Piezoelectric Head Insulating Layer Layout Against Hydrolysis
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Solution Overview
Problem
Existing liquid ejecting heads, such as ink jet recording heads, face issues with damage to piezoelectric layers due to short circuits and hydrolysis, which are not adequately addressed by existing adhesive layers that may leave air bubbles and insufficient insulation.
Innovation Solution
A novel configuration where the piezoelectric element includes a first electrode, a piezoelectric layer, a second electrode, a conductive layer, and an insulating layer, with specific stacking orders in different areas to enhance insulation and protection, particularly using an insulating layer to cover exposed portions of the piezoelectric layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an adhesive layer is used to cover the exposed portion of the piezoelectric layer, then protection against short circuit and hydrolysis is improved, but air bubbles may remain and insulation may be insufficient
Solution Approach 1:
The patent extracts the adhesive layer from the protection mechanism and replaces it with an insulating layer formed by a different method (such as sputtering or CVD). This eliminates the problem of air bubble entrapment while maintaining electrical insulation and moisture protection functions.
Solution Approach 2:
The patent introduces an insulating layer as an intermediary protective barrier between the piezoelectric layer and the environment. This layer serves as a mediator that provides both electrical insulation and moisture protection without the manufacturing defects associated with adhesive layers.
2Ease of manufacture
If the piezoelectric layer is exposed between wiring lines, then wiring connectivity is simplified, but the piezoelectric layer is vulnerable to damage from migration and moisture
Solution Approach 1:
The patent applies local quality by providing the insulating layer specifically at the exposed portions of the piezoelectric layer where wiring lines are present. This localized protection ensures that only the vulnerable exposed areas are covered, maintaining wiring connectivity while protecting against harmful factors.
Solution Approach 2:
The insulating layer acts as an intermediary barrier between the piezoelectric layer and the wiring lines/environment. It prevents direct contact that would allow migration and moisture ingress while maintaining the electrical connectivity function of the wiring lines.
3Power
If the second electrode extends to the end of the active portion, then electrical connection is optimized, but the piezoelectric layer becomes vulnerable to fire damage and short circuit
Solution Approach 1:
The patent segments the active portion into two functional zones: one where the second electrode is present for electrical connection, and another where the insulating layer is present for protection. This segmentation allows both electrical efficiency and reliability to be optimized in their respective zones.
Solution Approach 2:
The patent applies local quality by having the insulating layer extend to or beyond the end of the active portion, creating a protected zone at the edge. This localized protection prevents fire damage and short circuit at the vulnerable end regions while maintaining electrical connection efficiency in the main active area.
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 configuration effectively reduces damage from short circuits and hydrolysis, ensuring reliable operation of the piezoelectric elements by improving insulation and moisture barrier properties.
Implementation Method 1
a piezoelectric element that includes a first electrode, a piezoelectric layer, and a second electrode, a vibration plate that is vibrated when the piezoelectric element is driven
Data Source
AI summary
The vibration plate, the first electrode, the piezoelectric layer, and the second electrode are stacked in this order from the pressure chamber plate side in an active area facing the pressure chamber. An area located outwardly from the active area in a longitudinal direction of the pressure chamber includes a first area in which the piezoelectric layer, the second electrode, the insulating layer, and the first conductive layer are stacked in this order, and a second area in which the piezoelectric layer and the insulating layer are stacked in this order without the second electrode and the first conductive layer.