Charging Roller Resistivity for Uniform Image Bearing Surface Potential
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Solution Overview
Problem
Electrographic image forming apparatuses face issues with charge irregularity, leading to minute image irregularities such as spots and streaks due to non-uniform charging of the image bearing member's circumferential surface by the charger, which conventional charging rollers fail to address effectively.
Innovation Solution
An image forming apparatus with a charging roller that charges the image bearing member's surface to a positive polarity, featuring a conductive substrate with a single-layer photosensitive layer containing charge generating, hole transport, and electron transport materials, and a surface layer on the charging roller with a volume resistivity of at least 13.0 log Ω·cm, ensuring uniform charging and inhibiting charge irregularity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional charging roller is used to charge the image bearing member, then the charging process can be completed, but charge irregularity occurs causing spots and streaks on the image
Solution Approach 1:
The patent changes the electrical resistance parameter of the charging roller's surface layer by specifying a volume resistivity of 1.0×10^12 to 1.0×10^14 Ω·cm. This parameter optimization enables uniform charge distribution across the image bearing member surface, eliminating spots and streaks while maintaining effective charging.
Solution Approach 2:
The charging roller employs a composite structure with a base layer and a surface layer having specific resistivity properties. This composite design combines the mechanical integrity of the base layer with the electrical control capabilities of the surface layer, achieving both structural stability and uniform charging performance.
2Reliability
If the surface layer of the charging roller has high volume resistivity, then charge irregularity is inhibited, but the charging efficiency may be reduced
Solution Approach 1:
The patent optimizes the volume resistivity parameter to a specific range (1.0×10^12 to 1.0×10^14 Ω·cm) that balances charge uniformity and charging efficiency. This parameter tuning ensures that the surface layer maintains sufficient insulation to prevent charge irregularity while allowing adequate charge transfer to the image bearing member.
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 inhibits the occurrence of ghost images and charge irregularities by ensuring uniform charging of the image bearing member, even with direct contact charging, while maintaining the surface potential of the photosensitive member within desired limits.
Implementation Method 1
The photosensitive layer contains a charge generating material, a hole transport material, an electron transport material
Data Source
AI summary
An image forming apparatus includes an image bearing member and a charging roller that charges a circumferential surface of the image bearing member to a positive polarity. The image bearing member includes a conductive substrate and a photosensitive layer of a single layer, and satisfies formula (1) shown below. The photosensitive layer contains a charge generating material, a hole transport material, an electron transport material, and a binder resin.0.60≦V(Q/S)×(d/ɛr·ɛ0)(1)In formula (1), Q represents a charge amount [C] of the circumferential surface of the image bearing member, S represents a charge area [m2] of the charged circumferential surface of the image bearing member, d represents a film thickness [m] of the photosensitive layer, co represents vacuum permittivity [F/m], and V represents a value calculated in accordance with formula V=V0−Vr.