Thermal Print Head Protrusion with Embedded Heat Storage

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Solution Overview

Problem

Conventional thermal print heads face challenges in maintaining consistent heat storage properties and printing quality due to variations in the thickness of the protruded glaze formed by screen printing with glass paste, and single-crystal semiconductor protrusions require adequate heat storage without compromising their shape.

Innovation Solution

A thermal print head with columnar heat storage members embedded in a protrusion on the substrate, where the protrusion is formed using anisotropic etching of a single-crystal semiconductor, and the heat storage members are elongated in the thickness direction with inclined outer surfaces to enhance heat retention and uniformity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If screen printing with glass paste is used to form protruded glaze, then heat storage property is provided, but thickness variation occurs leading to inconsistent printing quality

Engineering Contradiction:

Improveheat storage propertyVSAvoidthickness uniformity

Core Design Contradiction:

TemperatureVSManufacturing precision

Solution Approach 1:

The patent replaces the screen printing process (mechanical deposition method) with a semiconductor fabrication process involving photolithography and etching. This substitution enables precise control of the protrusion thickness through photoresist patterning and controlled etching, eliminating the thickness variation inherent in screen printing while maintaining the heat storage function.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the material parameter from glass paste to single-crystal semiconductor material, and changes the formation process parameters from screen printing deposition to photolithography and etching. These parameter changes enable precise thickness control (e.g., 5-20 μm) and uniformity across the protrusion surface, resolving the manufacturing precision issue while preserving heat storage capability.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If anisotropic etching is performed on single-crystal semiconductor to form protrusion, then uniform shape is achieved, but heat storage property becomes insufficient due to better heat conductivity

Engineering Contradiction:

Improveshape uniformityVSAvoidheat storage property

Core Design Contradiction:

Manufacturing precisionVSTemperature

Solution Approach 1:

The patent applies local quality by creating a protrusion with specific geometric characteristics (inclined outer surfaces at controlled angles) that concentrate heat locally at the tip region where heat generating parts are disposed. The single-crystal semiconductor material's better heat conductivity is utilized to distribute heat uniformly across the protrusion base while the inclined geometry concentrates it at the functional region, achieving both shape uniformity and adequate heat storage.

Inventive Principle:

Principle #3Local quality

3Manufacturing precision

If protrusion is formed to have inclined outer surfaces, then uniform heat distribution is achieved, but manufacturing complexity increases

Engineering Contradiction:

Improveheat distribution uniformityVSAvoidprotrusion structure

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent replaces complex multi-step mechanical machining or molding processes with a photolithography-based fabrication approach. The inclined outer surfaces are formed through photolithographic patterning followed by anisotropic etching, which naturally creates the desired angles through crystallographic plane exposure. This substitution simplifies the manufacturing process while achieving precise control over the inclined surfaces for uniform heat distribution.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 provides stable and uniform heat distribution to the heat generating parts, ensuring consistent printing quality and suitability for high-speed printing by preventing heat leakage, regardless of manufacturing variations.

Implementation Method 1

performing anisotropic etching with respect to the obverse surface of the material substrate so that the protrusion is formed to have the top surface and the pair of inclined outer surfaces

Methodology Applied

Scientific EffectAnisotropic etching:

Implementation Method 2

the exposed parts (heat generating parts) of the resistor layer are selectively heated by Joule's effect

Methodology Applied

Scientific EffectJoule's effect: Joule Heating

Implementation Method 3

a protrusion formed on the obverse surface of the substrate and extending in a main scanning direction... columnar heat storage members embedded in the protrusion

Methodology Applied

Scientific EffectHeat storage: Thermal Energy Storage

Data Source

PatentUS11279145B2Thermal print head and method of manufacturing the same

Publication Date: 2022.03.22 ROHM CO LTD

AI summary

A thermal print head includes a substrate; a protrusion formed on an obverse surface of the substrate and extending in a main scanning direction; heat generating parts disposed on a top surface of the protrusion and arranged along the main scanning direction; and columnar heat storage members embedded in the protrusion and disposed in a given area having a width in a sub-scanning direction and being elongated in the main scanning direction. Each of the columnar heat storage members is elongated in a thickness direction of the substrate and has an upper end and a lower end, with the upper end being disposed at the same level of the top surface of the protrusion.