Charging Roller Surface Layer for Stable Long-Term Microdischarge
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Solution Overview
Problem
In electrophotographic apparatuses, charging members with surface roughened by fine particles experience wear and changes in charging performance over time due to repeated contact, leading to unstable charging and potential image defects.
Innovation Solution
A charging member with an electro-conductive support, an elastic layer containing high-molecular-weight polyethylene particles exposed from the surface, and a surface layer made of a high-molecular compound with a specific constitutional unit, which maintains the surface shape and prevents particle detachment, ensuring consistent charging performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fine particles are incorporated into the surface layer to roughen the surface, then the adhesion of developer is reduced and discharge is stabilized, but the surface layer wears gradually and fine particles fall off, causing charging performance to change with time
Solution Approach 1:
The invention changes the molecular weight parameter of the polyethylene from conventional low molecular weight to high molecular weight (weight-average molecular weight of 200,000 or more). This parameter change fundamentally alters the wear resistance and mechanical strength of the surface layer, allowing it to maintain its roughened surface structure and embedded fine particles over extended service periods without gradual wear and particle detachment.
Solution Approach 2:
The invention creates a composite surface layer structure combining high-molecular-weight polyethylene with inorganic fine particles. The high-molecular-weight polyethylene matrix provides exceptional mechanical strength and wear resistance, while the embedded inorganic fine particles provide the desired surface roughness and developer release properties. This composite structure ensures both the structural integrity and functional performance of the charging member surface over time.
2Reliability
If the surface layer is made softer to improve contact with the photosensitive member, then charging uniformity is improved, but the surface shape changes more easily due to wear
Solution Approach 1:
The invention changes the molecular weight parameter of the polyethylene to high molecular weight (200,000 or more), which fundamentally alters the material properties. The resulting surface layer achieves a unique combination of properties: it remains sufficiently soft to conform to and maintain uniform contact with the photosensitive member surface, while simultaneously possessing exceptional wear resistance that prevents surface shape changes and maintains dimensional stability over time.
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 changes in charging performance over long-term use, reduces toner adhesion, and stabilizes image quality by maintaining a consistent surface shape and contact area with the photosensitive member.
Implementation Method 1
the elastic layer holds polyethylene particles in such a manner that at least a part of the polyethylene particles are exposed from the elastic layer
Implementation Method 2
a voltage is applied to a roller-shaped charging member arranged in contact with a surface of a drum-shaped photosensitive member to cause microdischarge to occur in the vicinity of a nip therebetween, thereby electrostatically charging the surface of the photosensitive member
Data Source
AI summary
There is provided a charging member having charging performance that is not easily changed even by long-term use.The charging member includes an electro-conductive support, an elastic layer, and a surface layer. The elastic layer contains particles in such a manner that at least a part of the particles are exposed from the elastic layer, and thus a surface of the elastic layer is roughened. The particles are high-molecular-weight polyethylene particles. The surface of the elastic layer is covered with the surface layer in such a manner that the surface shape of the elastic layer is reflected in the surface shape of the charging member. The surface layer contains a high-molecular compound having a specific constitutional unit.