Piezoelectric Liquid Discharge Head Stress Layout for Plate Deflection

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Solution Overview

Problem

Existing liquid discharge heads face inefficiencies due to excessive deflection of the vibration plate when the piezoelectric element is not driven, limiting displacement and discharge efficiency.

Innovation Solution

A liquid discharge head design with a vibration plate that includes an elastic film and an insulating film, where the insulating film is provided only in the active region and not in the inactive region, and the film stresses satisfy the relation Y < 4.0X + 4800, enhancing the displacement efficiency of the vibration plate.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Force

If the vibration plate is in a state of being deflected toward the pressure chamber when the piezoelectric element is not driven, then the vibration plate can be pre-positioned for discharge, but the displacement amount of the vibration plate reaches the limit even when an attempt is made to displace the vibration plate by driving the piezoelectric element

Engineering Contradiction:

Improvepre-deflection forceVSAvoiddisplacement amount

Core Design Contradiction:

ForceVSLength of moving object

Solution Approach 1:

The insulating film is selectively provided only in the active region where the piezoelectric element is located, while being omitted from the inactive region. This creates local structural differences that allow the active region to have controlled stress for pre-deflection, while the inactive region provides structural support without excessive deflection, resolving the contradiction between pre-positioning capability and displacement range.

Inventive Principle:

Principle #3Local quality

2Productivity

If the insulating film is provided only in the active region and not in the inactive region, then the displacement efficiency is improved, but the manufacturing precision requirement increases due to selective film formation

Engineering Contradiction:

Improvedischarge efficiencyVSAvoidfilm formation precision

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The vibration plate is divided into an active region (where the piezoelectric element is located) and an inactive region (where no piezoelectric element is located). The insulating film is selectively formed only in the active region, allowing different stress characteristics in different regions. This segmentation enables the inactive region to maintain structural integrity while the active region achieves optimal displacement efficiency.

Inventive Principle:

Principle #1Segmentation

3Productivity

If the film stresses satisfy the relation Y < 4.0X + 4800, then the displacement efficiency is enhanced, but the stress balance control complexity increases

Engineering Contradiction:

Improvedisplacement efficiencyVSAvoidstress balance control

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent establishes a quantitative relationship between the film stresses of the elastic film (X) and insulating film (Y) through the inequality Y < 4.0X + 4800. By controlling the stress parameters within this defined range, the patent optimizes the pre-deflection state and displacement efficiency while providing a clear guideline for manufacturing process control.

Inventive Principle:

Principle #35Parameter changes

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 improves displacement efficiency by reducing excessive deflection and maintaining optimal stress balance, thereby enhancing the discharge efficiency of the liquid discharge head.

Implementation Method 1

a piezoelectric element having a first electrode, a piezoelectric body, and a second electrode; a vibration plate configured to apply a pressure to a liquid in the pressure chamber by vibrating when the piezoelectric element is driven

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

the vibration plate includes an elastic film provided on the pressure chamber substrate, and an insulating film provided between the elastic film and the piezoelectric element

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 3

the film stresses satisfy the relation Y < 4.0X + 4800, enhancing the displacement efficiency of the vibration plate

Methodology Applied

Scientific EffectFilm stress:

Data Source

PatentUS12552164B2Liquid discharge head and liquid discharge apparatus

Publication Date: 2026.02.17 SEIKO EPSON CORP

AI summary

There is provided a liquid discharge head including: a piezoelectric element; a pressure chamber substrate provided with a pressure chamber; and a vibration plate configured to apply a pressure to a liquid in the pressure chamber, in which the vibration plate includes an elastic film and an insulating film, the elastic film is provided in each of an active region and an inactive region of the vibration plate, and the insulating film is provided in the active region of the vibration plate and is not provided in a part of the inactive region of the vibration plate, and Y<4.0X+4800, where a compressive stress is represented as a negative value, a tensile stress is represented as a positive value, a film stress of the insulating film is X [MPa], and a film stress of the elastic film is Y [MPa].