Liquid Ejection Head Substrate Dual Metal Protection Layers
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Solution Overview
Problem
The existing liquid ejection heads face challenges with the protection of energy generating elements, particularly when using strong alkaline inks, as silicon components can dissolve, and the protection performance of insulating layers degrades over time, leading to potential ink leakage.
Innovation Solution
A substrate with a first metal protection layer covering the insulating layer and a second metal protection layer covering the inner surface of the supply port, using materials like Au, Ni, or Pt to prevent silicon dissolution and ensure reliable operation even with alkaline inks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protection layer is provided on the inner wall of the supply port to prevent silicon dissolution, then the protection performance against alkaline liquid improves, but the protection performance gradually decreases depending on the type and use state of ink
Solution Approach 1:
The invention uses a composite protection structure consisting of an insulating layer (silicon oxide or silicon nitride) and a metal protection layer (Au, Ni, or Pt). This composite structure combines the electrical insulation properties of the insulating layer with the chemical resistance of the metal layer, providing both immediate protection against alkaline liquid and long-term durability that doesn't degrade with different ink types or usage conditions.
Solution Approach 2:
The metal protection layer acts as a sacrificial barrier that prevents direct contact between the alkaline liquid and the silicon base material. By using a thin layer of metal that is resistant to alkaline dissolution, the invention creates a disposable-like protective barrier that maintains its protective function throughout the intended lifespan of the liquid ejection head, preventing degradation over time.
2Reliability
If only an insulating layer is used to protect the energy generating element, then electrical insulation is provided, but ink can leak to line from gaps between the protection layer and insulating layer
Solution Approach 1:
The invention combines two different materials with complementary properties: the insulating layer provides electrical insulation, while the metal protection layer provides chemical resistance and seals potential gaps. This composite structure eliminates the vulnerability of using either material alone, preventing both electrical breakdown and ink leakage through the same protective system.
Solution Approach 2:
The protection system is divided into two distinct functional layers: the insulating layer handles electrical isolation requirements, while the metal protection layer handles chemical resistance and sealing requirements. This segmentation of functions allows each layer to be optimized for its specific purpose, with the metal layer filling gaps and sealing interfaces where the insulating layer alone would be insufficient.
Data Source
AI summary
When an insulating layer is provided in order to protect an energy generating element, there arises a possibility that the layer dissolves in a contacting liquid. Therefore, in order to eject liquid, a first protection layer containing metal is provided on the insulating layer facing a substrate for a liquid-ejection head and a second protection layer containing metal is provided on the surface of a liquid supply port to which a base containing silicon is exposed.