Toner Particle Circularity and Size Distribution for Transfer Efficiency
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Solution Overview
Problem
Existing toners for electrophotographic systems face challenges in achieving a balance between transfer efficiency and cleanability, with high average circularity leading to poor transfer residual removal and low image density, especially during long-term printing.
Innovation Solution
A toner with a weight average particle diameter of 3.0 μm to 8.0 μm, characterized by an average circularity of 0.960 to 0.985 and a limited proportion of particles with circularity 0.990 or more (25% or less), optimized using a specific binder resin and wax composition, and a heat treatment process to control particle distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the average circularity of toner particles is increased to improve transfer efficiency, then transfer efficiency is improved, but cleanability deteriorates due to poor removal of transfer residuals
Solution Approach 1:
The patent applies local quality by creating a bimodal particle size distribution where different particle sizes serve different functions. The first particle size range (4.0-8.0 μm) provides good transfer efficiency and cleanability, while the second particle size range (0.5-2.0 μm) fills gaps and improves image density. This local differentiation of particle functions resolves the contradiction between transfer efficiency and cleanability.
Solution Approach 2:
The patent segments the toner particle population into two distinct size groups with specific circularity requirements. By dividing particles into larger (4.0-8.0 μm) and smaller (0.5-2.0 μm) categories with different circularity specifications, the patent enables each segment to optimize for its specific function, resolving the transfer efficiency-cleanability contradiction.
2Illumination intensity
If small particles with diameter less than 2 μm are increased in number to improve image density, then image density is improved, but the surface of magnetic carrier is spent and image density is reduced after prolonged printing
Solution Approach 1:
The patent applies parameter changes by precisely controlling the particle size distribution parameters. The smaller particles are limited to 0.5-2.0 μm (previously unrestricted), and their proportion is controlled at 10% or less by number. This parameter restriction prevents excessive wear on the magnetic carrier while maintaining image density benefits.
Solution Approach 2:
The patent uses partial action by including a small controlled amount of fine particles (0.5-2.0 μm) rather than excluding them completely or allowing unlimited quantities. This partial inclusion provides the image density benefits of fine particles while limiting their harmful effect on carrier durability.
3Productivity
If the proportion of particles with circularity 0.990 or more is increased to improve transfer efficiency, then transfer efficiency is improved, but cleanability deteriorates
Solution Approach 1:
The patent applies local quality by specifying different circularity requirements for different particle size ranges. Larger particles (4.0-8.0 μm) require circularity of 0.950 or more for good transfer efficiency, while smaller particles (0.5-2.0 μm) require higher circularity of 0.970 or more. This differentiated local quality specification resolves the contradiction between transfer efficiency and cleanability.
Data Source
AI summary
It is an object of the present invention to provide a toner having the transfer efficiency and the cleanability in combination, exhibiting excellent stress resistance, and ensuring the low-temperature fixing.A toner characterized in that the average circularity of the above-described toner is 0.960 or more, and 0.985 or less, where the average circularity is analyzed by dividing particles having a circle equivalent diameter of 1.98 μm or more, and 200.00 μm or less, the number A of toners having a circularity of 0.990 or more, and 1.000 or less is 25.0 percent by the number or less, and the percentage of the number of particles B having a circle equivalent diameter of 0.50 μm or more, and 1.98 μm or less relative to the total particles of 0.50 μm or more, and 200.00 μm or less is 10.0 percent by the number or less.