Inkjet Head Protective Layer Layout Against Moisture Deterioration
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Solution Overview
Problem
The absorption of moisture through a polyimide-based protective layer in inkjet heads leads to deterioration of piezoelectric actuators, reducing the reliability and lifespan of the device.
Innovation Solution
A liquid discharge head design with separate first and second protective layers and water-resistant films on these layers, preventing moisture absorption at the circuit connection, thereby protecting the piezoelectric actuator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polyimide-based protective layer is used, then the protective layer provides protection, but moisture is absorbed through the protective layer causing piezoelectric actuator deterioration
Solution Approach 1:
The protective layer is divided into a first protective layer and a second protective layer that are separated from each other. The first protective layer covers the piezoelectric actuator while the second protective layer covers the circuit connection, preventing moisture absorption at the circuit connection area and protecting the piezoelectric actuator from moisture-induced deterioration
Solution Approach 2:
Different protective layers are applied to different areas: the first protective layer (polyimide-based) provides protection for the piezoelectric actuator, while the second protective layer covers the circuit connection area. This local differentiation prevents moisture absorption at the circuit connection while maintaining the protective function over the piezoelectric actuator
2Reliability
If the protective layer has high hygroscopicity, then the protective layer is effective for protection, but the piezoelectric actuator deteriorates due to moisture entry
Solution Approach 1:
The protective layer is segmented into two separate layers: the first protective layer made of polyimide-based resin with high hygroscopicity for protecting the piezoelectric actuator, and the second protective layer for covering the circuit connection. This segmentation prevents moisture from reaching the circuit connection area while maintaining the protective function where needed
Solution Approach 2:
The second protective layer acts as an intermediary barrier between the moisture environment and the circuit connection area. By placing this additional protective layer over the circuit connection, moisture absorption is prevented at this critical area, thereby protecting the overall device reliability
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
Prevents deterioration of piezoelectric performance by isolating the actuator from moisture, extending the life and improving the reliability of the inkjet head.
Implementation Method 1
a piezoelectric actuator is disposed in the nozzle layer... the piezoelectric actuator is disposed adjacent to the nozzle to discharge ink
Data Source
AI summary
A liquid discharge head includes a nozzle layer having a nozzle through which a liquid is discharged from a second side toward a first side, a liquid chamber substrate, and a drive circuit. The nozzle layer includes a vibration layer, a piezoelectric actuator adjacent to the nozzle and over the first side, a circuit connection over the first side, a first protective layer around the circuit connection, a second protective layer over the piezoelectric actuator, a first water-resistant film over the first protective layer, and a second water-resistant film over the second protective layer. The second protective layer is separated from the first protective layer. The first protective layer defines an opening above the circuit connection. The liquid chamber substrate has a liquid chamber communicating with the nozzle. The drive circuit is disposed over the second side and connected to the circuit connection to drive the piezoelectric actuator.