Liquid-jet Head Lower Electrode Thickness Variation
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Solution Overview
Problem
Existing liquid-jet heads face challenges in achieving high-density arrangement of piezoelectric elements due to complex manufacturing processes and dielectric breakdown issues caused by electric field concentration at the lead-out ends of piezoelectric layers and electrodes.
Innovation Solution
A liquid-jet head design featuring a lower electrode with thin-thickness portions between adjacent piezoelectric elements, and notch portions to reduce electric field strength, along with uniform electrode widths and film quality to enhance durability and uniform ejection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a uniform piezoelectric material layer is formed on the entire surface of the vibration plate and cut into shapes corresponding to pressure generating chambers, then piezoelectric elements can be formed independently for each chamber, but electric field concentration occurs at end portions of the piezoelectric layers and upper electrodes, causing dielectric breakdown
Solution Approach 1:
The lower electrode is designed with varying thickness: a first thickness in regions corresponding to piezoelectric elements and a second thickness (greater than the first) in regions between adjacent piezoelectric elements. This local variation in electrode thickness creates corresponding variations in electric field distribution, concentrating the electric field where needed for actuation while reducing it in regions prone to dielectric breakdown, thereby resolving the contradiction between manufacturing precision and reliability
Solution Approach 2:
The invention changes the physical parameter of the lower electrode (thickness) to control electric field distribution. By adjusting the thickness parameter spatially across the electrode structure, the electric field strength is optimized locally - stronger under piezoelectric elements for effective actuation, and weaker in between to prevent breakdown, thus solving the reliability issue while maintaining manufacturing precision
2Reliability
If narrow-width portions are formed in the lower electrode to prevent dielectric breakdown, then dielectric breakdown is prevented, but pattern formation becomes complicated and alignment with piezoelectric layers and upper electrodes is difficult
Solution Approach 1:
Instead of creating narrow-width portions through complex patterning, the invention uses local variation in electrode thickness achieved through a simpler deposition or formation process. The lower electrode naturally forms different thickness regions that serve the same function as narrow-width portions but without requiring complex alignment and patterning steps, thus reducing device complexity while maintaining reliability
Solution Approach 2:
The invention replaces the mechanical patterning approach (cutting or etching narrow portions) with a field-based approach where electric field distribution is controlled through thickness variation. This substitution eliminates the need for precise mechanical alignment and complex pattern formation, simplifying the manufacturing process while achieving the same dielectric breakdown prevention effect
3Ease of manufacture
If flexural vibration mode piezoelectric actuators are used, then the manufacturing process is simple, but a certain area is required making high-density arrangement difficult
Solution Approach 1:
The invention changes the operational mode parameter of the piezoelectric elements from flexural vibration to longitudinal vibration. This parameter change allows the piezoelectric elements to be driven in the thickness direction, enabling closer spacing and high-density arrangement while still achieving effective actuation through the varying thickness design of the lower electrode that optimizes electric field 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
The design enhances the durability and driving properties of the liquid-jet head by reducing distortion and electric field concentration, allowing for high-density arrangement of piezoelectric elements and preventing dielectric breakdown.
Implementation Method 1
piezoelectric elements are formed on a surface of this vibration plate, and displacement of the piezoelectric elements allows ink to be ejected
Data Source
AI summary
Provided are, a liquid-jet head capable of enhancing durability thereof when it is driven, and of making an arrangement density of piezoelectric elements high-density, a method of manufacturing the same, and a liquid-jet apparatus. The liquid-jet head includes: piezoelectric elements which are provided on a passage-forming substrate with a vibration plate interposed therebetween, and are respectively configured of a lower electrode, piezoelectric layers and upper electrodes, the passage-forming substrate having pressure generating chambers, which communicate with nozzle orifices for ejecting liquid droplets, formed therein, in which, while the lower electrode is continuously provided across plural piezoelectric elements, near-end portions of the lower electrode at least in regions of the lower electrode between adjacent ones of the piezoelectric elements are formed into thin-thickness portions thinner than portions of the lower electrode in other regions of the lower electrode.