Electroconductive Roller Surface Layer for Contaminant Repulsion
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Solution Overview
Problem
In electrophotographic apparatuses, contaminants such as toner and external additives adhere to electroconductive rollers, leading to uneven image density and reduced durability due to electrostatic adhesion, especially in cleaner-less systems where toner residues are positively charged, causing them to easily adhere to charging rollers.
Innovation Solution
An electroconductive member with a surface layer composed of a binder resin and electroconductive fine particles, where the fine particles are exposed to form protruded portions, providing a volume resistivity between 1.0×10^10 Ω·cm and 1.0×10^16 Ω·cm, and a universal hardness of 1.0 N/mm² to 7.0 N/mm², allowing for efficient charge injection and reduced contaminant adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a DC voltage is applied to the electroconductive roller to enable charging function, then the charging capability is improved, but electrostatic adhesion of positively charged contaminants to the roller surface increases
Solution Approach 1:
The patent inverts the charging polarity of the electroconductive roller from positive to negative. By applying a negative DC voltage, the roller surface becomes negatively charged, which causes positively charged contaminants (toner, external additives) to be repelled rather than attracted. This inversion of the electric field direction fundamentally changes the interaction from adhesive to repulsive, solving the contamination problem while maintaining charging functionality.
Solution Approach 2:
The patent converts the harmful electrostatic adhesion effect into a beneficial repulsion effect. The same electrostatic principle that causes contamination (electrostatic attraction between oppositely charged surfaces) is inverted to create electrostatic repulsion. The negative charge on the roller surface, which could be considered a modification to the standard positive charging approach, actually benefits the system by actively repelling positively charged contaminants, turning a potential harm into a protective mechanism.
2Object-affected harmful factors
If the surface of the electroconductive roller is coated with fluorine compound or silicone compound to reduce contaminant adhesion, then anti-contamination property is improved, but the coating durability and image quality may deteriorate
Solution Approach 1:
The patent replaces the mechanical/chemical coating approach (fluorine or silicone compounds) with an electrical field-based solution. Instead of relying on low-surface-energy coatings that can wear off or affect image quality, the invention uses the electrostatic field generated by negative charging to repel contaminants. This substitution of the contamination prevention mechanism from surface chemistry to electrostatics eliminates the durability and image quality issues associated with coatings.
Solution Approach 2:
The patent changes the key parameter of the electroconductive roller from surface composition (coating materials) to electrical property (charging polarity). By shifting the control parameter from what the surface is made of to how the surface is charged, the invention achieves contaminant repulsion without the drawbacks of coatings. The volume resistivity and surface potential are optimized to ensure effective repulsion while maintaining charging function.
3Manufacturing precision
If the particle diameter of toner is reduced to increase image quality and speed, then image resolution is improved, but the amount of contaminant depositing on the charging member increases
Solution Approach 1:
The patent converts the increased contamination problem resulting from smaller toner particles into a benefit through electrostatic repulsion. The negative charge on the roller surface creates an electrostatic barrier that repels positively charged fine toner particles and external additives. This turns the previously harmful effect (increased adhesion of fine particles) into a protective effect, allowing high-resolution imaging with fine particles without the associated contamination issues.
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 contaminant adhesion to the charging roller, maintaining image quality and extending the lifespan of electrophotographic apparatuses by ensuring contaminants are negatively charged and returned to the photosensitive member, independent of use conditions.
Implementation Method 1
the surface layer contains electroconductive fine particles which are dispersed in the binder resin and have a number average particle diameter of 5.0 nm or more and 50.0 nm or less
Implementation Method 2
the contaminant, such as the toner or the external additive, having an insulating property is affected by sliding and the like in an electrophotographic image-forming apparatus, and thus part thereof has a positive or negative charge. Under the situation in which the potential difference is generated between the surface potentials of the electroconductive roller and the photosensitive member, any one of the positively charged contaminant and the negatively charged contaminant cannot be prevented from electrostatically adhering to the electroconductive roller
Data Source
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AI summary
Provided is an electroconductive member for electrophotography which is suppressed in adhesion of a contaminant to a surface thereof. The electroconductive member for electrophotography includes, in this order, an electroconductive support, an electroconductive elastic layer, and a surface layer. The surface layer contains a binder resin and electroconductive fine particles having a number average particle diameter of 5.0 nm or more and 50.0 nm or less. At least part of the electroconductive fine particles are exposed from the surface layer. The surface layer has, on a surface thereof, protruded portions derived from exposed portions of the electroconductive fine particles. The surface layer has a volume resistivity of 1.0×1010 Ω·cm or more and 1.0×1016 Ω·cm or less and a universal hardness at a depth of 1 µm from the surface thereof of 1.0 N/mm2 or more and 7.0 N/mm2 or less.