Piezoelectric Device Moisture Barrier Design

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Solution Overview

Problem

Piezoelectric devices, such as ink jet recording heads, face issues with moisture-induced changes in vibration plate characteristics due to reactions between zirconium oxide and humidity, leading to decreased performance and potential breakage, especially with thin second electrode configurations and moisture barrier layer placement in active portions.

Innovation Solution

A piezoelectric device design featuring a vibration plate with a zirconium oxide layer and a moisture barrier layer made of a different material, where the moisture barrier is positioned outside the active portion and not overlapping with it, to prevent moisture penetration and maintain deformation capabilities while protecting the vibration plate from humidity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If a recessed portion is provided in the piezoelectric layer to improve displacement characteristics, then the displacement amount increases at low voltage, but the vibration plate becomes exposed or close to external atmosphere causing moisture reaction with zirconium oxide

Engineering Contradiction:

Improvedisplacement amount at low voltageVSAvoidvibration plate characteristic stability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

A moisture barrier layer is introduced as an intermediary substance between the vibration plate (containing zirconium oxide) and the external atmosphere. This layer prevents direct contact between moisture and zirconium oxide, blocking the harmful chemical reaction while allowing the recessed portion structure to remain intact for improved displacement characteristics.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The moisture barrier layer creates a protective environment around the vibration plate, effectively isolating the zirconium oxide from reactive moisture in the atmosphere. This inert barrier prevents the chemical reaction that would otherwise degrade the vibration plate's piezoelectric properties.

Inventive Principle:

Principle #39Inert atmosphere (Inert environment)

2Productivity

If the second electrode is made thin to increase active portion density, then productivity increases, but moisture easily permeates through the second electrode causing vibration plate characteristic changes

Engineering Contradiction:

Improveactive portion densityVSAvoidvibration plate characteristic stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The moisture barrier layer is selectively positioned only in the arm portion region where it is needed for protection, while leaving the active portion region uncovered to maintain electrical functionality. This localized application allows thin second electrodes in active portions without compromising overall reliability.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The moisture barrier layer serves as an intermediary protective layer that prevents moisture permeation through the thin second electrode, allowing high active portion density while maintaining vibration plate stability.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If a moisture barrier layer is provided in the active portion region to prevent moisture reaction, then vibration plate reliability improves, but the displacement amount of the piezoelectric element decreases

Engineering Contradiction:

Improvevibration plate characteristic stabilityVSAvoiddisplacement amount

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The moisture barrier layer is applied selectively only in the arm portion region outside the active portions, leaving the active portion regions uncovered. This localized differentiation allows the arm portions to be protected from moisture while the active portions maintain their full deformation capability for liquid ejection.

Inventive Principle:

Principle #3Local quality

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 configuration enhances the displacement characteristics of the piezoelectric element by preventing moisture-induced changes in the vibration plate's characteristics, allowing for high-density active portion placement and maintaining the integrity of the vibration plate under humid conditions.

Implementation Method 1

a piezoelectric element that has a first electrode provided on the one surface side of the substrate via the vibration plate, a piezoelectric layer provided on the first electrode, and a second electrode provided on the piezoelectric layer

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

a first moisture barrier layer formed of a material other than the zirconium oxide is formed in a region of the vibration plate opposite to the substrate and overlapping a bottom surface of the second recessed portion

Methodology Applied

Scientific EffectMoisture barrier:

Data Source

PatentUS10751996B2Piezoelectric device, liquid ejecting head, and liquid ejecting apparatus

Publication Date: 2020.08.25 SEIKO EPSON CORP

AI summary

A piezoelectric device includes in a piezoelectric layer, a recessed portion which is provided outside an active portion and opens on the side opposite to a substrate is provided, in a lamination direction of the substrate and a piezoelectric element, a first barrier layer formed of a material other than the zirconium oxide is formed in a region of a vibration plate opposite to the substrate and overlapping a bottom surface of the recessed portion, and the first barrier layer is not formed in a portion of a region overlapping the active portion in the lamination direction.