Core-Shell Toner Composition for Humidity-Stable Image Density
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Solution Overview
Problem
Existing toner production methods fail to prevent or reduce image density unevenness in high temperature-high humidity environments due to charge injection issues.
Innovation Solution
A toner production method involving a core-shell structure formed by aggregating and coalescing amorphous resin particles, with controlled elemental sulfur content between 0.05% to 0.20% by mass, to facilitate moisture retention and reduce charge injection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional toner production methods are used, then manufacturing process is simple, but image density unevenness occurs in high temperature-high humidity environments due to charge injection
Solution Approach 1:
The patent applies parameter changes by precisely controlling the elemental sulfur content within 0.05-0.20 mass% and the glass transition temperature difference (Tg2-Tg1) between 5-40°C. These parameter optimizations resolve the contradiction by enabling stable charge distribution and moisture retention that prevent image density unevenness, while maintaining a feasible production process through controlled coalescing of resin fine particles onto core particles
Solution Approach 2:
The patent employs composite materials by creating a toner structure with core particles containing binder resin, colorant, and release agent, coated with a shell layer formed from resin fine particles containing carboxyl and sulfonic acid groups. This composite structure with specific sulfur content (0.005-0.050 mass% in coating layer) provides both the complexity needed for reliability and the performance stability required for high temperature-high humidity environments
2Reliability
If resin fine particles are added to form coating layer, then charge distribution is stabilized, but production process complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-forming core particles with specific properties (binder resin, colorant, release agent) before coating them with resin fine particles. The resin fine particles are prepared in advance with controlled glass transition temperature and chemical groups (carboxyl and sulfonic acid). This sequential preparation resolves the contradiction by establishing stable charge distribution through the pre-configured coating layer while organizing the production process into manageable discrete steps
Solution Approach 2:
The patent applies local quality by creating distinct regions with different properties: core particles with specific composition and a coating layer with resin fine particles containing carboxyl and sulfonic acid groups. The elemental sulfur is locally concentrated in the coating layer (0.005-0.050 mass%) rather than uniformly distributed. This local differentiation stabilizes charge distribution at the particle surface while allowing the production process to target specific regions for modification
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
Prevents or reduces image density unevenness by maintaining moisture within the toner particles, thereby stabilizing charge distribution and improving image quality.
Implementation Method 1
fusing and coalescing the second aggregated particles into toner particles by heating a dispersion containing the second aggregated particles
Implementation Method 2
maintaining moisture within the toner particles, thereby stabilizing charge distribution and improving image quality
Data Source
AI summary
A method for producing a toner for developing electrostatic charge images includes: forming first aggregated particles by aggregating amorphous resin particles (1), which are obtained by melt-mixing an amorphous resin and adding an aqueous medium to effect granulation, in a resin particle dispersion containing the amorphous resin particles (1); forming second aggregated particles by attaching amorphous resin particles (2), which are obtained by dissolving and mixing an amorphous resin with an organic solvent and adding an aqueous medium to effect granulation, to surfaces of the first aggregated particles in a resin particle dispersion containing the first aggregated particles and the amorphous resin particles (2); and fusing and coalescing the second aggregated particles into toner particles by heating a dispersion containing the second aggregated particles, in which the toner particles contain elemental sulfur, and an elemental sulfur content in the toner particles is 0.05 mass % or more and 0.20 mass % or less relative to a mass of the toner particles.