Piezoelectric Diaphragm Tension Difference Control
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Solution Overview
Problem
Existing liquid ejecting heads with piezoelectric diaphragms face issues with cracking due to stress differences between compressive and tensile films as nozzle pitches narrow, leading to diaphragm thinning and potential damage.
Innovation Solution
A liquid ejecting head design with a diaphragm composed of layers including a compressive silicon dioxide film, a tensile zirconium dioxide film, and a corrosion-resistant film, where the tension difference between these layers is minimized to reduce distortion and cracking, with specific thickness and stress ranges to enhance mechanical strength and prevent damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the diaphragm is thinned to accommodate narrower nozzle pitches, then the productivity and resolution are improved, but the reliability deteriorates due to cracking from tension difference between layers
Solution Approach 1:
The patent changes the physical parameters of the diaphragm layers by controlling the thickness of each layer (first layer: 0.5-5 μm, second layer: 0.1-2 μm) and adjusting their stress characteristics. This parameter optimization reduces the tension difference between layers while maintaining the thin diaphragm structure needed for narrow nozzle pitches, thereby preventing cracking and maintaining reliability.
Solution Approach 2:
The patent uses a composite structure consisting of two different materials: a first layer made of silicon dioxide (SiO2) with compressive stress, and a second layer made of zirconium dioxide (ZrO2) with tensile stress. This composite material approach allows the diaphragm to be thin enough for high-resolution nozzles while the combination of materials with opposing stresses counteracts tension differences and prevents cracking.
2Strength
If multiple layers with different stresses are combined to form the diaphragm, then the mechanical strength is improved, but the device complexity increases
Solution Approach 1:
The patent employs a homogeneous manufacturing process using standard semiconductor fabrication techniques (sputtering, chemical vapor deposition) to create the multi-layer structure. By using uniform processing methods for both layers and integrating the piezoelectric elements in a systematic manner, the complexity of fabricating the layered structure is reduced while still achieving the desired mechanical strength enhancement.
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 effectively reduces the tension difference between layers, minimizing distortion and cracking in the diaphragm, allowing for efficient ink ejection and maintaining mechanical strength even with narrower nozzle pitches.
Implementation Method 1
a liquid ejecting head that ejects a liquid inside pressure chambers through nozzles by vibrating a diaphragm with piezoelectric elements
Implementation Method 2
The elastic film is a compressive film formed of silicon dioxide. The insulating film is a tensile film formed of zirconium dioxide
Data Source
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AI summary
A liquid ejecting head including a diaphragm constituting a portion of a wall surface of a pressure chamber that accommodates a liquid, and a piezoelectric element that vibrates the diaphragm. In the liquid ejecting head, the diaphragm includes a plurality of layers, and the plurality of layers include a compressive film that has compressive stress and a tensile film that has tensile stress. The compressive film and the tensile film are two layers adjacent to each other that have a largest tension difference among the plurality of layers, and an absolute value of the tension difference between the compressive film and the tensile film is 400 [N/m] or smaller.