Ionically Conductive Charging Roll Hardness Reduction
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Solution Overview
Problem
Conventional charging rolls with inorganic fillers like calcium carbonate or silica increase hardness, making it challenging to achieve low hardness and high conductivity required for miniaturized and high-performance image forming apparatuses.
Innovation Solution
A charging roll with an ionically conductive elastic layer formed from a rubber composition containing epichlorohydrin rubber and/or nitrile rubber, using peroxide cross-linking instead of sulfur vulcanization, and excluding electron-conductive agents like carbon black, which allows for lower hardness and improved resistance to permanent set while maintaining conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If inorganic fillers like calcium carbonate or silica are added to the rubber composition, then moldability and grindability are improved, but the hardness of the conductive elastic layer increases
Solution Approach 1:
The invention extracts and removes the inorganic filler component from the rubber composition. By formulating a rubber composition that relies on the intrinsic properties of ion-conductive rubber and appropriate additives rather than inorganic fillers, the patent eliminates the source of hardness increase while maintaining moldability through optimized rubber compound formulation and processing conditions
Solution Approach 2:
The invention changes the chemical composition parameters of the rubber material by selecting specific ion-conductive rubbers (epichlorohydrin rubber, nitrile rubber) and controlling the composition ratios of rubber components and additives. This parameter optimization allows achieving both good moldability and low hardness without relying on inorganic fillers
2Ease of manufacture
If inorganic fillers like calcium carbonate or silica are added to the rubber composition, then grindability is improved, but the hardness of the conductive elastic layer increases
Solution Approach 1:
The invention removes inorganic fillers from the composition and achieves grindability through alternative means such as optimizing the rubber compound formulation and controlling vulcanization conditions to produce a uniformly cross-linked structure that is easier to grind while maintaining low hardness
Solution Approach 2:
The invention uses a composite rubber system combining ion-conductive rubber with carefully selected additives and cross-linking agents to achieve the desired balance of grindability and low hardness, replacing the traditional filler-based approach with a polymer-based solution
3Productivity
If conventional injection molding method is used with ion-conductive rubber composition, then production efficiency is improved, but the surface property of the molded body deteriorates
Solution Approach 1:
The invention optimizes the injection molding parameters such as injection temperature, injection pressure, and molding time to achieve both high production efficiency and excellent surface properties. By carefully controlling these process parameters, the patent enables conventional injection molding to produce molded bodies with smooth surfaces and good dimensional accuracy
Solution Approach 2:
The invention uses a specially formulated rubber composition with optimized component ratios and additive packages that improves flow characteristics and surface finish during injection molding, allowing efficient production while maintaining high surface quality
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 results in a charging roll with lower hardness and excellent resistance to permanent set, along with improved conductivity, eliminating the need for chamfering and reducing the requirement for post-cross-linking grinding or polishing, thus enhancing the surface smoothness and performance.
Implementation Method 1
using peroxide cross-linking instead of sulfur vulcanization
Implementation Method 2
a so-called roll charging method has been widely adopted, in which an image bearing medium such as a photosensitive drum and a charging roll are mutually rotated, while the image bearing medium is held in contact with an outer circumferential surface of the charging roll, thereby charging the surface of the image bearing medium
Data Source
AI summary
A charging roll includes a shaft and an ionically conductive elastic layer formed around the shaft. The ionically conductive elastic layer is formed of a rubber composition free of any electron-conductive agent and containing 0.7 to 1.0 parts by weight of a peroxide cross-linking agent per 100 parts by weight of an ion-conductive rubber. The ion-conductive rubber is formed of at least one of an epichlorohydrin rubber and a nitrile rubber, and a percentage of a rubber component in the ionically conductive elastic layer measured by thermogravimetric analysis is 90% or more by weight.