Liquid Discharge Head Interlayer Design for Adhesion and Bubble Stability
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Solution Overview
Problem
Conventional liquid discharge heads face issues with the flow path forming member peeling off from the Si substrate due to ink flow and solvent swelling, leading to poor ink discharge and potential corrosion, which affects image formation and the longevity of the device.
Innovation Solution
A liquid discharge head with an interlayer of thermoplastic resin between the Si substrate and the flow path forming member, and a protection layer made of metal covering the energy generating element and exposed regions, preventing peeling and corrosion while maintaining bubble stability for improved ink discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an interlayer is interposed between the Si substrate and the flow path forming member to prevent peeling, then adhesion strength is improved, but a step is formed on the Si substrate that deforms bubbles and causes remaining bubbles in the pressure chamber
Solution Approach 1:
The interlayer is selectively positioned only in specific regions (first region corresponding to the energy generating element and second region corresponding to the flow path region on the pressure chamber side) while avoiding the central region where bubbles are generated. This local quality approach allows the interlayer to provide adhesion strength where needed without interfering with bubble formation and stability in the critical discharge region.
Solution Approach 2:
The interlayer is divided into multiple discrete regions rather than being continuous. It is segmented into a first region around the energy generating element and a second region in the flow path area, with intentional gaps between these regions. This segmentation prevents the formation of large steps that would deform bubbles while maintaining adhesion in critical areas.
2Reliability
If the interlayer surrounds the energy generating element while avoiding its upper surface, then peeling is suppressed, but steps deform bubbles and cause remaining bubbles that affect next discharge
Solution Approach 1:
The interlayer is strategically placed in local regions where peeling is most likely to occur (around the energy generating element and in the flow path region) while deliberately avoiding the central discharge region. This localized placement suppresses peeling in critical areas without creating steps that would interfere with bubble formation and discharge at high frequencies.
3Strength
If the interlayer is laid only in ground region avoiding pressure chamber and flow path, then peeling is prevented, but Si-based members are exposed to ink causing dissolution and corrosion
Solution Approach 1:
The interlayer acts as an intermediary protective barrier between the ink and the Si-based members. By positioning the interlayer in the first region (around the energy generating element) and second region (flow path region), it prevents ink from contacting and corroding the Si substrate and energy generating element, while still allowing adhesion function to operate effectively.
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 effectively prevents peeling and corrosion, ensuring consistent ink discharge and extending the life of the liquid discharge head by maintaining the integrity of the flow path and protecting the Si-based components from ink contact.
Implementation Method 1
an interlayer formed of thermoplastic resin which has adhesiveness to the Si substrate higher than the flow path forming member and which can hold the flow path forming member
Implementation Method 2
an electrothermal conversion element such as a heater... ink close to the energy generating element 3 bubbles by being instantaneously heated and boiled due to drive of the energy generating element 3
Implementation Method 3
a protection layer including metal which is formed so as to cover the element in order to protect the element... protecting the Si-based components from ink contact
Data Source
AI summary
A liquid discharge head includes a substrate having an element that discharges liquid by generating thermal energy to generate an air bubble in the liquid, and a liquid supply port for supplying the liquid to the element, and a flow path forming assembly including a flow path forming member having a discharge port for discharging the liquid and, between the substrate and the flow path forming member, a pressure chamber including the element disposed adjacent thereto and a flow path causing the pressure chamber and the liquid supply port to communicate with each other. In addition, an interlayer is provided on a joining portion of the substrate and the flow path forming member and provided so as to protrude from between the substrate and the flow path forming member into the flow path, and a protection layer including metal is formed so as to cover the element. The interlayer is not disposed on a boundary portion between the pressure chamber and the flow path, and the protection layer is disposed at least on the boundary portion.