Inkjet Printing Dot Connectivity Control for Rub Fastness
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Solution Overview
Problem
Ink jet printing methods using polymer emulsions and water-soluble organic solvents often result in images with low rub fastness due to inadequate film formation, particularly when inks have a low dynamic surface tension, leading to increased graininess and image separation from the printing medium.
Innovation Solution
An image processing apparatus that generates printing data for a printing head to eject inks with specific dynamic surface tensions, using mask patterns with varying print permitting pixel densities to control dot connectivity, ensuring that inks with low dynamic surface tension form images with high dot connectivity and those with high dynamic surface tension form images with low dot connectivity, thereby enhancing rub fastness and reducing graininess.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If inks with low dynamic surface tension are used, then the ink spreads well on the printing medium, but the rub fastness of the printed image decreases
Solution Approach 1:
The patent applies parameter changes by adjusting the dynamic surface tension of inks to different ranges based on the printing medium's absorbency. For less absorbent printing media, inks with lower dynamic surface tension (7-12 mN/m) are used to achieve good spreadability, while for absorbent printing media, inks with higher dynamic surface tension (13-18 mN/m) are used to maintain rub fastness. This parameter optimization resolves the contradiction between spreadability and rub fastness.
Solution Approach 2:
The patent applies local quality by selecting different ink formulations with specific dynamic surface tension ranges tailored to specific printing medium properties. Instead of using a single ink formulation for all media, the patent customizes ink characteristics to match the local requirements of different printing media types (absorbent vs. less absorbent), thereby achieving both good spreadability and rub fastness for each specific application.
2Stability of the object's composition
If inks with low dynamic surface tension are used, then the ink wets the printing medium effectively, but the image exhibits increased graininess
Solution Approach 1:
The patent resolves the contradiction between wetting uniformity and image graininess by optimizing the dynamic surface tension parameter within a specific range (7-12 mN/m for less absorbent media). This optimized range ensures sufficient wetting for uniform ink distribution while preventing excessive spread that would cause graininess, thereby achieving both good wetting uniformity and fine image quality.
3Reliability
If inks with high dynamic surface tension are used, then the image maintains good rub fastness, but the ink spreadability and wetting performance decrease
Solution Approach 1:
The patent applies parameter changes by using higher dynamic surface tension inks (13-18 mN/m) specifically for absorbent printing media where good rub fastness is the priority, while accepting reduced spreadability. Conversely, for less absorbent media, lower dynamic surface tension inks are used to maintain spreadability. This conditional parameter selection resolves the contradiction by matching ink properties to media characteristics.
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 approach effectively increases the rub fastness of printed images while minimizing graininess, ensuring the image remains intact upon rubbing and maintaining image quality.
Implementation Method 1
a printing head ejects ink through a plurality of ejection openings arranged therein while scanning the printing medium
Implementation Method 2
the ink dropped on the printing medium is heated so that the polymer emulsion coalesces into a film on the surface of the printing medium, thereby fixing the image
Implementation Method 3
the polymer emulsion coalesces into a film
Implementation Method 4
The solvent 54 contains a water-soluble organic solvent that functions as a film forming agent to reduce the temperature at which the polymer emulsion 53 starts coalescing into a film
Implementation Method 5
an ink having a relatively low dynamic surface tension is more likely to spread over the surface of the printing medium and wet it than inks having higher dynamic surface tensions
Implementation Method 6
The solvent 54 in the ink droplet 51 is more rapidly evaporated
Data Source
AI summary
When an image is printed with inks each containing a polymer emulsion and a film forming agent, the ejection of the inks is controlled so that the ink having a relatively low dynamic surface tension forms dots having a higher dot connectivity than the dots formed with the ink having a relatively high dynamic surface tension.