Ink Jet Head Upper Protective Layer for Kogation Removal
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Solution Overview
Problem
Ink jet printing systems face challenges in reliably removing kogations from the heat application portion of ink jet heads, leading to unstable ink ejection and poor print quality, particularly due to the formation of oxide films that hinder electrochemical reactions, and require cumbersome cleaning procedures that cannot be performed during printing operations.
Innovation Solution
The use of an upper protective layer made of materials like Ir or Ru, which dissolve through electrochemical reactions without forming oxide films, allowing for the electrochemical removal of kogations during printing operations, using the heat application portion as one electrode and another electrode connected through the ink, with voltage polarity reversal to enhance the removal process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective layer of Ta is formed to protect the electrothermal transducer against physical and chemical influences, then the reliability and life of the head are improved, but oxide films form on the surface during heating which hinder electrochemical reactions for removing kogations
Solution Approach 1:
The patent applies this principle by using a sacrificial upper protective layer made of Ir or Ru that can be selectively dissolved during cleaning operations. This layer is intentionally designed to be consumable - it protects the underlying structure during normal operation but can be removed through electrochemical dissolution when kogation removal is needed, allowing the system to self-clean without requiring removal of the entire protective structure.
Solution Approach 2:
The patent changes the material parameter from Ta (which forms oxide films) to Ir or Ru (which do not form oxide films at operating temperatures). This parameter change in material selection fundamentally alters the chemical behavior during heating, preventing oxide film formation while maintaining protective functions and enabling subsequent electrochemical cleaning.
2Reliability
If conventional cleaning methods using specialized cleaning liquids are used, then kogations can be removed, but the cleaning procedure becomes cumbersome and cannot be performed during printing operations
Solution Approach 1:
The patent implements self-service cleaning by enabling the ink jet head to clean itself using its own operational components. The upper protective layer serves as an electrode that can be electrically connected to external electrodes, allowing electrochemical dissolution of kogations during normal printing operations without requiring external cleaning liquids or specialized procedures. The system uses its own structure to perform the cleaning function.
Solution Approach 2:
The upper protective layer made of Ir or Ru serves multiple functions: it protects the electrothermal transducer from physical and chemical influences during normal operation, and simultaneously serves as an electrode for electrochemical cleaning when needed. This multi-functionality eliminates the need for separate cleaning components or specialized cleaning liquids, integrating the cleaning capability into the existing structure.
3Strength
If the upper protective layer is made of Ta to provide strong protection, then resistance against impacts and chemical actions is improved, but the material dissolves slowly in electrochemical reactions hindering effective kogation removal
Solution Approach 1:
The patent applies this principle by selecting Ir or Ru for the upper protective layer - materials that are sufficiently durable to provide protection during normal operation but can be selectively dissolved through electrochemical reactions during cleaning. These materials serve as a sacrificial layer that can be removed when needed, unlike Ta which is too resistant to dissolve effectively.
Solution Approach 2:
The patent changes the material composition parameter from Ta to Ir or Ru, which fundamentally alters the electrochemical properties. Ir and Ru maintain adequate protective strength while being much more responsive to electrochemical dissolution, enabling effective kogation removal. This parameter change optimizes both protective function and cleanability.
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 method ensures uniform and reliable removal of kogations, stabilizing ink ejection characteristics and enabling high-quality printing without the need for specialized cleaning procedures, as the electrochemical reaction can occur with ink present, using the ink jet head during normal printing operations.
Implementation Method 1
an upper protective layer which is arranged over the protective layer and includes at least a heat application portion which can contact with an ink and is disposed over the heating portion so that the upper protective layer can serve as an electrode to be electrically connected to cause an electrochemical reaction with the ink
Implementation Method 2
The electrothermal transducer is constructed of a heating resistor and an electrode to supply electricity to the resistor... when the electrothermal transducers are selectively driven, they generate a thermal energy which rapidly heats the ink through an ink contact member
Implementation Method 3
generating a bubble in ink... A pressure of the expanding bubble ejects an ink droplet
Data Source
AI summary
In an ink jet head using a thermal energy for ejecting ink, this invention aims to reliably and uniformly remove kogations deposited on a heat application portion in contact with the ink. To realize this objective, the upper protective layer is arranged in an area including the heat application portion so that it can be electrically connected to serve as an electrode which causes an electrochemical reaction with the ink. The upper protective layer is formed of a material containing a metal which is dissolved by the electrochemical reaction and which does not form, on heating, an oxide film which hinders the dissolution. With this arrangement, a reliable electrochemical reaction can be produced to dissolve a surface layer of the upper protective layer, thereby removing kogations on the heat application portion reliably and uniformly.