Magnetic Carrier Magnetization Control for Electrophotographic Developer
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Solution Overview
Problem
Existing electrophotographic developers face issues with carrier adhesion, image quality, and durability due to reduced magnetization and frictional electrification, especially in small-size devices, leading to defects like image defects, fogging, and toner spent on the carrier surface.
Innovation Solution
A magnetic carrier comprising spherical composite core particles of ferromagnetic iron oxide fine particles and a cured phenol resin, with a melamine resin coating layer, is developed, optimizing particle size, magnetization, and electric resistance to prevent carrier adhesion and maintain image quality over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the particle size of the carrier is reduced to form a dense magnetic brush, then the flowability and image quality are improved, but the magnetization of individual carrier particles is reduced, causing carrier adhesion to the photoreceptor
Solution Approach 1:
The patent applies parameter changes by optimizing the particle size distribution of the carrier to a specific range (0.5-20 μm with most particles between 1-5 μm) and controlling the magnetization parameters (saturation magnetization σ0 and residual magnetization σ1 within specific ranges). This resolves the contradiction by finding the optimal balance point where small particles form dense magnetic brushes while maintaining sufficient magnetization to prevent carrier adhesion to the photoreceptor.
2Use of energy by moving object
If the agitation intensity is enhanced to improve frictional electrification between toner and carrier, then the charging efficiency is improved, but the stress on the developer increases, causing toner to adhere onto the carrier surface
Solution Approach 1:
The patent applies parameter changes by optimizing the particle size distribution and surface properties of the carrier to achieve effective frictional electrification at moderate agitation intensities. The controlled magnetization and surface characteristics enable sufficient charging efficiency without requiring excessive agitation that would cause toner adhesion to the carrier surface.
3Volume of moving object
If the particle size of the carrier is reduced for use in small-size developing devices, then the device size is reduced, but the constraint force of the magnetic carrier on the developing sleeve becomes small, promoting carrier adhesion
Solution Approach 1:
The patent applies composite materials by creating a carrier with a specific composition including ferromagnetic particles (Fe, Fe3O4, γ-Fe2O3) combined with binder resins in controlled ratios. This composite structure enables small particle sizes for compact devices while maintaining sufficient magnetization and constraint force through the synergistic combination of magnetic particles and binder materials.
4Use of energy by moving object
If the toner uses low-molecular weight resin for low-temperature fixing, then the energy consumption is reduced, but the toner is spent on the carrier surface under high-temperature and high-humidity conditions during continuous use
Solution Approach 1:
The patent applies parameter changes by optimizing the carrier surface properties and magnetization parameters to reduce toner-carrier interaction under high-temperature and high-humidity conditions. The controlled surface characteristics and magnetic properties prevent toner spent even when using low-molecular weight resin toners for low-temperature fixing, maintaining developer durability during continuous use.
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 magnetic carrier reduces magnetization dispersion, enhances durability, and prevents carrier adhesion, ensuring high-quality images are produced for a long period by controlling the melamine resin coating layer and maintaining desired electric charge and resistance values.
Implementation Method 1
spherical composite core particles consisting of ferromagnetic iron oxide fine particles and a cured phenol resin
Implementation Method 2
The carrying particles called a magnetic carrier act for imparting an appropriate positive or negative electrical quantity to the toner by frictional electrification
Implementation Method 3
act for transferring the toner through a developing sleeve accommodating magnets therein into a developing zone near the surface of the photoreceptor on which the latent image is formed, by using a magnetic force of the magnets
Implementation Method 4
a toner that is charged into a polarity reverse to that of the latent image is attached onto the latent image by an electrostatic force to develop the latent image
Data Source
AI summary
The present invention relates to a magnetic carrier for an electrophotographic developer comprising spherical composite core particles comprising at least ferromagnetic iron oxide fine particles and a cured phenol resin, and having an average particle diameter of 20 to 60 µm, the magnetic carrier for an electrophotographic developer satisfying the formula (1): σ1 - σ0 = -2 to 0 wherein σ0 represents a saturation magnetization (Am2/kg) of the carrier particles having a particle diameter in the vicinity of the average particle diameter of the magnetic carrier for an electrophotographic developer; and σ1 represents a saturation magnetization (Am2/kg) of the carrier particles having a particle diameter of less than 20 µm, and a two-component system developer using the magnetic carrier. The two-component system developer of the present invention includes a magnetic carrier used for an electrophotographic developer which can exhibit a good durability, is free from occurrence of carrier adhesion, and can maintain a high quality of images produced for a long period of time, and comprises the magnetic carrier for an electrophotographic developer and a toner.