Liquid Ejection Head Adhesive Layer for Crack Prevention
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Solution Overview
Problem
The existing liquid ejection heads with high-rigidity sealing members and adhesives are prone to cracking due to thermal expansion differences between the recording element substrate and the support member, leading to stress and potential damage.
Innovation Solution
A liquid ejection head design featuring an adhesive layer with a first adhesive portion of high rigidity and a second adhesive portion of lower rigidity, positioned between the recording element substrate and the support member, and covered by a sealing member, which reduces stress and prevents cracking by allowing for easier movement of the substrate during temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sealing member with higher rigidity is used, then insulation property and liquid penetration prevention are improved, but stress concentration and cracking in the recording element substrate occur due to thermal expansion differences
Solution Approach 1:
The adhesive layer is divided into two regions with different rigidity characteristics: a first adhesive portion with higher rigidity for strong bonding and a second adhesive portion with lower rigidity near the sealing member to accommodate thermal expansion. This local differentiation allows the system to simultaneously achieve strong adhesion and stress relief, preventing cracking while maintaining insulation properties.
Solution Approach 2:
The adhesive layer functions as a composite structure combining materials or regions with different mechanical properties. The first adhesive portion provides high strength bonding, while the second adhesive portion provides flexibility and stress relief. This composite approach enables the adhesive layer to handle both the bonding requirements and the thermal stress accommodation needs of the system.
2Strength
If an adhesive agent with higher rigidity is used, then adhesiveness is enhanced, but stress occurs in the contact surface when temperature changes due to different coefficients of thermal expansion
Solution Approach 1:
The adhesive layer is differentiated into two portions with distinct rigidity characteristics. The first adhesive portion maintains strong adhesion to the recording element substrate, while the second adhesive portion near the sealing member has reduced rigidity to accommodate thermal expansion differences. This local quality variation allows the adhesive layer to provide both strong bonding and stress relief during temperature changes.
Solution Approach 2:
The rigidity parameter of the adhesive layer is varied spatially within the adhesive portion. By changing the rigidity parameter from the first adhesive portion to the second adhesive portion, the system optimizes both adhesion strength and stress accommodation capability, preventing stress concentration that would lead to cracking.
3Stability of the object's composition
If the recording element substrate is firmly fixed to the support member, then structural stability is improved, but cracking occurs during thermal shock due to rigid constraints on thermal expansion
Solution Approach 1:
The adhesive layer provides different degrees of constraint at different locations. The first adhesive portion provides strong constraint for structural stability, while the second adhesive portion provides flexible constraint to accommodate thermal expansion. This local differentiation allows the substrate to remain stably fixed while being able to expand thermally without cracking.
Solution Approach 2:
The adhesive layer transitions from a rigid constraint in the first portion to a flexible constraint in the second portion, allowing dynamic adaptation to thermal changes. This dynamic characteristic enables the structure to maintain stability during normal operation while accommodating thermal expansion during temperature variations, preventing thermal shock damage.
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 design effectively suppresses the occurrence of cracks in the recording element substrate, as demonstrated by thermal shock tests showing no cracks after 100 cycles, compared to comparative examples which cracked within 50-60 cycles.
Implementation Method 1
strong stress occurs in the contact surface between the sealing member and the recording element substrate and the support member when a temperature change occurs because the coefficient of thermal expansion of the recording element substrate and that of the support member are different
Data Source
AI summary
A liquid ejection head including a recording element substrate for ejecting liquid supported by a support member with an adhesive layer provided between the recording element substrate and the support member. A terminal is provided at an end portion of the recording element substrate with a sealing member covering the end portion of the recording element substrate including the terminal. The sealing member is in contact with a side surface of the end portion and an end surface of the adhesive layer. The adhesive layer comprises includes a first adhesive portion and a second adhesive portion positioned between the first adhesive portion and the sealing member. Rigidity of the second adhesive portion is less than the rigidity of the sealing member and less than the rigidity of the first adhesive portion.