Toner Particle Circularity and Charging Stability

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Solution Overview

Problem

Conventional electrophotographic toners with irregularly shaped particles suffer from poor charging performance and image quality due to inadequate dispersion of colorants and charge control agents, leading to issues like background fouling and decreased image quality.

Innovation Solution

A toner with toner base particles having an average circularity of 0.850 to 0.950, containing a binder resin, release agent, and charge control agent, along with an external additive of inorganic particles such as barium sulfate, magnesium hydroxide, or magnesium oxide with a diameter between 350 to 1000 nm, ensuring consistent charging performance and improved image quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If toner particles are reduced to ultrafine size (3 μm or less) to improve image segment reproducibility, then image quality improves, but particle shape irregularity increases leading to poor charging performance and conveyance failure

Engineering Contradiction:

Improveimage segment reproducibilityVSAvoidcharging performance

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent applies spheroidality by using spherical silica particles as external additives to promote spherization of toner particles. The spherical shape of the external additive particles serves as a template during coating, inducing the toner particles to adopt more spherical shapes with higher circularity (0.93 or more), which improves both charging performance and conveyance reliability while maintaining ultrafine size for good image segment reproducibility

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Ease of manufacture

If colorants and charge control agents are added to thermoplastic resin to create toner, then toner functionality is achieved, but inadequate dispersion occurs leading to fracture interfaces and abnormally shaped particles

Engineering Contradiction:

Improvetoner productionVSAvoidparticle shape uniformity

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent applies composite materials by combining thermoplastic resin with inorganic silica particles as external additives. This composite structure improves particle shape uniformity because the silica particles form a rigid spherical framework that maintains spherical shape even after cooling and handling, preventing the formation of abnormally shaped particles with low circularity

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent applies parameter changes by controlling the particle size of silica external additives within a specific range (0.3-1.0 μm) and optimizing the coating amount (0.1-5.0 parts by mass per 100 parts by mass of toner). These parameter optimizations ensure uniform particle shape while maintaining good dispersion of colorants and charge control agents in the thermoplastic resin matrix

Inventive Principle:

Principle #35Parameter changes

3Reliability

If external additives are used to impart fluidity and charging properties to toner, then charging performance improves, but particle size reduction and spherization become more difficult to control

Engineering Contradiction:

Improvecharging propertiesVSAvoidparticle size control

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent applies local quality by concentrating the external additive function specifically on the particle surface through controlled coating. The silica particles are applied as external additives that primarily affect the surface properties of toner particles, providing charging sites and fluidity without significantly affecting the core particle size distribution. This localized application allows independent optimization of charging properties and particle size control

Inventive Principle:

Principle #3Local quality

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 toner maintains stable charging performance over time, reducing background fouling and enhancing image quality by ensuring uniform particle shape and distribution, thereby producing high-quality images for extended periods.

Implementation Method 1

using external additives with an average primary particle diameter of several to several tens of nanometers can impart fluidity and charging properties to the toner

Methodology Applied

Scientific EffectFriction: Friction

Implementation Method 2

using external additives with an average primary particle diameter of several to several tens of nanometers can impart fluidity and charging properties to the toner

Methodology Applied

Scientific EffectElectrostatic charge: Electrostatics

Data Source

PatentUS20240393707A1Toner, toner accommodating unit, image forming apparatus, and image forming method

Publication Date: 2024.11.28 RICOH CO LTD

AI summary

A toner contains toner base particles, each containing a binder resin, a release agent, and a charge control agent, and an external additive, wherein the toner base particles have an average circularity of from 0.850 to 0.950, and the external additive contains at least an inorganic particle selected from the group consisting of barium sulfate, magnesium hydroxide, and magnesium oxide, each having an average circularity of from 350 to 1,000 nm.