Toner Particle Void Distribution for Crack Resistance
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Solution Overview
Problem
Existing toners for electrophotography suffer from image defects such as development streaks and fogging due to cracking and chipping of toner particles under stress, especially in high-temperature and high-humidity environments, and contamination from wax exudation, which are not adequately addressed by previous methods that control void sizes and ratios.
Innovation Solution
A toner with a specific composition and production method that includes a binder resin, colorant, and wax, where the proportion of voids with diameters of 0.50 μm or less is 60% or more, and voids within 1.00 μm from the surface are minimized, using a granulation process with circulation flow and defoaming to reduce surface voids and encapsulate wax, preventing cracking and contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If toner particles contain a large number of voids to improve fixing performance, then fixing performance is improved, but toner particles crack under shear stress causing development streaks and image defects
Solution Approach 1:
The patent applies local quality by creating different void distributions in different regions of the toner particle. The surface region has fewer and smaller voids to provide strength and prevent cracking, while the interior region contains more voids to maintain fixing performance. This spatial differentiation of void characteristics resolves the contradiction between needing voids for fixing performance and avoiding them for structural strength.
2Reliability
If voids are present in the vicinity of the surface layer of toner particles, then fixing performance is enhanced, but surface chipping occurs leading to wax exudation and contamination of parts
Solution Approach 1:
The patent implements local quality by strictly controlling the void-free zone within 1.00 μm of the surface. This creates a protective surface layer that prevents chipping and wax exudation while allowing voids to exist in the interior region for fixing performance. The spatial separation of voids from the surface region eliminates the harmful effects while preserving benefits.
3Strength
If the proportion of voids with long diameter of 0.50 μm or less is increased to 60% or more, then resistance to stress is improved, but image quality deteriorates due to insufficient stress resistance when large voids are present
Solution Approach 1:
The patent applies parameter changes by specifying precise quantitative parameters: void long diameter of 0.50 μm or less, proportion of 60% or more, and positioning within 1.00 μm from surface for no more than 30% of voids. These parameter specifications ensure optimal stress resistance while maintaining image quality by preventing both cracking and wax exudation.
4Ease of manufacture
If simple control of average diameter of bubbles in shell layer is used, then manufacturing is simplified, but cracking and chipping of toner particles cannot be sufficiently suppressed
Solution Approach 1:
The patent moves from simple average diameter control to precise parameter specification including void size (0.50 μm or less), proportion (60% or more), and position relative to surface (within 1.00 μm for no more than 30%). This enhanced parameter control achieves sufficient cracking suppression while remaining manufacturable.
Data Source
AI summary
A toner has a toner particle including a binder resin, a colorant, and a wax, in which in a cross section of the toner particle observed under a scanning transmission electron microscope, a proportion of the number of toner particles having a void with a long diameter of 0.50 μm or less is 60 number % or more, and a proportion of the number of toner particles having a void in a region from an outline of the cross section of the toner particle inward to 1.00 μm in a total number of the toner particles having a void is 30 number % or less.