Magnetic Toner Core-Shell Structure for Fixability
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Solution Overview
Problem
Existing magnetic toners face challenges in maintaining low-temperature fixability and preventing toner melting unevenness and electrostatic offset, especially in harsh environments, due to uneven distribution of magnetic bodies and low affinity between crystalline polyester and binder resin, leading to reduced tinting strength and image density uniformity.
Innovation Solution
A magnetic toner with controlled dispersion of magnetic bodies and crystalline polyester, where the storage elastic modulus is adjusted within specific ranges to ensure uniform distribution and improved adhesion, using a core-shell structure and specific formulations of binder resin and crystalline polyester to enhance low-temperature fixability and prevent electrostatic offset.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If magnetic bodies are uniformly dispersed inside the toner by controlling acid value and hydroxy value of binder resin, then dispersibility of magnetic bodies is improved, but magnetic bodies are exposed on the toner surface and charge quantity cannot be maintained in high-temperature and high-humidity environment
Solution Approach 1:
The invention applies local quality by creating a core-shell structure where the surface layer has different composition and properties from the interior. The surface layer contains binder resin with specific acid value and hydroxy value that prevents magnetic body exposure, while the interior maintains uniform magnetic body dispersion. This local differentiation resolves the contradiction by protecting the magnetic bodies where needed while maintaining dispersibility where required.
Solution Approach 2:
The invention uses composite materials by combining binder resins with different acid values and hydroxy values in specific proportions. The surface layer uses binder resin with acid value 0.1-0.5 mmol/g and hydroxy value 0.1-0.5 mmol/g, while the interior uses binder resin with different parameters. This composite approach allows simultaneous achievement of good dispersibility and charge maintenance reliability.
2Temperature
If a large amount of crystalline polyester is added to improve low-temperature fixability, then low-temperature fixability is improved, but dispersibility of magnetic bodies is lowered and magnetic bodies aggregate inside the toner
Solution Approach 1:
The invention applies local quality by concentrating crystalline polyester in the surface layer rather than uniformly distributing it throughout the toner particle. The surface layer contains crystalline polyester with melting point 50-90°C that provides low-temperature fixability, while the interior maintains good magnetic body dispersibility. This localized approach resolves the contradiction by providing heat-induced flow where needed without causing magnetic body aggregation.
Solution Approach 2:
The invention uses parameter changes by controlling the melting point of crystalline polyester to be 50-90°C and adjusting the acid value and hydroxy value of binder resin. These parameter optimizations allow the crystalline polyester to provide low-temperature fixability while maintaining magnetic body dispersibility through proper compatibility control.
3Stability of the object's composition
If affinity between crystalline polyester and magnetic bodies is low, then dispersibility is improved, but exposure of magnetic bodies on toner surface and charge leaks occur
Solution Approach 1:
The invention applies local quality by creating a surface layer with specific binder resin composition that has appropriate affinity for magnetic bodies. The surface layer uses binder resin with acid value 0.1-0.5 mmol/g and hydroxy value 0.1-0.5 mmol/g that provides sufficient affinity to prevent magnetic body exposure and charge leaks, while the interior maintains optimal dispersibility.
Solution Approach 2:
The invention uses composite materials by combining binder resins with different acid values and hydroxy values. The surface layer uses binder resin with lower acid value and hydroxy value (0.1-0.5 mmol/g) that provides appropriate affinity to prevent charge leaks, while the overall composite structure maintains good dispersibility.
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 toner achieves excellent low-temperature fixability, improved adhesion, and reduced electrostatic offset, maintaining image quality and density uniformity even in harsh environments, by optimizing the dispersion state of magnetic bodies and the elastic modulus of the toner.
Implementation Method 1
a crystalline polyester producing a high effect on low-temperature fixability has the property of easily becoming compatible with the binder resin in the vicinity of the melting point thereof, and the toner including the crystalline polyester is easily melted and deformed rapidly at the time of fixing
Implementation Method 2
the toner including magnetic bodies is conveyed by rotating the bearing member incorporating a magnet
Implementation Method 3
the surface adhesion between the toner particles becomes insufficient when the toner is fixed at a low temperature
Data Source
AI summary
A magnetic toner comprising a magnetic toner particle including a binder resin, a magnetic body and a crystalline polyester, wherein in cross-sectional observation of the magnetic toner particle using a transmission electron microscope, a variation coefficient CV3 of an occupied area ratio of the magnetic body when a cross section of the magnetic toner particle is divided by a square grid having a side of 0.8 μm is from 40.0% to 80.0%, and assuming that a storage elastic modulus at 40° C. is taken as E′(40) [Pa] and a storage elastic modulus at 85° C. is taken as E′(85) [Pa], the storage elastic moduli being obtained in a powder dynamic viscoelasticity measurement of the magnetic toner, the following formulas (1) and (2) are satisfied.E′(85)≤2.0×109 (1)[E′(40)−E′(85)]×100/E′(40)≥70 (2)