Liquid Ejecting Head Wiring Protection Against Ink Corrosion
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Solution Overview
Problem
Piezoelectric actuators in liquid ejecting heads, such as ink jet type recording heads, face issues with electrical connection reliability due to environmental factors like moisture, especially when using ink containing solvents, leading to corrosion and electrical malfunctions.
Innovation Solution
A liquid ejecting head with a piezoelectric element and gold or platinum wiring, covered by an insulating protective layer made of materials like chromium, nickel, or aluminum, which improves ink resistance and migration resistance, preventing corrosion and electrical malfunctions even in severe environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the piezoelectric actuator is covered with a protective substrate and protective film, then the piezoelectric actuator is protected from environmental damage, but the electrical connection reliability deteriorates due to fine wiring being exposed to severe conditions
Solution Approach 1:
The patent applies different protective measures to different regions: the piezoelectric actuator is covered with a protective substrate and protective film for environmental protection, while the wiring leading-out portions are specifically covered with an insulating protective layer to prevent corrosion and electrical malfunctions. This localized differentiation resolves the contradiction by providing targeted protection where needed.
Solution Approach 2:
The insulating protective layer acts as an intermediary between the wiring and the harsh environment (ink containing solvents). This intermediate layer prevents direct contact between the wiring and corrosive substances, thereby maintaining electrical connection reliability without compromising the overall protection of the piezoelectric actuator.
2Reliability
If the wiring layer is made of gold or platinum, then the electrical conductivity is improved, but the resistance to corrosion and ink penetration deteriorates
Solution Approach 1:
The wiring structure uses a composite material system consisting of a gold or platinum wiring layer for electrical conductivity combined with an insulating protective layer (made of materials such as silicon oxide, zirconium oxide, or aluminum oxide) for corrosion resistance. This composite structure resolves the contradiction by combining the advantages of both materials.
Solution Approach 2:
The insulating protective layer serves as an intermediary barrier between the gold or platinum wiring and the corrosive ink environment. This intermediate layer prevents direct interaction between the wiring material and corrosive substances, thereby maintaining both electrical conductivity and corrosion resistance.
3Reliability
If the insulating protective layer is made thicker, then the ink resistance and migration resistance are improved, but the adhesion to the underlayer may deteriorate
Solution Approach 1:
The patent applies different thickness characteristics to different regions of the insulating protective layer: the layer is made thicker in regions where ink resistance and migration resistance are critical (such as covering exposed portions of the underlayer), while maintaining appropriate thickness in other regions to ensure good adhesion. This localized thickness differentiation resolves the contradiction.
Solution Approach 2:
The insulating protective layer is formed using composite material structures (such as stacking multiple layers of different materials like silicon oxide, zirconium oxide, and aluminum oxide) to achieve both sufficient thickness for resistance and appropriate adhesion properties. The composite structure allows optimization of both parameters simultaneously.
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 enhances the reliability of the liquid ejecting head by preventing corrosion and electrical malfunctions, ensuring stable operation under severe conditions.
Implementation Method 1
a piezoelectric actuator provided on a surface side of the flow path forming substrate with a vibration plate interposed therebetween and having a first electrode, a piezoelectric layer, and a second electrode, and discharges ink droplets from the nozzle by generating pressure change in the pressure generation chamber by displacement of the piezoelectric actuator
Implementation Method 2
an insulating protective layer which covers at least an exposed portion on the underlayer of the leading-out wiring... ink resistance and migration resistance are improved
Data Source
AI summary
A liquid ejecting head includes a piezoelectric element which includes a piezoelectric layer, and a first electrode and a second electrode sandwiching the piezoelectric layer therebetween, a leading-out wiring provided on an upper portion of the piezoelectric element and including a wiring layer made of gold or platinum and an underlayer which are patterned, and an insulating protective film which covers at least an exposed portion on the underlayer of the leading-out wiring.