Piezoelectric Liquid Droplet Ejecting Head Stress Balancing
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Solution Overview
Problem
Liquid droplet ejecting heads with piezoelectric elements face durability issues due to unbalanced stress caused by the upper electrode structure, leading to potential cracking, especially at the free end of the electrode.
Innovation Solution
A liquid droplet ejecting head design featuring a pressure chamber substrate with oscillating plates covered by conductive layers and a piezoelectric layer, where extending portions between adjacent conductive layers help balance stiffness and distribute stress evenly, reducing the likelihood of cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the upper electrode extends to the outside of the pressure chamber or piezoelectric body, then the piezoelectric layer is protected from external factors such as humidity, but unbalanced stress is caused at the free end of the electrode leading to cracking
Solution Approach 1:
The patent applies asymmetry by making the upper electrode extend beyond the active area on only one side (one-sided extension) rather than symmetrically on both sides. This asymmetric configuration balances the stress distribution within the piezoelectric layer while still providing protection from external factors, thereby preventing cracking at the free end.
Solution Approach 2:
The patent applies local quality by extending the upper electrode selectively in specific regions (beyond the active area on one side) rather than uniformly across the entire structure. This localized extension provides targeted protection where needed while maintaining stress balance in other areas, preventing cracking in critical regions.
2Strength
If the upper electrode is confined within the active area, then stress balance is maintained, but protection from external factors such as humidity is reduced
Solution Approach 1:
The patent resolves this contradiction by using asymmetric extension of the upper electrode beyond the active area on one side only. This provides both stress balance (by avoiding symmetric extension on both sides) and enhanced protection from external factors (by extending beyond the active area boundary).
Solution Approach 2:
The patent extends the upper electrode in the planar dimension beyond the active area boundary, adding protective coverage in a different spatial dimension while maintaining stress balance through controlled extension geometry rather than vertical thickening.
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 enhances the durability of liquid droplet ejecting heads by balancing stress distribution and reducing the risk of cracking, thereby improving the longevity and reliability of the piezoelectric elements.
Implementation Method 1
The liquid droplet ejecting heads change the pressure within a pressure chamber formed below an oscillating plate by allowing the piezoelectric element to change the shape of the oscillating plate in response to driving signals
Data Source
AI summary
A liquid droplet ejecting head including a pressure chamber substrate that is provided with a pressure chamber communicating with a nozzle orifice, an oscillating plate formed over the pressure chamber at a first area surface; a plurality of first conductive layers formed over the oscillating plate which completely overlap and extend beyond the first area surface; a piezoelectric layer formed over the first conductive layers so as to overlap at least over the first area surface; and a second conductive layer, which is continuously formed so as to cover the piezoelectric layer and completely overlap and extend beyond the first area surface at extending portions, which extend in at least a part of an area between the first conductive layers adjacent to each other.