Selective Electrochemical Kogation Removal in Inkjet Print Heads

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Solution Overview

Problem

In inkjet printing, the uneven thermal conduction caused by kogation adherence on the upper protective layer of heat generating resistor elements leads to unstable bubble formation and reduced ink ejection velocity, affecting print quality and accuracy.

Innovation Solution

A liquid ejecting head with a protective member that can be selectively voltage-activated to elute kogation from each heat generating resistor element, using an electrochemical reaction to remove deposits based on the adhesion level, thereby maintaining optimal thermal conduction and print quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the upper protective layer is made of iridium or ruthenium to protect the heat generating resistor element, then the protective layer can be dissolved by electrochemical reaction to remove kogation, but the surface dissolution removes the protective function and shortens the lifespan of the print head

Engineering Contradiction:

Improveprint qualityVSAvoidlifespan of print head

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The patent divides the protective layer into multiple independent segments, each corresponding to a specific heat generating resistor element. This allows selective application of voltage to dissolve kogation only from specific segments that require cleaning, rather than dissolving the entire protective layer. The segmentation enables localized maintenance while preserving the protective function in other areas.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements local quality by making each segment of the protective layer independently controllable. Different segments can have different states - some segments maintain their protective function while others undergo electrochemical dissolution to remove kogation. This localized approach ensures that the protective layer's function is preserved in areas where it is needed while allowing cleaning in areas where kogation has accumulated.

Inventive Principle:

Principle #3Local quality

2Manufacturing precision

If voltage is applied to dissolve kogation from the protective layer, then print quality is restored, but the protective layer is consumed and durability is reduced

Engineering Contradiction:

Improveink landing accuracyVSAvoiddurability of protective layer

Core Design Contradiction:

Manufacturing precisionVSDuration of action of stationary object

Solution Approach 1:

The patent introduces a dynamic control mechanism that allows the system to switch between two states for each protective layer segment: a protective state where the layer remains intact, and a cleaning state where voltage is applied to dissolve kogation. This dynamic switching enables the system to adapt to different operational conditions and only consume the protective layer when necessary for maintaining print quality.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent implements a selective discarding and recovering strategy where the protective layer is temporarily sacrificed (discarded) in specific segments to remove kogation and restore print quality. After cleaning, the protective function is recovered in those segments since the electrochemical reaction removes both the kogation and a thin layer of the protective material, which then reforms or is replenished. This approach minimizes overall consumption by only discarding what is necessary.

Inventive Principle:

Principle #34Discarding and recovering

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 solution ensures efficient removal of kogation deposits, maintaining print quality and extending the lifespan of the print head by preventing unnecessary dissolution of the protective layer, thus enhancing the durability and accuracy of inkjet printing.

Implementation Method 1

the surface is dissolved by an electrochemical reaction, thus removing the kogation adhering to the surface of the upper protective layer

Methodology Applied

Scientific EffectElectrochemical reaction: Electrolysis

Implementation Method 2

heat generating resistor elements that are arranged in a manner corresponding to each of the pressure chambers, and can heat the liquid reserved in the pressure chambers

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 3

a system for ejecting liquid by use of generation of bubbles produced by thermal energy generated by a heat generating resistor element in liquid

Methodology Applied

Scientific EffectBubble formation by thermal energy: Boiling

Data Source

PatentUS9114612B2Liquid ejecting head, substrate for liquid ejecting head, and printing apparatus

Publication Date: 2015.08.25 CANON KK

AI summary

A print head includes upper protective members located at positions corresponding to heat generating resistor elements to protect the heat generating resistor elements, and further, a part of the protective member can be eluted into ink when a current flows inside in a state in which the ink is stored in the pressure chambers. The print head includes a drive element and a logic circuit capable of allowing a current to independently flow in each of the upper protective layers so as to elute a part of the upper protective layer, in which the current flows, into the ink.