Piezoelectric Liquid Ejection Head with Lead Diffusion Barrier

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Solution Overview

Problem

The diffusion of lead from the piezoelectric film to the lower electrode in liquid ejection heads, such as those used in piezoelectric ink jet printers, increases the electric resistance of the lower electrode, leading to reduced performance of the piezoelectric element.

Innovation Solution

A liquid ejection head design with a first electrode, piezoelectric layer, and second electrode laminated in a specific order, where the first electrode is disposed in two regions: one region overlapping with both the piezoelectric layer and second electrode, and another region overlapping only with the vibration plate, with a first mixture layer containing lead and the electrode material to inhibit lead diffusion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a piezoelectric element with a lower electrode, piezoelectric film, and upper electrode is used, then the liquid ejection function is achieved, but lead diffusion from the piezoelectric film to the lower electrode increases electric resistance and lowers performance

Engineering Contradiction:

Improveperformance of piezoelectric elementVSAvoidlead diffusion to lower electrode

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

An intermediate layer is introduced between the piezoelectric film and the lower electrode. This intermediate layer acts as a diffusion barrier that prevents lead from the piezoelectric film from diffusing into the lower electrode, thereby maintaining low electric resistance while preserving the piezoelectric element's performance

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent employs composite material structure by combining the piezoelectric film containing lead with a specially designed intermediate layer material that has properties preventing lead diffusion. This composite structure allows the system to maintain the necessary piezoelectric functionality while blocking the harmful lead diffusion to the lower electrode

Inventive Principle:

Principle #40Composite materials

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

Prevents lead diffusion to the first electrode, maintaining low electrical resistance and enhancing the performance of the piezoelectric element by preventing a rise in resistance.

Implementation Method 1

A liquid ejection apparatus, typified by a piezoelectric ink jet printer, uses a liquid ejection head that ejects liquid such as ink

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS20250276524A1Liquid ejection head

Publication Date: 2025.09.04 SEIKO EPSON CORP

AI summary

A liquid ejection head has a piezoelectric element and a vibration plate, and a first electrode, a piezoelectric layer, and a second electrode of the piezoelectric element are laminated in this order in a lamination direction directed from the vibration plate to the piezoelectric element. The first electrode is disposed in a first region and a second region, the first region being a region where the first electrode, the piezoelectric layer, and the second electrode overlap when seen in the lamination direction, the second region being a region where the first electrode overlaps with neither the piezoelectric layer nor the second electrode but overlaps with the vibration plate. A first mixture layer is provided on the first electrode in the second region, the first mixture layer being formed of a mixed material containing lead and a material forming the first electrode.