Developer Toner and Carrier for Image Density Control
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Solution Overview
Problem
Existing image forming apparatuses face challenges in achieving desired image density and minimizing fogging due to issues with toner charge stability and carrier degradation, particularly in the initial stages of use.
Innovation Solution
A developer comprising toner particles with external additive particles, including silica and spacer particles, and carrier particles with strontium titanate and barium titanate, where the spacer particles have a specific size and coverage ratio to maintain charge stability and prevent excessive charge accumulation, and the carrier particles have a coat layer with barium titanate for improved electrostatic capacity and reduced abrasion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a carrier is used to inhibit toner attachment to non-image areas, then fogging is reduced, but toner charge stability deteriorates and carrier degradation occurs
Solution Approach 1:
The invention changes the particle size parameters of the carrier, specifically setting the volume median diameter to 15.0 μm or more and 65.0 μm or less, and adjusting the saturation magnetization to 65 emu/g or more and 90 emu/g or less. These parameter optimizations improve toner charge stability while maintaining fogging prevention capabilities.
Solution Approach 2:
The carrier is constructed as a composite material with a magnetic core (such as ferrite) and a resin coat layer. This composite structure combines the magnetic properties needed for charge control with the protective properties of the resin layer, reducing carrier degradation while maintaining effective toner attachment control.
2Object-affected harmful factors
If carrier particle size is increased to reduce toner attachment, then fogging is reduced, but carrier life decreases due to increased abrasion
Solution Approach 1:
The invention optimizes the carrier particle size parameter by setting the volume median diameter within a specific range (15.0 μm to 65.0 μm). This parameter optimization achieves effective toner attachment control while reducing mechanical stress and abrasion, thereby extending carrier life.
Solution Approach 2:
The resin coat layer in the composite carrier structure provides protective properties that reduce abrasion and wear during operation. This extends the carrier life while the magnetic core maintains the necessary magnetic properties for controlling toner attachment to non-image areas.
3Reliability
If carrier saturation magnetization is increased to improve charge control, then toner attachment control is improved, but carrier durability decreases
Solution Approach 1:
The invention changes the saturation magnetization parameter to an optimized range of 65 emu/g to 90 emu/g. This parameter adjustment provides sufficient magnetic control for effective toner attachment management while avoiding excessive magnetic strength that would cause carrier degradation and reduce durability.
Solution Approach 2:
The composite structure with magnetic core and resin coat layer allows the magnetic core to provide necessary charge control within the optimized magnetization range, while the resin coat layer protects the carrier from degradation, maintaining durability during extended operation.
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 enables the formation of images with desired image density and reduced fogging by stabilizing toner charge and extending carrier life, while also reducing the frequency of carrier replacement in the development device.
Implementation Method 1
The coating resin includes silicone resin. The barium titanate particles have a number average primary particle diameter of at least 100 nm and no greater than 500 nm.
Implementation Method 2
The carrier particles each include a carrier mother particle and strontium titanate particles attached to a surface of the carrier mother particle. The strontium titanate particles have a number average primary particle diameter of at least 15 nm and no greater than 85 nm.
Implementation Method 3
The external additive particles include first silica particles and spacer particles. The first silica particles have a number average primary particle diameter of at least 10 nm and no greater than 30 nm.
Data Source
AI summary
A developer includes a toner containing toner particles and a carrier containing carrier particles. The toner particles each include a toner mother particle and external additive particles attached to a surface of the toner mother particle. The external additive particles include first silica particles and spacer particles. The first silica particles have a number average primary particle diameter of at least 10 nm and no greater than 30 nm. The spacer particles have a number average primary particle diameter of at least 32 nm and no greater than 145 nm. The spacer particles in the toner particles have a coverage ratio of at least 2.0% by area and no greater than 40.0% by area. The carrier particles each include a carrier mother particle and strontium titanate particles attached to a surface of the carrier mother particle.