Charging Member Surface Roughness for Toner Adhesion Control
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Solution Overview
Problem
Existing charging members in electrophotographic image forming apparatuses face challenges in maintaining uniform charging performance over time due to toner and external additives accumulation, leading to image unevenness.
Innovation Solution
A charging member with a roughened surface, featuring an electroconductive elastic layer containing a vulcanized product of a rubber composition with a butadiene skeleton, and insulating particles, which creates a surface potential gradient that promotes the movement of toner and external additives, preventing their accumulation and stabilizing the surface potential of the photosensitive member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the surface of the charging member is smoothened to decrease friction, then the adhesion of toner and external additives is suppressed, but the charging performance becomes unstable over time due to accumulation of toner and external additives
Solution Approach 1:
The charging member surface is designed with non-uniform roughness characteristics, creating local variations in surface properties that prevent uniform accumulation of toner and external additives, thereby maintaining stable charging performance over time
Solution Approach 2:
Instead of smoothening the surface to reduce adhesion, the invention inverts the approach by intentionally creating surface roughness. This roughened surface prevents adhesion accumulation and maintains charging stability, achieving the opposite of conventional wisdom
2Object-generated harmful factors
If a fluorine resin is used in the surface layer to prevent adhesion, then the friction is decreased, but the charging performance deteriorates due to accumulation of toner and external additives with increased printing
Solution Approach 1:
The invention changes the surface roughness parameter from smooth to rough, and specifies a particular hardness range (20-80° on JIS scale) for the elastic layer, creating optimal conditions for preventing adhesion accumulation while maintaining charging performance consistency
3Reliability
If the surface roughness is increased to prevent adhesion accumulation, then the charging performance is maintained, but the friction between charging member and photosensitive member increases
Solution Approach 1:
The surface roughness is controlled within specific parameters (Spk 0.5-5.0 μm, Svk 0.5-3.0 μm, Sk 1.0-10.0 μm) to create local variations that prevent adhesion accumulation while maintaining overall friction characteristics within acceptable ranges for proper charging function
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 effectively maintains high charging performance and prevents image unevenness by ensuring the toner and external additives are moved to specific areas on the charging member, maintaining a stable surface potential and image quality over a long period.
Implementation Method 1
creates a surface potential gradient that promotes the movement of toner and external additives
Implementation Method 2
an electroconductive elastic layer which is a surface layer formed on the electroconductive support
Data Source
Figure 1
Figure 2~3
Figure 4~5B
AI summary
It is intended to provide a charging member capable of maintaining high charging performance even when used over a long period. The charging member has an electroconductive support and an electroconductive elastic layer as a surface layer, wherein the electroconductive elastic layer has a roughened surface, and the electroconductive elastic layer has an average Martens' hardness Mc of 2 N/mm2 or larger and 20 N/mm2 or smaller measured with an indentation strength of 0.04 mN at a core surface defined according to three dimensional surface texture standard (ISO 25178-2:2012), and has an average viscosity Vc of 70 mV or smaller measured in a 2 µm square field of view under a scanning probe microscope.