Charging Member Surface Layer for C-Set Image Suppression
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Solution Overview
Problem
Electrophotographic charging members experience permanent compression set (C-set) issues, leading to non-uniform micro-discharge gaps and image density variations, especially under high-temperature and high-humidity conditions, which result in unwanted image artifacts like horizontal black or white lines.
Innovation Solution
A charging member with a conductive support, an elastic layer, and a surface layer containing a specific compound represented by formula (1), which includes a binder and a multi-branched structure with siloxane linkages, reducing moisture absorption and improving dielectric constant and charging ability, thereby minimizing C-set images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a charging roller is used to charge the electrophotographic photosensitive member, then charging function is achieved, but permanent compression set occurs at the contact part after long-term standing, leading to non-uniform micro-discharge gaps and image density nonuniformity
Solution Approach 1:
The charging member uses a composite structure consisting of a foam core layer and a skin layer. The foam core layer provides elasticity and compression resistance, while the skin layer provides surface smoothness and charge uniformity. This composite material approach solves the contradiction by combining materials with complementary properties to prevent both C-set and maintain charging uniformity.
Solution Approach 2:
The patent specifies precise parameter ranges for the foam core layer (density: 0.01-0.06 g/cm³, hardness: 10-30 degrees JIS A, Poisson's ratio: 0.45-0.50) and skin layer (thickness: 1-10 μm, hardness: 30-80 degrees JIS A). By controlling these parameters within specific ranges, the charging member achieves optimal balance between compression resistance and surface uniformity, preventing both C-set and charging nonuniformity.
2Reliability
If the apparatus is left to stand still over a long period of time in high temperature and high humidity environment, then C-set tends to come about more at the contact part of the charging roller
Solution Approach 1:
The patent specifies that the foam core layer should have Poisson's ratio of 0.45-0.50 and the skin layer should have thickness of 1-10 μm with specific hardness range. These parameter specifications ensure the charging member maintains its shape and charging ability even under high temperature and high humidity conditions, resisting environmental degradation.
Solution Approach 2:
The composite structure of foam core layer and skin layer provides resistance to environmental degradation. The foam core layer's high elasticity and the skin layer's protective function work together to prevent C-set progression under harsh environmental conditions, maintaining charging reliability.
3Reliability
If direct-current voltage is applied to the charging member, then charging is achieved, but C-set images occur more frequently due to non-uniform micro-discharge gap
Solution Approach 1:
By specifying the skin layer thickness (1-10 μm) and hardness (30-80 degrees JIS A), the patent ensures the charging surface maintains uniform micro-discharge gaps even under DC voltage application. This parameter control prevents charge accumulation and eliminates the root cause of C-set images, ensuring both charging function and image quality.
Solution Approach 2:
The skin layer provides localized smooth surface quality at the charging interface, ensuring uniform micro-discharge gaps specifically at the contact region with the photosensitive member. This local quality improvement prevents charge accumulation and eliminates C-set images while maintaining overall 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 reduces strain and maintains uniform charging ability, preventing C-set images across various environments, ensuring stable and high-grade electrophotographic image formation.
Implementation Method 1
a surface layer containing a binder and a compound represented by the following formula (1)... which includes a binder and a multi-branched structure with siloxane linkages, reducing moisture absorption
Implementation Method 2
a roller-shaped charging member... kept in contact with the electrophotographic photosensitive member by pressing force of a spring... follow-up rotated with the latter... maintain any uniform micro-discharge gap
Implementation Method 3
a roller-shaped charging member used in contact charging of an electrophotographic photosensitive member
Data Source
Figure 1A~1D
Figure 2A~3B
Figure 4~5
AI summary
Provided are a charging member, process cartridge, and electrophotographic device that suppress C-set images, which occur when the charging member and an electrophotographic photoreceptor remain in contact over a long period of time. A specific compound is included in the surface layer of the charging member, which has an electroconductive support body and a surface layer.