Liquid Ejecting Head Flow Path Design for Bubble Pooling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing liquid ejecting heads face challenges in suppressing liquid or air bubbles from pooling in the flow path, leading to unstable ejection characteristics, especially when nozzle diameters are reduced for higher resolution applications, due to the formation of small steps at the boundaries between flow path plates which can affect liquid ejection.
Innovation Solution
A liquid ejecting head configuration where the flow path is formed from a single substrate with a wider opening area on the pressure chamber side than on the nozzle side, and the cross-sectional area widens in steps towards the pressure chamber side, reducing the step size and pooling risk, and using a silicon single crystal substrate with a (110) plane orientation for precise wet etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the nozzle diameter is reduced to eject smaller amounts of liquid for higher resolution, then the image resolution is improved, but liquid or air bubbles pool more easily at the steps formed by stacked flow path plates, causing ejection instability
Solution Approach 1:
The patent merges multiple flow path formation plates into a single integrated flow path formation substrate. This eliminates the steps formed at boundaries between stacked plates, preventing liquid and air bubbles from pooling. The single substrate structure maintains the necessary flow path geometry while removing the harmful interfaces that cause ejection instability, thus preserving reliability while enabling smaller nozzle diameters for higher resolution.
Solution Approach 2:
The patent transitions from a stacked multi-plate configuration to a single-substrate configuration with a tapered flow path cross-section. The flow path cross-sectional area decreases from the pressure chamber side toward the nozzle side, creating a gradual transition rather than abrupt steps. This dimensional change in the flow path geometry prevents pooling while maintaining the buffer function.
2Area of stationary object
If multiple flow path formation plates are stacked to form the ejection flow path, then the flow path can be formed with larger cross-sectional area, but steps are formed at plate boundaries causing liquid pooling and ejection instability
Solution Approach 1:
The patent combines multiple flow path formation plates into a single flow path formation substrate. This integration eliminates the stepped boundaries that occur when plates are stacked, preventing liquid and air bubbles from pooling at these interfaces. The single substrate maintains the required flow path cross-sectional area while removing the harmful steps, thus ensuring ejection stability.
Solution Approach 2:
The patent applies local quality by creating a tapered flow path cross-section that varies along the flow direction. The flow path has a larger cross-sectional area near the pressure chamber and gradually decreases toward the nozzle, forming gentle slopes rather than abrupt steps. This localized geometric variation prevents pooling while maintaining adequate flow path area for buffer function.
3Area of stationary object
If the flow path cross-sectional area is reduced to minimize steps at plate boundaries, then step size is reduced, but liquid pooling still occurs and ejection characteristics become unstable with smaller nozzles
Solution Approach 1:
The patent integrates multiple flow path formation plates into a single substrate, completely eliminating the stepped boundaries that cause pooling. This merger removes the root cause of the problem rather than merely reducing step size, ensuring that liquid and air bubbles do not pool at plate interfaces, thus maintaining ejection stability even with smaller nozzles.
Solution Approach 2:
The patent changes the flow path geometry from a constant cross-section with abrupt steps to a tapered cross-section that gradually decreases in area from the pressure chamber side toward the nozzle side. This dimensional variation creates gentle slopes that prevent pooling while maintaining adequate flow path area, eliminating the need to reduce the flow path cross-sectional area to minimize steps.
4Ease of manufacture
If positional misalignment between stacked flow path plates occurs, then the flow path shape and step size vary, but this causes unstable liquid ejection characteristics
Solution Approach 1:
The patent combines multiple flow path formation plates into a single flow path formation substrate. This integration eliminates the interfaces between plates where misalignment would occur, thereby eliminating the source of variation in flow path shape and step size. The single substrate ensures consistent ejection characteristics regardless of assembly tolerances, as there are no stacked plates to misalign.
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
This configuration effectively suppresses liquid and air bubbles from pooling, stabilizes liquid ejection, and prevents variations in ejection characteristics caused by positional misalignment, enabling more precise and consistent liquid dispensing.
Implementation Method 1
Liquid in the pressure chambers is ejected from the nozzles through the penetrating flow path by driving piezoelectric elements (a type of actuator)
Implementation Method 2
using a silicon single crystal substrate with a (110) plane orientation for precise wet etching
Data Source
AI summary
A liquid ejecting head includes a pressure chamber formation substrate having a pressure chamber formed therein, a flow path formation substrate that is connected to the pressure chamber formation substrate, and that has a flow path in communication with the pressure chamber formed in a state penetrating through the flow path formation substrate in a thickness direction thereof, and a nozzle plate that is connected to the flow path formation substrate on an opposite side to the pressure chamber formation substrate, and that has a nozzle in communication with the flow path opened therein. The flow path formation substrate is configured from a single substrate, and an opening area on a pressure chamber side of the flow path is formed wider than an opening area on a nozzle side of the flow path.