Toner Additive Segmentation for Charge Stability

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Solution Overview

Problem

Existing image forming apparatuses face issues with maintaining excellent image density and uniformity over time, due to rapid changes in the electric charge amount of the developer, leading to problems like poor image density at the early stage of use and increased hue changes.

Innovation Solution

The image forming apparatus uses a two-component developer system where the initial toner contains a fine powder prepared by adding silica to strontium titanate and hydrophobizing the surface with a silane compound, and the replenishment toner contains titanium dioxide and silica particles. This configuration ensures a stable electric charge amount by controlling the adhesion strengths and particle diameters of the external additives.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the toner is designed to have high electric charge amount at the early stage of use to compensate for charge decrease over time, then the electric charge amount is secured at advanced product lifespan, but poor image density occurs at the early stage of use and increased change in hue occurs

Engineering Contradiction:

Improveelectric charge amount stabilityVSAvoidimage density uniformity

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The toner supply system is segmented into initial toner and replenishment toner with different compositions. The initial toner contains fine powder (silica-strontium titanate composite) for early stage charge stability, while the replenishment toner contains titanium dioxide particles for long-term charge stability. This segmentation allows each toner type to be optimized for its specific usage phase, resolving the contradiction between early stage image quality and long-term charge stability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The external additive composition parameters are changed between initial and replenishment toners. Specifically, the fine powder content is controlled at 0.1-5 mass% in initial toner and 0.01-2 mass% in replenishment toner, while titanium dioxide content is 0.01-2 mass% in initial toner and 0.1-5 mass% in replenishment toner. These parameter changes enable the system to achieve both good early stage image density and stable long-term charge amount.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If different external additives are used between initial toner and replenishment toner, then the electric charge amount can be stabilized over time, but the initial toner and replenishment toner are insufficiently agitated resulting in poor uniformity in image density and fogging

Engineering Contradiction:

Improveelectric charge amount stabilityVSAvoidimage density uniformity

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

Silica particles serve as an intermediary component present in both initial and replenishment toners. The silica particles (0.1-5 mass% in initial toner, 0.1-3 mass% in replenishment toner) act as a common element that facilitates proper agitation and mixing between the two toner types, preventing fogging and ensuring uniform image density while still allowing the different external additives (fine powder vs. titanium dioxide) to provide their respective charge stability functions.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The external additive system uses composite materials: strontium titanate particles coated with silica in the initial toner, and titanium dioxide particles coated with silica in the replenishment toner. This composite structure combines the charge stability benefits of strontium titanate/titanium dioxide with the agitation-enhancing properties of silica, achieving both charge stability and image uniformity.

Inventive Principle:

Principle #40Composite materials

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 approach effectively maintains excellent image density and uniformity over a long period, suppresses fogging, and stabilizes the electric charge amount, ensuring high-quality image formation.

Implementation Method 1

hydrophobizing a surface of the core with a silane compound

Methodology Applied

Scientific EffectHydrophobization: Hydrophobe

Implementation Method 2

a charge control agent having a high charging stability, such as a titanium dioxide (titanium (IV) oxide) particle

Methodology Applied

Scientific EffectElectrostatic charge control: Electrostatics

Data Source

PatentUS20250044717A1Image forming apparatus

Publication Date: 2025.02.06 SHARP KK

AI summary

In an image forming apparatus, a two-component developer including an initial toner and a carrier is previously charged into a developer tank, and a replenishment toner is replenished into the developer tank as the development proceeds. The image forming apparatus has the following configuration. The initial toner contains, as external additives, a fine powder prepared by adding silica to strontium titanate to form a core and hydrophobizing a surface of the core with a silane compound, and a silica particle, and does not contain any titanium dioxide particle or contains a titanium dioxide particle at 50% by mass or less of the fine powder. The replenishment toner contains, as external additives, a titanium dioxide particle and a silica particle, and does not contain the fine powder or contains the fine powder at 50% by mass or less of the titanium dioxide particle.