Liquid Ejection Head Adhesive Uniformity via Repellent Barrier
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Solution Overview
Problem
Existing liquid ejection heads face challenges in uniformly covering piezoelectric elements with adhesive, leading to variations in adhesive amount and diaphragm hardness, which affects the driving consistency of piezoelectric elements during substrate joining.
Innovation Solution
A liquid repellent portion is formed around the piezoelectric elements using a material that repels adhesive, ensuring consistent adhesive distribution and preventing excessive adhesive from reaching the elements during substrate joining, allowing for denser arrangement of pressure chambers with reduced driving variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If adhesive is applied to join substrates, then substrate joining is achieved, but adhesive flows along the side of the lead-out wire causing non-uniform coverage and varying diaphragm hardness
Solution Approach 1:
A liquid repellent layer is introduced as an intermediary between the adhesive and the piezoelectric element sides. This layer acts as a mediator that selectively repels the adhesive, preventing it from flowing onto the piezoelectric element sides while allowing the adhesive to properly join the substrates. The liquid repellent layer thus resolves the contradiction by enabling substrate joining without the harmful adhesive flow.
Solution Approach 2:
The liquid repellent layer is applied selectively only to specific regions where piezoelectric elements are located, while other areas remain without this layer to allow proper adhesive bonding. This local differentiation creates zones with different adhesive affinity, ensuring uniform adhesive coverage in bonding areas while preventing overflow onto piezoelectric elements.
2Adaptability or versatility
If adhesive amount varies on piezoelectric element sides, then substrate joining flexibility is maintained, but diaphragm hardness becomes uneven causing piezoelectric element driving variation
Solution Approach 1:
The liquid repellent layer serves as a protective intermediary that shields the piezoelectric element sides from adhesive contamination. By preventing adhesive from accumulating on these sides, it ensures uniform diaphragm hardness and consistent piezoelectric element driving characteristics, thereby improving reliability while maintaining the flexibility of substrate joining through the adhesive.
3Productivity
If piezoelectric elements are densely arranged, then ejection port density increases, but adhesive flow control becomes more difficult
Solution Approach 1:
The liquid repellent layer is formed in advance on the piezoelectric element sides before the substrate joining process. This preliminary action pre-establishes protective barriers that control adhesive flow paths, enabling dense arrangement of piezoelectric elements without compromising adhesive flow control during the subsequent joining process.
Solution Approach 2:
The liquid repellent layer acts as a spatial intermediary that defines clear boundaries for adhesive flow. This allows piezoelectric elements to be densely arranged while the repellent layers maintain controlled adhesive zones, preventing overflow even in high-density configurations.
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 consistent piezoelectric element driving characteristics by preventing adhesive from influencing the diaphragm, allowing for denser pressure chamber arrangement and reduced variations in driving performance.
Implementation Method 1
A liquid repellent portion surrounding the piezoelectric element is disposed on a surface of the first substrate where the piezoelectric element is disposed
Data Source
AI summary
A liquid ejection head includes a first substrate and a second substrate. The first substrate includes a pressure chamber communicating with an ejection port that ejects liquid, a diaphragm that forms part of a wall constituting the pressure chamber, and at least one piezoelectric element configured to generate energy for displacing the diaphragm to eject liquid through the ejection port. The second substrate has a cavity containing the piezoelectric element. The first substrate and the second substrate are joined together with an adhesive. A liquid repellent portion surrounding the piezoelectric element is disposed on a surface of the first substrate where the piezoelectric element is disposed.