection. When enhanced adhesion mode is selected, the speed is reduced to allow proper ink-medium interaction. When standard mode is selected, the higher first speed is used to maintain productivity. This dynamic adaptation allows the system to optimize for adhesion only when necessary.
Solution Approach 2:
The invention applies periodic variation in carriage speed during the printing process. The speed is reduced during passes where enhanced adhesion is needed and restored to normal speed during other passes, creating a periodic pattern of speed adjustment that balances adhesion requirements with overall productivity.
3Productivity
If a single-step curing process is used, then productivity is improved, but curing completeness deteriorates for thick ink layers
Solution Approach 1:
The invention applies preliminary action by extending the interaction time between ink and medium before curing occurs. By reducing the carriage speed during the printing pass, the system allows sufficient time for the ink layer to be properly deposited and interact with the medium, creating optimal conditions for subsequent curing whether in one step or multiple steps.
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
Improves ink adhesion by increasing the interaction time between ink and medium and enhancing the UV dose, ensuring complete curing and preventing banding artifacts.
Implementation Method 1
the ink is hardened by irradiating the ink with a suitable source of radiation, preferably UV radiation
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3
AI summary
The invention relates to a method of controlling a digital inkjet printer 3 for printing images on an image receiving medium 2 up to a maximum medium width. The digital printer 3 is arranged to operate in a selected first print mode which is characterized by a first speed in a main scanning direction X for at least one carriage 5,12. A digital image is received and a print setting that the digital image is planned to be printed in an enhanced adhesion print mode is received. A time period needed for a pass in the main scanning direction X is extended c1) by lowering a speed in the main scanning direction X from the first speed to a second speed, and c2) by enlarging the pass width up to a maximum medium width in the main scanning direction X and/or by temporarily stopping the at least one carriage 5,12 at an end of the pass. Marking material is ejected during the pass on the image receiving medium 2 by means of a print head 4a,4b,4c,4d,4e at the second speed within the extended time period, and Is cured by means of a UV curing device 11 at the second speed within the extended time period. The invention further relates to a digital inkjet printer configured to perform the above mentioned method.