Liquid Ejection Head Substrate Structure for Electrochemical Kogation Removal
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Solution Overview
Problem
Existing thermal ink jet printing apparatuses face issues with kogation accumulation on the heat generating portions of the liquid ejection head substrate, leading to reduced thermal conductivity and unstable ink ejection due to the adherence of impurities, which complicates removal and affects design freedom.
Innovation Solution
A liquid ejection head substrate design featuring a first and second protection layer configuration, where the second protection layer includes a heating element side electrode portion and a counter electrode portion, allowing for electrochemical removal of kogation through an electrochemical reaction, while minimizing conductive residue generation and reducing manufacturing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single protection layer is used covering the heat generating portion, then the structure is simple, but kogation removal becomes difficult and thermal conductivity decreases
Solution Approach 1:
The protection layer is divided into two distinct layers: a first protection layer covering the heat generating portion and a second protection layer covering the first protection layer. This segmentation allows each layer to serve specific functions - the first layer protects the heat generating portion while the second layer enables electrochemical kogation removal, resolving the contradiction between structural simplicity and effective kogation removal capability.
Solution Approach 2:
The first protection layer acts as an intermediary between the heat generating portion and the second protection layer. It provides thermal insulation and electrical isolation, enabling the electrochemical reaction in the second layer to effectively remove kogation without directly exposing the heat generating portion to the electrochemical environment, thus facilitating reliable kogation removal while maintaining structural organization.
2Reliability
If the second protection layer is made conductive to enable electrochemical reaction, then kogation removal is effective, but electrical connection to heating element may occur causing instability
Solution Approach 1:
The first protection layer serves as an intermediary barrier between the heat generating portion and the second protection layer's electrochemical reaction zone. It provides electrical insulation that prevents direct electrical connection between the heating element and the counter electrode portion, while still allowing the electrochemical reaction to proceed effectively for kogation removal, thus ensuring ink ejection stability.
Solution Approach 2:
The second protection layer is designed with different functional zones: the heating element side electrode portion for electrochemical kogation removal and the counter electrode portion for completing the electrical circuit. The first protection layer provides localized electrical insulation specifically at the heating element interface, allowing conductive functionality where needed while preventing harmful electrical connections elsewhere.
3Reliability
If multiple protection layers are added for effective kogation removal, then thermal conductivity is maintained, but manufacturing complexity increases
Solution Approach 1:
The protection system is segmented into two layers with distinct functions: the first protection layer maintains thermal conductivity by covering only the heat generating portion with thermally conductive material, while the second protection layer enables electrochemical kogation removal. This segmentation allows each layer to be optimized for its specific function, maintaining thermal conductivity while enabling effective kogation removal without excessive manufacturing complexity.
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 design enables reliable removal of kogation, maintains thermal conductivity, and enhances design flexibility by preventing electrical connections between the heating element and counter electrode portions, thus stabilizing ink ejection and reducing manufacturing costs.
Implementation Method 1
a resistance heating element formed on a surface of the insulation layer on an opposite side of the first wiring layer and configured to generate thermal energy for ejecting a liquid by the electric power supplied from the first wiring layer
Implementation Method 2
a second protection layer formed to overlap the first protection layer. The second protection layer includes a heating element side electrode portion configured to overlap a portion of the first protection layer covering the resistance heating element, and a counter electrode portion located away from the heating element side electrode portion and configured to overlap a portion of the first protection layer covering the second wiring layer
Data Source
AI summary
A liquid ejection head substrate includes a first wiring layer, an insulation layer covering the first wiring layer, a resistance heating element formed on a surface of the insulation layer on an opposite side of the first wiring layer, a second wiring layer formed at a different portion from the resistance heating element on the surface of the first wiring layer, a first protection layer having an insulating property and covering the resistance heating element and the second wiring layer, and a second protection layer formed to overlap the first protection layer. The second protection layer includes a heating element side electrode portion overlapping a portion of the first protection layer covering the resistance heating element, and a counter electrode portion located away from the heating element side electrode portion and overlapping a portion of the first protection layer covering the second wiring layer.