Liquid Discharge Head Adhesive Bonding with Uneven Substrate Walls

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Solution Overview

Problem

Existing liquid discharge heads face challenges in achieving high adhesive strength when joining substrates using adhesive bonds, which affects the reliability and longevity of the bonding process.

Innovation Solution

The implementation of uneven portions on the surface of the holding substrate, with specific cross-sectional shapes and dimensions, to increase the adhesive area and anchor effect, combined with a surface treatment film to enhance compatibility and resistance to liquid corrosion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a flat surface is used for joining substrates with adhesive bond, then the manufacturing process is simple, but the adhesive strength is insufficient

Engineering Contradiction:
Improveadhesive strengthVSAvoidsurface structure complexity
Core Design Contradiction:
StrengthVSDevice complexity

Solution Approach 1:

The invention applies surface curvature by forming uneven portions (protrusions and recesses) on the joining surface of the holding substrate. This curved/uneven surface structure increases the adhesive strength through mechanical interlocking, directly resolving the contradiction between simple manufacturing and sufficient adhesive strength.

Inventive Principle:
Principle #14Spheroidality (Curvature)

Solution Approach 2:

The invention creates a porous-like structure on the joining surface through the uneven portions (protrusions and recesses). This increased surface roughness and porosity provides more anchoring points for the adhesive, significantly improving adhesive strength while maintaining manufacturing feasibility.

Inventive Principle:
Principle #31Porous materials

2Reliability

If adhesive bond is used to join substrates, then the joining process is simple, but the bond durability against liquid corrosion is insufficient

Engineering Contradiction:
Improvebond durabilityVSAvoidliquid corrosion
Core Design Contradiction:
ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The uneven surface structure with protrusions and recesses creates a mechanical interlocking effect that resists liquid corrosion. The curved surfaces and increased path length prevent liquid from easily penetrating the adhesive bond, thereby improving bond durability against liquid corrosion.

Inventive Principle:
Principle #14Spheroidality (Curvature)

Solution Approach 2:

The uneven portions act as an intermediary structure between the holding substrate and the adhesive bond. This intermediate structure provides both mechanical support and resistance to liquid corrosion, protecting the adhesive bond while maintaining the simplicity of the adhesive joining process.

Inventive Principle:
Principle #24Intermediary (Mediator)

3Strength

If adhesive bond thickness is increased to improve strength, then the adhesive strength increases, but the liquid penetration resistance decreases

Engineering Contradiction:
Improveadhesive strengthVSAvoidliquid penetration
Core Design Contradiction:
StrengthVSObject-affected harmful factors

Solution Approach 1:

The uneven surface structure allows the adhesive bond to form a thicker layer while maintaining liquid penetration resistance. The protrusions and recesses create a tortuous path for liquid, preventing easy penetration even when the overall adhesive thickness is increased for strength.

Inventive Principle:
Principle #14Spheroidality (Curvature)

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 approach significantly improves the adhesive strength and reliability of the bonding process, prolonging the effective duration of the adhesive bond and enhancing the overall performance of the liquid discharge head.

Implementation Method 1

joining a flow path substrate (20) and a holding substrate (50) to each other by means of an adhesive bond (80)

Methodology Applied
Scientific EffectAdhesive bonding: Adhesive

Data Source

PatentEP3424720B1Liquid-discharging head, liquid-discharging unit, and device for discharging liquid
Publication Date: 2020.09.23 RICOH CO LTD
  • EP3424720B1 patent drawingFigure 1
  • EP3424720B1 patent drawingFigure 2
  • EP3424720B1 patent drawingFigure 3

AI summary

A first member is a flow path substrate 20, a second member is a holding substrate 50, a joining surface 20a of a flow path substrate 20 is joined to a joining surface 50a of a holding substrate 50 by an adhesive bond 80, a wall surface 55 of the opening 51 of the holding substrate 50 is a wall surface crossing the joining surface 50a of the holding substrate 50 joined to the joining surface 20a of the flow path substrate 20, an uneven portion 56 is provided on the wall surface 55 of the opening 51 of the holding substrate 50, and a part of the adhesive bond 80 joining the joining surface 20a of the flow path substrate 20 to the joining surface 50a of the holding substrate 50 is embedded in at least a part of the uneven portion 56 of the wall surface 55.