Inkjet Printing Head Ink Application Order for Beading Control
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Solution Overview
Problem
Printing apparatuses using ink containing a pigment and a less permeable printing medium experience marked beading, leading to degraded image quality due to the ink droplets' inability to spread and wet the surface effectively, resulting in nonuniform images and increased graininess, especially when printing high-tone images.
Innovation Solution
A printing apparatus with a printing head capable of ejecting two color inks with different contact angles, where the ink with a larger contact angle on the second ink's layer is applied to fewer pixel areas than the ink with a smaller contact angle on its own layer, controlling the ejection to reduce beading by ensuring the second ink is applied to more areas after the first ink, thus enhancing wettability and image uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If ink containing a pigment is fixed to the surface of a less permeable printing medium, then the ink remains in a liquid state for a longer time, but this causes marked beading and degraded image quality
Solution Approach 1:
The patent applies a first ink containing a surfactant before applying the second ink containing a pigment. The first ink is applied in advance to modify the surface properties of the printing medium, reducing surface tension and preventing beading of the subsequently applied second ink. This preliminary action ensures that the second ink spreads properly and maintains uniform distribution on the less permeable printing medium.
Solution Approach 2:
The first ink acts as an intermediary substance between the printing medium and the second ink. It modifies the surface characteristics of the printing medium by depositing surfactant, which then facilitates proper wetting and spreading of the second ink. This intermediary layer prevents direct adverse interaction between the second ink and the hydrophobic less permeable printing medium surface.
2Reliability
If the second ink is applied to a layer made of the first ink, then the wettability is improved, but the ink droplets do not spread effectively on less permeable printing medium
Solution Approach 1:
The patent changes the surface tension parameter of the printing medium by applying a first ink containing a surfactant. This surfactant deposition modifies the critical surface tension of the surface, enabling the second ink to wet and spread properly. The parameter change transforms the printing medium surface from hydrophobic to hydrophilic, ensuring uniform distribution of the second ink droplets.
3Adaptability or versatility
If multiple inks are ejected onto the same region, then color images can be formed, but beading occurs when inks are applied close to each other
Solution Approach 1:
The first ink containing a surfactant is applied in advance to prepare the surface for subsequent ink applications. This preliminary surfactant deposition ensures that when multiple inks are ejected onto the same region, they all benefit from the modified surface properties, preventing beading and ensuring uniform mixing and distribution of different ink colors.
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 reduces image degradation by minimizing beading and graininess, improving the overall quality of printed images by optimizing the application order of inks based on their contact angles, ensuring better spreading and wetting of ink droplets on the printing medium.
Implementation Method 1
the ink is kept in a liquid state on the printing medium for a longer time than the conventional case where ink is fixed to a printing medium by permeation of the ink
Implementation Method 2
the wettability of the second ink on a layer made of the first ink is higher than the wettability of the first ink on a layer made of the second ink
Data Source
AI summary
When the contact angle of a first color ink on a layer of a second color ink is larger than the contact angle of the second color ink on a layer of the first color ink, ejection of the first and the second color ink is controlled so that the number of pixel areas onto which the second color ink is applied after the first color ink is larger than the number of pixel areas onto which the first color ink is applied after the second color ink.