Piezoelectric Inkjet Head Insulating Layer Design
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Solution Overview
Problem
Piezoelectric ink jet recording heads face issues with electrode damage, shorts between electrodes, and slow response times due to high electrostatic capacity, particularly when using lead zirconate titanate (PZT) as a piezoelectric member, which leads to inaccurate ink discharge.
Innovation Solution
A liquid discharge head design featuring plural pressure chambers with layered piezoelectric elements, including lower and upper electrodes, and an insulating layer covering the lower electrodes between pressure chambers to prevent damage and shorts, while reducing electrostatic capacity and enhancing response speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a Pt electrode is employed as a lower electrode and chlorine gas is used for processing, then etching capability is improved, but considerable etching of the Pt electrode occurs causing electrode damage
Solution Approach 1:
An insulating layer is introduced as an intermediary between the Pt lower electrode and the piezoelectric member. This insulating layer acts as a protective barrier that prevents the Pt electrode from being etched by chlorine gas during processing, while still allowing the etching gas to effectively process the piezoelectric member above it.
Solution Approach 2:
The insulating layer is formed on the lower electrode before the piezoelectric member is processed. This preliminary protective action ensures that when chlorine gas is subsequently introduced for piezoelectric member processing, the Pt electrode is already protected and will not suffer considerable etching.
2Ease of manufacture
If the lower electrode is exposed during etching of the piezoelectric member, then etching access is improved, but metal is sputtered and attached to the end face causing shorts between electrodes
Solution Approach 1:
The insulating layer serves as a mediator that allows etching access to the piezoelectric member while simultaneously preventing metal sputtering from reaching the end face. The etching gas can access the piezoelectric member through the insulating layer without causing direct exposure of the Pt electrode to sputtering conditions.
3Reliability
If piezoelectric members with high dielectric constant are used, then piezoelectric performance is improved, but electrostatic capacity increases causing slow response speed
Solution Approach 1:
The insulating layer is selectively positioned between the lower electrode and the piezoelectric member, creating a local modification of the electrical field distribution. This localized change reduces the electrostatic capacity in the critical region between electrodes while maintaining the high dielectric constant piezoelectric material's performance in its functional 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
The solution provides a reliable liquid discharge head with improved voltage resistance, durability, and accurate discharge control, enabling faster and more precise ink droplet formation.
Implementation Method 1
when a predetermined voltage is applied to the piezoelectric thin film, the film either stretches or contracts. As the piezoelectric thin film stretches or contracts, the vibration plate film vibrates with the piezoelectric thin film, generating a pressure pulse in ink
Data Source
AI summary
A liquid discharge head according to the present invention comprises plural pressure chambers for applying pressure to liquid, which respectively communicate with liquid discharge openings for discharging liquid; and plural piezoelectric elements, arranged respectively corresponding to the plural pressure chambers, which respectively include lower electrodes, piezoelectric layers and upper electrodes layered in order from the pressure chambers, the lower electrodes being extended to areas corresponding to areas between the plural pressure chambers, and wherein an insulating layer is provided so as to cover at least all the lower electrodes located in the areas corresponding to areas between the plural pressure chambers.