Developing Roller and Toner Composition for Stable Charge Injection

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Solution Overview

Problem

Existing developing systems face challenges in maintaining stable charge injection performance in high-speed processes due to issues with toner and developing roller interactions, particularly under varying humidity conditions and high-speed operations, leading to problems like fogging and toner scattering.

Innovation Solution

A developing apparatus with a toner containing titanium atom-containing fine particles and a developing roller having a specific conductive surface layer and metal film configuration, along with controlled impedance and surface electric potential, to ensure stable charge injection and retention.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a large amount of external additives is used to improve charge injection performance, then charging performance is improved, but external additives submerge during high-speed operation causing charge leakage and fogging

Engineering Contradiction:

Improvecharge injection performanceVSAvoidcharge leakage and fogging

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent changes the physical and chemical parameters of the external additive by specifying precise particle size ranges (0.1-10 μm diameter) and chemical composition (metal oxide with specific surface area 1-100 m²/g). This optimization ensures sufficient charge injection while preventing submersion during high-speed operation, resolving the contradiction between charging performance and charge leakage.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite toner system combining toner particles with specifically engineered external additives (metal oxide fine particles with controlled surface area and size). This composite structure provides stable charge injection performance while preventing additive submersion, thereby eliminating fogging and charge leakage issues.

Inventive Principle:

Principle #40Composite materials

2Device complexity

If triboelectric charging is used to charge toner, then charging process is simple, but charging amount varies with humidity and toner flowability

Engineering Contradiction:

Improvecharging process complexityVSAvoidcharging stability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent replaces the mechanical triboelectric charging process with an electric field-based charge injection process. By applying an electric field between the developing roller and toner, charge is injected directly into the toner particles without mechanical contact. This substitution eliminates the influence of humidity and flowability on charging stability while maintaining process simplicity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Productivity

If high-speed developing process is used to increase productivity, then output speed is improved, but external additives submerge causing charging performance reduction

Engineering Contradiction:

Improvedeveloping speedVSAvoidcharging performance stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent performs preliminary optimization of the external additive properties before high-speed operation begins. By pre-setting the particle size (0.1-10 μm) and surface area (1-100 m²/g) parameters, the system is prepared to maintain stable charge injection performance even under high-speed developing conditions, preventing additive submersion and performance degradation.

Inventive Principle:

Principle #10Preliminary action

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 solution achieves stable charge injection and retention without using excessive external additives, preventing charge leakage and excessive charging, thus maintaining image quality in high-speed operations.

Implementation Method 1

an injection charging process is a process of charging toner by injecting electric charge in accordance with an electric potential difference between the toner and a charging member

Methodology Applied

Scientific EffectCharge injection: Electrostatic Induction

Implementation Method 2

a corona discharger having a grid portion of which a width is 3.0 mm is arranged such that a distance between the grid portion and the outer surface of the developing roller is 1.0 mm

Methodology Applied

Scientific EffectCorona discharge: Corona Discharge

Implementation Method 3

If there is a conduction path in a toner or between toners, not only a portion in contact with a charging member but also the entire toner can be uniformly charged

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentUS20260064037A1Developing apparatus, process cartridge, and electrophotographic image forming apparatus

Publication Date: 2026.03.05 CANON KK

AI summary

A developing apparatus including: a toner configured to have toner particle and external additive; a toner carrying member configured to carry the toner; and an charge injection member configured to inject electric charge into the toner, in which the external additive contain titanium atom-containing fine particles containing a compound containing titanium atoms, a presence ratio of the titanium atoms is 0.05 to 4.00 atomic % when a surface of the toner is measured using X-ray photoelectron spectroscopy, the toner carrying member is a developing roller having a substrate having a conductive outer surface and a resin layer on the outer surface of the substrate, impedance of the developing roller measured under specific conditions is 1.00×106 Ω or more, and a maximum value of a surface potential measured under specific conditions is less than 20.0 V.