Liquid Ejecting Head Two-Layer Insulating Film
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Solution Overview
Problem
Existing liquid ejecting heads face challenges in achieving high-density piezoelectric elements with thin insulating films, as surface roughness and alignment ratios of the piezoelectric layer are not effectively controlled, leading to limited displacement of the vibration film.
Innovation Solution
A liquid ejecting head design featuring a two-layer insulating film structure, where the lower insulating film is formed by sputtering and the upper insulating film by liquid-phase methods, with different crystal structures but the same material, to increase surface roughness and alignment ratio of the piezoelectric layer, allowing for greater displacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the insulating film thickness is reduced to achieve high-density piezoelectric elements, then the displacement of the vibration film increases, but the surface roughness Ra decreases and the alignment ratio of the piezoelectric layer deteriorates
Solution Approach 1:
The insulating film is divided into two separate layers: a first insulating film (zirconia layer) and a second insulating film (alumina layer). This segmentation allows each layer to perform its specific function - the zirconia layer provides surface roughness for crystal alignment, while the alumina layer provides electrical insulation, enabling the overall film thickness to be reduced without compromising alignment ratio.
Solution Approach 2:
The patent uses a composite structure combining two different insulating materials (zirconia and alumina) with distinct properties. The zirconia layer contributes surface roughness (Ra ≥ 0.5 nm) for piezoelectric layer alignment, while the alumina layer provides additional insulation, creating a composite insulating system that achieves both thin overall thickness and high alignment ratio.
2Productivity
If the insulating film is made thin to increase piezoelectric element density, then the displacement capability improves, but the crystal properties of the piezoelectric layer cannot be controlled effectively
Solution Approach 1:
By segmenting the insulating film into two functional layers, the patent enables independent optimization of each layer's properties. The first insulating film (zirconia) is specifically designed to provide surface roughness for crystal alignment, while the second layer (alumina) provides insulation, allowing thin overall thickness without compromising crystal properties.
Solution Approach 2:
Different regions of the insulating structure are assigned different materials and properties: the first insulating film (zirconia) is optimized for surface roughness and crystal alignment promotion, while the second insulating film (alumina) is optimized for electrical insulation. This local quality differentiation enables effective crystal property control even with reduced overall thickness.
3Device complexity
If a single-layer insulating film is used, then the structure is simple, but the surface roughness Ra cannot be controlled to improve piezoelectric layer alignment
Solution Approach 1:
The insulating film is segmented into two layers with distinct functions. The first layer (zirconia) is specifically engineered to provide surface roughness (Ra ≥ 0.5 nm) that promotes piezoelectric layer alignment, while the second layer (alumina) provides additional insulation. This segmentation achieves high alignment ratio without excessive overall complexity.
Solution Approach 2:
The patent employs a composite insulating film structure combining zirconia and alumina materials. The zirconia layer provides the necessary surface roughness characteristics for crystal alignment, while the alumina layer complements it with insulating properties, creating a composite system that achieves both structural simplicity and manufacturing precision.
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 solution enables a significant increase in displacement of the piezoelectric element while maintaining a thin insulating film, improving crystal properties and alignment ratio, thus enhancing the performance of the liquid ejecting head.
Implementation Method 1
a piezoelectric element, which is displaced by applying a voltage
Implementation Method 2
the lower insulating film formed by a sputtering method
Data Source
AI summary
A liquid ejecting head includes a piezoelectric element that is disposed on a flow passage formation substrate, and discharges liquid from nozzle openings through the nozzle openings by pressurizing the liquid which fills the inside of a pressure generating chamber due to the displacement of a vibration film according to driving of the piezoelectric element, the piezoelectric element includes an insulating film formed on the vibration film, a first electrode film formed on the insulating film, a piezoelectric layer formed on the first electrode film, and a second electrode film formed on the piezoelectric layer, and the insulating film includes a lower insulating film formed on the vibration film and an upper insulating film which is formed on the lower insulating film with the same material as that of the lower insulating film, but has a different crystal structure.