Thermal Print Head Wiring Layer Segmentation for Thermal Stress Reduction
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Solution Overview
Problem
Conventional thermal print heads lack durability and reliability, which affects the quality and efficiency of thermal printing processes.
Innovation Solution
A thermal print head design featuring a substrate made of single crystal semiconductor with a resistive layer and a wiring layer that includes conductive and heat generating sub-parts, where the conductive part has a lower resistance value per unit length than the heat generating part, and the heat generating sub-part has a resistance value between the two, all disposed on a ridge structure, to reduce thermal stress and improve durability and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional thermal print head design is used, then the structure is simple, but the durability and reliability are insufficient
Solution Approach 1:
The wiring layer is segmented into conductive parts and heat generating sub-parts with different resistance values. The heat generating sub-part is positioned between the heat generating part and conductive part, creating a graduated resistance structure that reduces thermal stress and improves reliability without significantly increasing overall device complexity.
Solution Approach 2:
Different regions of the wiring layer are assigned different resistance characteristics. The conductive part has lower resistance for efficient current flow, while the heat generating sub-part has intermediate resistance to reduce temperature gradients. This local differentiation of properties enhances durability and reliability.
2Reliability
If heat generating parts are directly connected to conductive parts, then the structure is simple, but temperature gradients and thermal stress increase
Solution Approach 1:
The heat generating sub-part acts as an intermediary element between the heat generating part and the conductive part. This intermediate structure with intermediate resistance value smooths the temperature gradient and reduces thermal stress, preventing direct thermal shock that would occur with immediate connection.
Solution Approach 2:
The resistance parameter is gradually changed across the wiring layer structure. By introducing a heat generating sub-part with resistance value between that of the heat generating part and conductive part, the patent creates a gradual parameter transition that reduces thermal stress and improves reliability.
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 enhances the durability and reliability of thermal print heads by reducing temperature gradients and thermal stress, improving print quality, energy efficiency, and extending the lifespan of the print head while maintaining printing efficiency.
Implementation Method 1
electric current is passed to the resistive layer to cause the heat generating parts to generate heat
Implementation Method 2
The heat is transferred to a print medium (e.g., a thermal recording paper), so that the color of the print medium changes to form an image
Data Source
AI summary
A thermal print head includes a substrate, a resistor layer and a wiring layer. The substrate is made of a single crystal semiconductor and includes an obverse surface facing in one sense of a thickness direction. The resistive layer is supported by the substrate and includes a plurality of heat generating parts arranged side by side in a main scanning direction. The wiring layer is supported by the substrate and forms a conductive path to the plurality of heat generating parts. The wiring layer includes a conductive part and a heat generating sub-part for each of the plurality of heat generating parts, where the conductive part has a lower resistance value per unit length in a sub-scanning direction than the heat generating part, and where the heat generating sub-part has a resistance value per unit length in the sub-scanning direction that falls between the respective resistance values of the heat generating part and the conductive part. The substrate includes a ridge raised from the obverse surface and extending in the main scanning direction. The heat generating part, the heat generating sub-part and the conductive part are disposed on the ridge. The heat generating sub-part is located between the heat generating part and the conductive part in the sub-scanning direction.