Electroconductive Roll Surface Curvature for Uniform Discharge
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Solution Overview
Problem
Image forming apparatuses face challenges in achieving uniform image quality due to uneven discharge between the charging roll and the photoconductor element, which is influenced by the surface roughness of the charging roll.
Innovation Solution
An electroconductive roll with a core member, a rubber base material, and a surface layer having an arithmetic mean peak curvature of 1,880 to 14,024 (1/mm) is developed, where the surface layer includes an electroconductive matrix with dispersed insulating particles to enhance surface roughness and ensure uniform discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the surface roughness of the charging roll is increased to improve discharge uniformity, then image quality improves, but the surface becomes too rough causing non-uniform discharge and image unevenness
Solution Approach 1:
The invention changes the surface roughness parameter from conventional values (Rz 3-15 μm) to a specific range (Rz 6-12 μm with Spc 1,880-14,024 1/mm) to optimize discharge uniformity. This precise parameter control resolves the contradiction by finding the optimal balance point where sufficient roughness enables uniform discharge without excessive roughness causing image unevenness
Solution Approach 2:
The surface layer is constructed as a composite material containing resin particles (5-20 μm diameter) dispersed in a binder resin, creating a multi-component structure that achieves the desired surface roughness profile. This composite structure allows simultaneous achievement of adequate roughness for discharge uniformity while maintaining smooth enough surfaces to prevent image unevenness
2Reliability
If fine particles are added to the surface layer to control discharge, then discharge uniformity improves, but the surface roughness becomes excessive leading to image defects
Solution Approach 1:
The invention specifies precise parameters for fine particles: diameter of 5-20 μm, with the resin particle diameter to binder resin thickness ratio controlled at 0.5-2.0. These parameter constraints ensure particles provide sufficient roughness for uniform discharge while preventing excessive roughness that would cause image defects
Solution Approach 2:
The surface layer is designed with non-uniform particle distribution and varying local roughness characteristics. The arithmetic mean peak curvature Spc is controlled at 1,880-14,024 1/mm, creating localized surface features that promote uniform discharge at the micro-level while maintaining overall surface smoothness for image quality
Data Source
AI summary
An electroconductive roll includes a core member, a rubber base material disposed around the core member, and a surface layer disposed around the rubber base material. The arithmetic mean peak curvature Spc of a surface of the surface layer is equal to or greater than 1,880 (1/mm), and is equal to or less than 14,024 (1/mm).