Thermal Head Resin Layer Adhesion
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Solution Overview
Problem
Conventional thermal heads face issues with protective layer separation due to thermal expansion coefficient differences between the first electrode and the inorganic protective layer, leading to stress concentration and potential separation.
Innovation Solution
A thermal head design that incorporates a resin layer between the first electrode and the protective layer, with the resin layer having a portion inserted in the first electrode to enhance adhesion and reduce stress, thereby minimizing the likelihood of protective layer separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a thick first electrode is used to reduce electrical resistance, then electrical resistance decreases, but thermal expansion stress concentrates at the interface between the first electrode and the protective layer, causing separation
Solution Approach 1:
A resin layer is introduced as an intermediary between the first electrode and the protective layer. This resin layer has a thermal expansion coefficient that matches that of the protective layer, thereby reducing thermal expansion stress at the interface and preventing separation while allowing the first electrode to maintain its thick structure for low electrical resistance
Solution Approach 2:
The thermal expansion coefficient parameter is matched between the resin layer and the protective layer. By selecting a resin material whose thermal expansion coefficient corresponds to that of the protective layer, the invention reduces differential thermal expansion stress and prevents interface separation
2Device complexity
If the first electrode and protective layer are directly bonded, then device complexity is reduced, but adhesion strength is insufficient under thermal expansion stress
Solution Approach 1:
The resin layer serves as an intermediary bonding layer between the first electrode and the protective layer. It provides enhanced adhesion strength by chemically or physically bonding to both layers while accommodating thermal expansion differences, thereby strengthening the overall structure
Solution Approach 2:
The resin layer is inserted into grooves or recesses formed in the first electrode surface. This nesting configuration increases the bonding surface area and mechanical interlocking between layers, thereby enhancing adhesion strength without significantly increasing overall device complexity
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 reduces stress at the interface between the first electrode and the protective layer, enhancing adhesion and preventing separation, thus improving the thermal head's reliability and performance.
Implementation Method 1
an increase in thickness of the first electrode gives rise to an appreciable difference in thermal expansion coefficient between the first electrode and a protective layer formed of an inorganic material, and consequently a stress may be concentrated at the interface between the first electrode and the protective layer
Implementation Method 2
a heat generating section; The heat generating section is located on the substrate
Data Source
AI summary
A thermal head according to the present disclosure includes: a substrate; a first electrode; a heat generating section; a second electrode; a resin layer; and a protective layer. The first electrode is located on the substrate. The heat generating section is located on the substrate. The second electrode is located on the substrate so as to be electrically connected to the heat generating section and the first electrode. The resin layer is located on the first electrode. The protective layer is located on the resin layer. Moreover, the resin layer includes a first portion inserted in the first electrode.