Toner Charge Distribution via Localized Particle Coverage
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Solution Overview
Problem
Toner particles of small size exhibit a trade-off between image density stability and fogging suppression in high-temperature, high-humidity environments, with issues of low electric field strength and increased fogging due to uniform surface charge density and embedding of inorganic fine particles, while toners with adjusted silica coverage ratios suffer from pronounced fogging and decreased charging performance.
Innovation Solution
A toner comprising a binder resin and a polyolefin resin with a neutralized carboxy group, where the content ratio of monomer units containing —COOM is between 1 mass % to 20 mass %, and the toner is divided into two groups with distinct particle sizes, optimizing the charge distribution and surface charge density to enhance image density stability and suppress fogging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If uniform coverage of shell layer and inorganic fine particles is applied to all toner particles, then manufacturing simplicity is maintained, but charge quantity per particle decreases for small particles and fogging occurs in high-temperature high-humidity environments
Solution Approach 1:
The patent applies different coverage ratios of inorganic fine particles to different particle size ranges. Specifically, toner particles with diameter of 0.5 μm or more have a coverage ratio of 5-20 mass%, while particles with diameter less than 0.5 μm have a coverage ratio of 10-30 mass%. This local differentiation ensures that small particles receive sufficient charge to prevent fogging while larger particles maintain appropriate charge levels for image density stability.
2Object-affected harmful factors
If coverage ratio of inorganic fine particles is increased to improve charging performance, then fogging is suppressed, but image density decreases due to excessively large charge quantity on coarse powder
Solution Approach 1:
The patent implements differentiated coverage ratios based on particle size: 5-20 mass% for particles ≥0.5 μm and 10-30 mass% for particles <0.5 μm. This resolves the contradiction by ensuring fine particles have sufficient charge to prevent fogging while coarse particles maintain moderate charge levels to preserve image density stability.
3Manufacturing precision
If toner particle size is reduced to improve dot reproducibility, then image quality is enhanced, but charge quantity per particle decreases and fogging occurs in high-temperature high-humidity environments
Solution Approach 1:
The patent addresses the fogging issue of fine particles by applying a higher coverage ratio of inorganic fine particles (10-30 mass%) to particles with diameter less than 0.5 μm. This compensates for the reduced charge quantity per particle in fine particles, ensuring sufficient electrostatic force to prevent fogging while maintaining the small particle size needed for dot reproducibility.
4Object-affected harmful factors
If charge quantity is increased to prevent fogging, then fogging suppression is improved, but electrostatic attachment forces increase and image density decreases
Solution Approach 1:
The patent applies higher charge quantity (10-30 mass% inorganic fine particles) only to fine particles that are prone to fogging, while maintaining moderate charge quantity (5-20 mass%) on coarse particles. This localized approach suppresses fogging where needed without causing excessive electrostatic attachment that would reduce image density.
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 achieves superior image density stability and reduced fogging by optimizing charge distribution and surface charge density, improving the toner's responsiveness and performance in varying environmental conditions.
Implementation Method 1
a polyolefin resin having —COOM that is a neutralized carboxy group with a monovalent metal ion M... optimizing the charge distribution and surface charge density
Data Source
AI summary
A toner containing a toner particle that contains a binder resin including a polyester resin, and a polyolefin resin having —COOM that is a neutralized carboxy group with a monovalent metal ion M, wherein the polyolefin resin having —COOM is a polymer in which a vinyl polymer is bonded to a polyolefin, a content of a monomer unit containing —COOM in the polyolefin resin having —COOM is 1 to 20 mass %, and in a FT-IR spectrum obtained through measurement of a large particle size-side particle group and a small particle size-side particle group obtained by dividing the toner into two substantially equal parts, on a number basis, a ratio of the intensity of a maximum absorption peak in a range from 1545 cm−1 to 1555 cm−1 with respect to the intensity of a maximum absorption peak in a range from 1713 cm−1 to 1723 cm−1 exhibits a specific relationship.