Electroconductive Member Surface Layer for Uniform Charging
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Solution Overview
Problem
Existing electroconductive members for electrophotography face challenges in maintaining uniform charging of photosensitive members, particularly in cleaner-less systems, due to issues like contamination adhesion, injection charging, and potential unevenness, which affect image quality and durability.
Innovation Solution
An electroconductive member with a surface layer containing specific polyurethane resin structures and optimized volume resistivity and hardness is developed, incorporating structures represented by certain structural formulas, to suppress injection charging and ensure consistent charging performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a circumferential speed difference is provided between the charging member and the photosensitive member to reduce contamination adhesion, then contamination adhesion is reduced, but injection charging increases causing charging unevenness
Solution Approach 1:
The invention changes the material parameters of the charging member by incorporating a polyurethane resin with specific volume resistivity (1.0×10^10 to 1.0×10^16 Ω·cm) and controlled hardness (1.0 to 7.0 N/mm² at 1μm depth). These parameter changes suppress injection charging while maintaining the ability to uniformly charge the photosensitive member, resolving the contradiction between reducing contamination adhesion and maintaining charging uniformity
Solution Approach 2:
The charging member uses a composite structure combining a polyurethane resin base material with specific molecular structures (containing groups represented by formulas (1), (2), and/or (3)). This composite material approach provides both the necessary mechanical properties and electrical resistance characteristics to prevent both contamination adhesion and injection charging, simultaneously addressing both harmful effects
2Manufacturing precision
If a hydrophobic surfactant is added to the surface layer of the charging roller to suppress injection charging, then injection charging is suppressed initially, but the effect disappears after increased number of sheets due to surfactant migration or decomposition
Solution Approach 1:
Instead of using a hydrophobic surfactant that migrates or decomposes over time, the invention employs a polyurethane resin with inherently stable molecular structures that maintain their charge suppression function throughout extended operation. The resin's molecular architecture (containing specific hydrocarbon groups with 3-9 carbon atoms) provides long-term stability without degradation, ensuring consistent charging uniformity across thousands of sheets
Solution Approach 2:
The invention changes from using a surfactant additive to using a polyurethane resin with specifically controlled volume resistivity (1.0×10^10 to 1.0×10^16 Ω·cm) and hardness parameters. These parameter changes create a stable, non-migrating material that maintains charging suppression function over time, resolving the reliability issue while preserving charging uniformity
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 prevents injection charging and maintains uniform charging of photosensitive members, enhancing image quality and durability over time by reducing contamination adhesion and potential unevenness.
Implementation Method 1
a surface layer which has a volume resistivity of 1.0×10^10 Ω·cm or more and 1.0×10^16 Ω·cm or less... contains a polymer having a urethane linkage, the polymer having, in a molecule, structures of at least two groups selected from the following three groups of structures (A), (B), and (C)
Implementation Method 2
when a charging member of a contact charging system is applied to the cleaner-less system
Implementation Method 3
the transfer residual toner is triboelectrically charged by the charging member, with the result that it is electrostatically difficult for the transfer residual toner to migrate to the surface of the charging member
Implementation Method 4
a fine gap region in which a discharge occurs, the region being formed by the charging sheet and the photosensitive member brought into contact with each other
Data Source
AI summary
Provided is an electroconductive member for electrophotography having a stable charging ability. The electroconductive member includes, in this order, an electroconductive substrate, an electroconductive elastic layer, and a surface layer. The surface layer contains a polymer having a urethane linkage. The polymer has, in the molecule, structures included in at least two groups selected from: Group A of structures each represented by a specific structural formula (1); Group B of at least one of structures each represented by a specific structural formula (2) or structures each represented by a structural formula (3); and Group C of structures each represented by a specific structural formula (4). The surface layer has a volume resistivity of 1.0×1010 Ω·cm or more and 1.0×1016 Ω·cm or less, and the surface layer has a universal hardness at a depth 1 μm from the surface thereof of 1.0 N/mm2 or more and 7.0 N/mm2 or less.