Conductive Roller Surface Layer for Charge Leakage Suppression
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Solution Overview
Problem
Existing electrophotographic image forming apparatuses experience charge leakage from toner to developing rollers and charging rollers due to increased processing speeds, leading to image quality deterioration and non-uniform charge injection, despite using ion-conductive elastic layers.
Innovation Solution
An electrophotographic conductive roller with a specific carbon black dispersion in the surface layer, characterized by controlled circle-equivalent diameters and inter-wall distances, is used to reduce charge leakage, comprising a conductive substrate, an ion-conductive elastic layer, and a surface layer with a resin containing polyurethane and carbon black.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a high voltage is applied to the developing blade to charge the toner more quickly in accordance with the increase in processing speed, then the processing speed is improved, but charge leakage from the toner to the developing roller occurs
Solution Approach 1:
The patent applies local quality by creating a surface layer with different electrical resistance properties than the underlying ion-conductive elastic layer. The surface layer has higher volume resistance (1.0×10^10 to 1.0×10^16 Ω·cm) compared to the ion-conductive elastic layer, forming a localized high-resistance zone at the toner contact interface. This local resistance differentiation prevents charge leakage while allowing the bulk material to remain ion-conductive for flexibility and charge injection.
Solution Approach 2:
The patent uses composite materials by combining the ion-conductive elastic layer (providing ion conductivity and flexibility) with a surface layer containing carbon black dispersed in a resin matrix (providing high volume resistance). This composite structure integrates two contrasting material properties: the ion-conductive layer enables charge injection and mechanical compliance, while the carbon black-containing surface layer prevents charge leakage through its high resistance, solving the contradiction between processing speed and charge leakage.
2Object-generated harmful factors
If the surface layer technique is used to suppress charge leakage, then charge leakage is reduced, but image quality degradation such as fogging still occurs due to insufficient electric charge amount
Solution Approach 1:
The patent applies parameter changes by precisely controlling the volume resistance of the surface layer within the range of 1.0×10^10 to 1.0×10^16 Ω·cm and the carbon black content within 1-30 parts by mass relative to 100 parts by mass of resin. These parameter optimizations balance charge leakage suppression with sufficient charge injection capability, preventing both charge leakage and fogging by maintaining the electric charge amount above the design value.
Solution Approach 2:
The surface layer creates a localized high-resistance zone that selectively blocks charge leakage paths between toner and developing roller, while the underlying ion-conductive elastic layer maintains sufficient ion conductivity for charge injection. This local quality differentiation allows simultaneous achievement of charge leakage suppression and adequate charge amount for image quality.
3Object-affected harmful factors
If a peripheral speed difference is provided between the photosensitive drum and the charging roller to prevent drum contamination, then contamination is suppressed, but the amount of charge injected from the charging roller to the photosensitive drum increases causing charging non-uniformity
Solution Approach 1:
The patent applies parameter changes by controlling the surface layer volume resistance and carbon black dispersion characteristics to achieve uniform charge distribution. The specific resistance range (1.0×10^10 to 1.0×10^16 Ω·cm) and carbon black inter-wall distance (80.0 to 150.0 nm) ensure uniform electrical properties across the surface, preventing charging non-uniformity even when peripheral speed differences are applied for contamination prevention.
4Object-generated harmful factors
If carbon black with smaller particle size is used in the surface layer, then charge leakage is suppressed, but manufacturing precision requirements increase due to strict control of circle-equivalent diameter and inter-wall distance
Solution Approach 1:
The patent applies parameter changes by defining specific ranges for carbon black properties: circle-equivalent diameter (60.0 nm or less with σc/Rc of 0.000 to 0.650) and inter-wall distance (80.0 to 150.0 nm with σd/d of 0.000 to 0.600). These parameter specifications balance charge leakage suppression with manufacturability, providing clear fabrication guidelines that achieve the desired performance without excessive 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 solution effectively suppresses charge leakage, maintaining image quality and uniform charge distribution, thereby preventing fogging and ensuring stable image density.
Implementation Method 1
the carbon black in the surface layer having an arithmetic mean Rc of circle-equivalent diameters of 60.0 nm or less and a σc/Rc of 0.000 to 0.650, where σc (nm) is a standard deviation of the circle-equivalent diameters
Implementation Method 2
forming a developing roller using an ion-conductive elastic layer
Data Source
AI summary
An electrophotographic conductive roller including, in this order, a conductive substrate, an ion-conductive elastic layer, and a surface layer, the surface layer includes a resin and carbon black, and the carbon black in the surface layer has an arithmetic mean Rc of circle-equivalent diameters of 60.0 nm or less and a σc/Rc of 0.000 to 0.650, where σc (nm) is a standard deviation of the circle-equivalent diameter. The carbon black in the surface layer has an arithmetic mean d of inter-wall distances of 80.0 to 150.0 nm and a σd/d of 0.000 to 0.600, where σd (nm) is a standard deviation of inter-wall distances.