Liquid Ejection Head Venting Structure for Adhesive Reliability
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Solution Overview
Problem
The increase in size of liquid ejection head substrates leads to higher adhesive usage, increasing costs and potential adhesive breakage due to thermal expansion, affecting electric reliability.
Innovation Solution
A liquid ejection head design with a first adhesive applied in the outer peripheral region and through holes that allow communication between a space surrounded by the cover member, support member, and adhesive, preventing trapped air expansion and reducing adhesive usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If adhesive is applied over the entire region between support member and cover member, then electric reliability is improved by preventing air bubble formation, but adhesive cost increases significantly
Solution Approach 1:
The patent divides the adhesive application region into two parts: (1) adhesive applied only at the peripheral portion of the support member, and (2) a sealing material applied over the entire region including the peripheral portion. This segmentation allows the adhesive to be placed only where structurally necessary for bonding, while the sealing material provides comprehensive coverage for sealing and preventing air bubble formation, thereby reducing adhesive cost while maintaining electric reliability
Solution Approach 2:
The sealing material serves multiple functions: it seals the entire region between the support member and cover member, prevents air bubble formation, provides thermal insulation, and protects the adhesive at the peripheral portion. By using the sealing material for these multiple purposes, the patent eliminates the need to apply adhesive over the entire region, reducing adhesive usage while maintaining electric reliability
2Reliability
If adhesive is applied over the entire region between support member and cover member, then sealing performance is improved, but adhesive breakage due to thermal expansion increases
Solution Approach 1:
The patent applies a sealing material over the entire region including the peripheral portion where adhesive is applied. This sealing material acts as a cushioning layer that absorbs and distributes thermal expansion stresses, preventing concentrated stress on the adhesive bonds. By providing this protective cushioning beforehand, the patent prevents adhesive breakage due to thermal expansion while maintaining comprehensive sealing performance
Solution Approach 2:
The patent uses a composite structure combining adhesive and sealing material: the adhesive provides strong bonding at the peripheral portion, while the sealing material provides comprehensive sealing and stress distribution. This composite approach leverages the complementary strengths of both materials to achieve both excellent sealing performance and resistance to thermal expansion-induced breakage
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
Enhances electric reliability while minimizing adhesive use, preventing adhesive breakage due to thermal expansion, and reducing manufacturing costs.
Implementation Method 1
The support member and the cover member are connected to each other with an adhesive, and the adhesive fills the gap between the support member and the cover member of the liquid ejection head
Implementation Method 2
the adhesive may break as a result of thermal expansion of the closed spaces in a process of curing the adhesive by applying heat
Data Source
AI summary
A liquid ejection head includes an element substrate, an electric wiring board, a cover member, and a support member having a first through hole, a second through hole, and a support surface. The element substrate includes an ejection port and a pressure chamber to supply liquid to the ejection port. The cover member is joined to the support surface with a first adhesive. The support member supports the element substrate and the electric wiring board on the support surface. The first through hole serves as a flow passage through which the liquid is supplied to the pressure chamber and the second through hole opens in the support surface. The first adhesive is disposed in an outer peripheral region of the support surface of the support member. A space surrounded by the cover member, the support member, and the first adhesive communicates with the second through hole.