Electrowetting Inkjet Printhead for Coated Media Wetting
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Solution Overview
Problem
Inkjet printing systems face image quality issues due to interactions between media and ink, particularly on coated surfaces where ink does not wet well, leading to poor drop spread and line spread performance, and inter-color bleed caused by capillary pressure, resulting in overlay graininess.
Innovation Solution
A color inkjet printer is configured with a printhead, media transport, a platen of high dielectric constant material, and electrodes that emit an electric field to improve ink wetting on various media substrates, using an interdigitated electrode configuration and a closed-loop system to adjust voltage levels based on image quality parameters measured by an optical sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ink is ejected onto coated media, then the media surface is smooth and durable, but ink does not wet well resulting in poor drop spread and line spread performance
Solution Approach 1:
The patent applies an electric field to change the surface energy parameters of the coated media, temporarily modifying its wettability properties. This allows ink to spread properly on coated surfaces without compromising the media's durability, resolving the contradiction between media durability and ink spread performance.
Solution Approach 2:
The electric field acts as an intermediary mechanism between the ink and coated media surface. It mediates the interaction by temporarily reducing the surface energy of the coated media, enabling better ink wetting and spread while maintaining the media's inherent durability.
2Adaptability or versatility
If ink drops are ejected onto previously ejected ink drops of different colors, then color coverage is achieved, but inter-color bleed occurs due to capillary pressure
Solution Approach 1:
The patent changes the physical parameters of the ink drops by applying an electric field, which increases their stability and reduces capillary pressure. This prevents inter-color bleed while maintaining proper color coverage, resolving the contradiction between color coverage and color separation.
Solution Approach 2:
The patent converts the harmful capillary pressure that causes inter-color bleed into a beneficial effect. By applying an electric field, the capillary pressure is controlled and directed, actually improving ink stability and preventing unwanted bleed while maintaining color coverage.
3Manufacturing precision
If ink is ejected onto uncoated media, then ink wets the media well resulting in robust drop spread, but the media lacks durability and finish
Solution Approach 1:
The patent dynamically changes the surface energy parameters of uncoated media through electric field application. This allows the media to exhibit both the wetting properties of uncoated surfaces and the durability characteristics of coated surfaces, resolving the contradiction between drop spread performance and media durability.
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 solution effectively reduces overlay graininess by enhancing ink wetting and stability on different media types, ensuring optimal ink spread and minimizing inter-color bleed, thereby improving overall image quality.
Implementation Method 1
at least one electrode, and at least one electrical voltage source operatively connected to the at least one electrode to emit an electric field into a gap between the at least one printhead and the media transport
Implementation Method 2
The surface energies of inks and media drive many of these interactions. On uncoated media, ink wets the media well
Data Source
AI summary
A color inkjet printer includes an electrode that emits an electric field into a gap between a printhead and a media transport that carries media past the printhead. Image data generated by an optical sensor after an ink image is printed on the media is analyzed to measure at least one image quality metric. When the measured image quality metric is outside of a tolerance range, the voltage of a voltage source electrically connected to the electrode is adjusted to improve the wetting of the media type with the ink ejected by the printhead.