Liquid Ejecting Head Electrode Thickness Gradient
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Solution Overview
Problem
Piezoelectric-type liquid ejecting heads face issues with cracking due to sharp voltage changes at the boundary between overlapping and non-overlapping portions of the piezoelectric layer, caused by the constant thickness of the upper electrode, leading to flexural deformation and high operational frequency.
Innovation Solution
A liquid ejecting head design where the second electrode has a varying thickness, with a thinner portion near the end, reducing electric resistance and preventing sharp voltage changes, and incorporating a less conductive portion to inhibit crack formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the upper electrode layer has constant thickness, then the manufacturing process is simple, but sharp voltage changes occur at the boundary between overlapping and non-overlapping portions causing cracks
Solution Approach 1:
The upper electrode layer is designed with different thicknesses in different regions: a first thickness in the overlapping portion and a second thickness (greater than the first) in the non-overlapping portion. This local variation in thickness creates corresponding variations in electric resistance that gently change voltage at boundaries, preventing crack formation while maintaining manufacturing feasibility through controlled deposition processes.
2Strength
If the upper electrode layer extends to inhibit flexural deformation, then the piezoelectric layer is protected from cracking, but the overlapping portion becomes distorted at high frequencies
Solution Approach 1:
The invention changes the thickness parameter of the upper electrode layer to control electric resistance distribution. By making the non-overlapping portion thicker, the electric resistance increases in this region, which gently changes voltage at the boundary and reduces operational distortion frequency, thereby stabilizing the overlapping portion during high-frequency operation.
3Manufacturing precision
If the boundary between overlapping and non-overlapping portions is sharp, then the electrode structure is well-defined, but voltage changes sharply causing crack formation
Solution Approach 1:
Rather than using a sharp boundary, the invention implements a gradual transition in electrode thickness from the overlapping to the non-overlapping portion. This creates a gradient in electric resistance that gently changes voltage at the boundary, maintaining well-defined electrode regions while preventing crack formation through controlled voltage distribution.
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 design gently changes voltage at the boundary, preventing cracking and enhancing the structural integrity of the piezoelectric layer, thereby improving the reliability of the liquid ejecting head.
Implementation Method 1
a piezoelectric layer; wherein the diaphragm, the first electrode, the piezoelectric layer, and the second electrode are comprised in this order
Implementation Method 2
the thickness of the first portion at the second position is less than the thickness of the first portion at the first position
Data Source
AI summary
A liquid ejecting head includes a diaphragm, a first electrode, a piezoelectric layer, and a second electrode in this order in a first direction, and ejects liquid. The second electrode includes a first portion that is next to the piezoelectric layer in the first direction and is electrically conductive. A length in the first direction is defined as a thickness. One position in a second direction intersecting with the first direction is defined as a first position. Another one position is defined as a second position that is closer to an end of the second electrode in the second direction than the first position is. Given the definition, the thickness of the first portion at the second position is less than the thickness of the first portion at the first position.