Toner Particle Circularity and Additive Aspect Ratio for Density Uniformity

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Solution Overview

Problem

Existing electrostatic charge image developing toners face issues with density unevenness due to the embedding of external additives in high-temperature and high-humidity environments, leading to deteriorated toner developing properties and increased toner density, which results in inconsistent image quality.

Innovation Solution

The use of toner particles with an average circularity of 0.96 to 1.00 and organic particles with an aspect ratio of 0.4 to 0.9 as external additives, which prevents the closest packing between toner particles and the carrier, maintaining high bulk density and preventing density unevenness by ensuring proper fluidity and replacement of the developer in the developing unit.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional toner particles with lower circularity and spherical external additives are used, then manufacturing is easier and cost is lower, but density unevenness occurs due to embedding of additives in high-temperature and high-humidity environments

Engineering Contradiction:

Improveimage quality consistencyVSAvoidtoner particle shape control

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent changes the geometric parameters of both toner particles (average circularity 0.94 or more) and external additives (aspect ratio 0.7 or more) to prevent closest packing. This parameter optimization ensures that particles cannot pack densely, thereby preventing embedding of additives in the toner layer and maintaining consistent image quality in high-temperature and high-humidity environments.

Inventive Principle:

Principle #35Parameter changes

2Ease of operation

If spherical external additives are used, then fluidity is improved, but closest packing between toner particles and carrier occurs leading to density unevenness

Engineering Contradiction:

Improvedeveloper fluidityVSAvoidtoner developing properties

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent optimizes the aspect ratio of external additives to 0.7 or more (approaching spherical but not perfectly spherical) and toner particle circularity to 0.94 or more. This specific parameter range maintains sufficient fluidity for developer operation while preventing the closest packing that causes density unevenness and embedding of additives.

Inventive Principle:

Principle #35Parameter changes

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

This configuration effectively prevents density unevenness by maintaining high bulk density and ensuring consistent toner supply, thereby improving image quality and reducing the occurrence of density-related issues in electrostatic charge image development.

Implementation Method 1

prevents the closest packing between toner particles and the carrier, maintaining high bulk density

Methodology Applied

Scientific EffectPacking efficiency: Close Packing

Implementation Method 2

an electrostatic charge image is formed as image information on the surface of an image holding member through charging

Methodology Applied

Scientific EffectElectrostatic charging: Electrostatics

Data Source

PatentUS11506989B2Electrostatic charge image developing toner and electrostatic charge image developer

Publication Date: 2022.11.22 FUJIFILM BUSINESS INNOVATION CORP

AI summary

An electrostatic charge image developing toner includes toner particles having an average circularity of 0.96 to 1.00 and organic particles having an aspect ratio of 0.4 to 0.9 as an external additive.