Gradient Coated Electrophotographic Carrier for Stable Charging
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Solution Overview
Problem
Existing electrophotographic carriers, particularly those using iron powder, suffer from unstable frictional charging properties and increased fog in images due to declining carrier resistance over time, leading to reduced image density and carrier adhesion issues.
Innovation Solution
A resin-coated electrophotographic carrier with a concentration gradient of charge control particles and low-resistive particles, where the initial carrier resistance is maintained between 5×10^8-3×10^10 Ωcm, stabilizing carrier resistance and charging ability through a structured layer composition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conductive carrier made of oxidized or non-oxidized iron powder is used, then the carrier provides good initial charging properties, but the frictional charging property becomes unstable and fog is generated after long-term use due to declining carrier resistance
Solution Approach 1:
The patent uses a composite structure consisting of a conductive core material (iron powder) coated with an insulating resin layer. This composite structure combines the advantages of both materials: the conductive core provides initial charging properties while the insulating coating prevents excessive charge loss, maintaining stable frictional charging properties throughout the carrier's service life.
Solution Approach 2:
The patent adjusts the resistance parameter of the carrier by controlling the thickness and composition of the insulating resin coating. By optimizing the coating to have specific resistance characteristics, the carrier maintains stable charging properties over extended use without generating fog, resolving the contradiction between initial performance and long-term reliability.
2Object-generated harmful factors
If the carrier resistance is increased to prevent adhesion, then carrier adhesion is reduced, but the frictional charging property becomes unstable and image density is lowered
Solution Approach 1:
The patent applies local quality by creating a layered structure where the inner core remains highly conductive for stable charging, while the outer insulating coating provides resistance to prevent adhesion. This spatial differentiation of electrical properties allows the carrier to simultaneously maintain stable charging properties and resist adhesion throughout its service life.
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 carrier maintains stable resistance and charging ability over long use, preventing carrier adhesion and image defects, ensuring high-definition image formation without deterioration.
Implementation Method 1
a concentration of the low-resistive particles grows higher toward a surface of the layer from an inner part of the layer
Implementation Method 2
toner particles charged with a polarity opposite that of the latent image are attracted via electrostatic attraction, and adhered onto the electrostatic latent image
Data Source
AI summary
An objective is to provide a highly durable carrier for a developer which is capable of forming a high-definition image stably with no deterioration of a developing property since the carrier resistance and the charging ability remain stable even though the developer is used for a long duration; a method of manufacturing the carrier; and an image forming method employing the same. Disclosed is an electrophotographic carrier comprising a carrier core material and provided thereon, a resin-coated layer comprising charge control particles and low-resistive particles, wherein an initial carrier resistance is 5×108-3×1010 Ωcm; a concentration of the low-resistive particles grows higher toward a surface of the layer from an inner part of the layer; and a concentration of the charge control particles grows lower toward a surface of the layer from an inner part of the layer.