Liquid Ejection Head Corner Design to Suppress Adhesive Creep-Up
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Solution Overview
Problem
In liquid ejection heads, adhesive squeeze-out onto the walls of flow passages and support substrates can lead to clogging of individual flow channels due to capillary forces, impairing liquid ejection performance.
Innovation Solution
The liquid ejection head design includes a channel substrate and a support substrate bonded via an adhesive, with corner portions of the common flow channel having angles larger than 90° to reduce capillary force and prevent adhesive creep-up.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If adhesive is used to bond the channel substrate and support substrate, then the substrates are securely joined, but adhesive squeeze-out occurs on partition walls and support substrate corners
Solution Approach 1:
The harmful adhesive squeeze-out is extracted and removed from the bonding process by applying adhesive only to specific safe zones (margins) away from partition walls and corners, preventing contamination of flow passages
Solution Approach 2:
The adhesive application is made local and selective by defining specific bonding margins (e.g., 10-50 μm from partition walls, 50-100 μm from corners) where adhesive is permitted, creating different adhesive presence zones across the substrate surface
2Reliability
If adhesive is applied generously to ensure complete bonding coverage, then bonding reliability improves, but capillary force causes adhesive to creep up corner portions
Solution Approach 1:
The geometric parameters of corner portions are changed by forming rounded corners with radii of 5-50 μm instead of sharp corners, which reduces capillary force and prevents adhesive creep-up while maintaining bonding reliability
Solution Approach 2:
Different treatments are applied to different locations: rounded corners at vulnerable positions versus straight edges elsewhere, and selective adhesive application zones that avoid corner regions entirely
3Area of stationary object
If adhesive creeps up onto partition walls and corner portions, then bonding area increases, but individual flow channels become clogged
Solution Approach 1:
Adhesive application is extracted from vulnerable areas by establishing safety margins (10-50 μm from partition walls, 50-100 μm from corners) where adhesive is explicitly excluded, preventing flow channel clogging
Solution Approach 2:
The bonding structure is divided into adhesive-permitted zones (safe margins) and adhesive-excluded zones (near partition walls and corners), with each zone having different adhesive presence characteristics
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 design effectively suppresses adhesive creep-up and clogging in individual flow channels, ensuring reliable liquid supply and maintaining high liquid ejection performance.
Implementation Method 1
the adhesive is more likely to creep up on the corner portion due to capillary force attributable to surface tension of the adhesive
Data Source
AI summary
A liquid ejection head comprises a liquid ejection substrate for ejecting a liquid, wherein the liquid ejection substrate includes a flow passage forming substrate and a support substrate which is bonded to the flow passage forming substrate via an adhesive, the flow passage forming substrate includes a common flow channel which communicates with a flow passage formed in the support substrate and an individual flow channel which communicates with the common flow channel, and among a corner portion of an end portion of the common flow channel, an angle of the corner portion which is closest to the individual flow channel is larger than 90°.