Laminated Piezoelectric Head Structure for Adhesion and Damage Control
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Solution Overview
Problem
Existing piezoelectric elements in liquid ejecting heads face challenges in achieving both strong adhesion between layers and preventing damage, particularly when thin film piezoelectric bodies are laminated, which affects ejection characteristics and reliability.
Innovation Solution
A liquid ejecting head design with a specific lamination order of pressure chamber substrate, diaphragm, common electrodes, and thin film piezoelectric bodies, including an overlapping and non-overlapping region configuration, along with a voltage application circuit to apply reference and driving voltages, enhances adhesion and reduces damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two thin film piezoelectric bodies are laminated to increase displacement per unit voltage, then ejection characteristics are improved at the same voltage or cost is reduced by replacing with lower rated voltage components, but it becomes difficult to achieve both assurance of adhesion to the lower layer of the upper piezoelectric layer and suppression of damage to the upper piezoelectric layer
Solution Approach 1:
The upper surface of the second thin film piezoelectric body is configured with different heights at different locations: a first position in the overlapping region where the second piezoelectric body overlaps all electrodes, and a second position in the non-overlapping region where it overlaps only common electrodes. This local height differentiation creates varied adhesion conditions and stress distribution, ensuring both strong adhesion and damage suppression throughout the structure.
Solution Approach 2:
The asymmetric configuration of the upper surface height creates an uneven stress distribution pattern that prevents uniform damage propagation. The first position (higher) and second position (lower) form an asymmetric profile that optimizes both adhesion strength and damage resistance in the laminated piezoelectric structure.
2Productivity
If thin film piezoelectric bodies are laminated to increase displacement per unit voltage, then ejection characteristics are improved, but the complexity of ensuring both adhesion and damage suppression increases
Solution Approach 1:
Rather than creating a completely complex structure, the invention applies local quality by varying the upper surface height only in specific regions (overlapping vs non-overlapping areas). This localized differentiation achieves the desired ejection characteristics while keeping the overall structure relatively simple and manufacturable.
Solution Approach 2:
The upper surface is segmented into distinct regions with different heights based on the underlying electrode configuration. This segmentation allows each region to serve its specific function (adhesion or damage suppression) while maintaining overall structural simplicity through a systematic division rather than complex integrated design.
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 ejection characteristics and reliability by optimizing the lamination structure and voltage application, ensuring effective ink ejection while maintaining structural integrity.
Implementation Method 1
a piezoelectric element that vibrates a diaphragm that constitutes a part of a wall surface of a pressure chamber is used. The diaphragm is vibrated by the piezoelectric element, and thus the liquid in the pressure chamber is ejected from a nozzle.
Data Source
AI summary
A liquid ejecting head includes: in which when a region in an arrangement direction where the second thin film piezoelectric body overlaps all of the individual electrode, the first common electrode, and the second common electrode when viewed in the lamination direction is defined as an overlapping region, and a region in the arrangement direction where the second thin film piezoelectric body overlaps the first common electrode and the second common electrode and does not overlap the individual electrode when viewed in the lamination direction is defined as a non-overlapping region, a position of an upper surface of the second thin film piezoelectric body in the overlapping region is a first position, and the position of the upper surface of the second thin film piezoelectric body in the non-overlapping region is a second position that is located lower than the first position.